[v2,1/4] drm/amdgpu/mst: Stop ignoring error codes and deadlocking

  It appears that amdgpu makes the mistake of completely ignoring the return
values from the DP MST helpers, and instead just returns a simple
true/false. In this case, it seems to have come back to bite us because as
a result of simply returning false from
compute_mst_dsc_configs_for_state(), amdgpu had no way of telling when a
deadlock happened from these helpers. This could definitely result in some
kernel splats.

V2:
* Address Wayne's comments (fix another bunch of spots where we weren't
  passing down return codes)

Signed-off-by: Lyude Paul <lyude@redhat.com>
Fixes: 8c20a1ed9b4f ("drm/amd/display: MST DSC compute fair share")
Cc: Harry Wentland <harry.wentland@amd.com>
Cc: <stable@vger.kernel.org> # v5.6+
---
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |  18 +-
 .../display/amdgpu_dm/amdgpu_dm_mst_types.c   | 235 ++++++++++--------
 .../display/amdgpu_dm/amdgpu_dm_mst_types.h   |  12 +-
 3 files changed, 147 insertions(+), 118 deletions(-)
  

[Public]

All the patch set looks good to me. Feel free to add:
Reviewed-by: Wayne Lin <Wayne.Lin@amd.com>

Again, thank you Lyude for helping on this!!!

Regards,
Wayne
> -----Original Message-----
> From: Lyude Paul <lyude@redhat.com>
> Sent: Tuesday, November 15, 2022 6:18 AM
> To: amd-gfx@lists.freedesktop.org
> Cc: Wentland, Harry <Harry.Wentland@amd.com>; stable@vger.kernel.org;
> Li, Sun peng (Leo) <Sunpeng.Li@amd.com>; Siqueira, Rodrigo
> <Rodrigo.Siqueira@amd.com>; Deucher, Alexander
> <Alexander.Deucher@amd.com>; Koenig, Christian
> <Christian.Koenig@amd.com>; Pan, Xinhui <Xinhui.Pan@amd.com>; David
> Airlie <airlied@gmail.com>; Daniel Vetter <daniel@ffwll.ch>; Kazlauskas,
> Nicholas <Nicholas.Kazlauskas@amd.com>; Pillai, Aurabindo
> <Aurabindo.Pillai@amd.com>; Li, Roman <Roman.Li@amd.com>; Zuo, Jerry
> <Jerry.Zuo@amd.com>; Wu, Hersen <hersenxs.wu@amd.com>; Lin, Wayne
> <Wayne.Lin@amd.com>; Thomas Zimmermann <tzimmermann@suse.de>;
> Mahfooz, Hamza <Hamza.Mahfooz@amd.com>; Hung, Alex
> <Alex.Hung@amd.com>; Mikita Lipski <mikita.lipski@amd.com>; Liu,
> Wenjing <Wenjing.Liu@amd.com>; Francis, David
> <David.Francis@amd.com>; open list:DRM DRIVERS <dri-
> devel@lists.freedesktop.org>; open list <linux-kernel@vger.kernel.org>
> Subject: [PATCH v2 1/4] drm/amdgpu/mst: Stop ignoring error codes and
> deadlocking
> 
> It appears that amdgpu makes the mistake of completely ignoring the return
> values from the DP MST helpers, and instead just returns a simple true/false.
> In this case, it seems to have come back to bite us because as a result of
> simply returning false from compute_mst_dsc_configs_for_state(), amdgpu
> had no way of telling when a deadlock happened from these helpers. This
> could definitely result in some kernel splats.
> 
> V2:
> * Address Wayne's comments (fix another bunch of spots where we weren't
>   passing down return codes)
> 
> Signed-off-by: Lyude Paul <lyude@redhat.com>
> Fixes: 8c20a1ed9b4f ("drm/amd/display: MST DSC compute fair share")
> Cc: Harry Wentland <harry.wentland@amd.com>
> Cc: <stable@vger.kernel.org> # v5.6+
> ---
>  .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |  18 +-
>  .../display/amdgpu_dm/amdgpu_dm_mst_types.c   | 235 ++++++++++------
> --
>  .../display/amdgpu_dm/amdgpu_dm_mst_types.h   |  12 +-
>  3 files changed, 147 insertions(+), 118 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index 0db2a88cd4d7b..852a2100c6b38 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -6462,7 +6462,7 @@ static int
> dm_update_mst_vcpi_slots_for_dsc(struct drm_atomic_state *state,
>  	struct drm_connector_state *new_con_state;
>  	struct amdgpu_dm_connector *aconnector;
>  	struct dm_connector_state *dm_conn_state;
> -	int i, j;
> +	int i, j, ret;
>  	int vcpi, pbn_div, pbn, slot_num = 0;
> 
>  	for_each_new_connector_in_state(state, connector,
> new_con_state, i) { @@ -6509,8 +6509,11 @@ static int
> dm_update_mst_vcpi_slots_for_dsc(struct drm_atomic_state *state,
>  			dm_conn_state->pbn = pbn;
>  			dm_conn_state->vcpi_slots = slot_num;
> 
> -			drm_dp_mst_atomic_enable_dsc(state, aconnector-
> >port, dm_conn_state->pbn,
> -						     false);
> +			ret = drm_dp_mst_atomic_enable_dsc(state,
> aconnector->port,
> +							   dm_conn_state-
> >pbn, false);
> +			if (ret < 0)
> +				return ret;
> +
>  			continue;
>  		}
> 
> @@ -9523,10 +9526,9 @@ static int amdgpu_dm_atomic_check(struct
> drm_device *dev,
> 
>  #if defined(CONFIG_DRM_AMD_DC_DCN)
>  	if (dc_resource_is_dsc_encoding_supported(dc)) {
> -		if (!pre_validate_dsc(state, &dm_state, vars)) {
> -			ret = -EINVAL;
> +		ret = pre_validate_dsc(state, &dm_state, vars);
> +		if (ret != 0)
>  			goto fail;
> -		}
>  	}
>  #endif
> 
> @@ -9621,9 +9623,9 @@ static int amdgpu_dm_atomic_check(struct
> drm_device *dev,
>  		}
> 
>  #if defined(CONFIG_DRM_AMD_DC_DCN)
> -		if (!compute_mst_dsc_configs_for_state(state, dm_state-
> >context, vars)) {
> +		ret = compute_mst_dsc_configs_for_state(state, dm_state-
> >context, vars);
> +		if (ret) {
> 
> 	DRM_DEBUG_DRIVER("compute_mst_dsc_configs_for_state()
> failed\n");
> -			ret = -EINVAL;
>  			goto fail;
>  		}
> 
> diff --git
> a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> index 6ff96b4bdda5c..bba2e8aaa2c20 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> +++
> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> @@ -703,13 +703,13 @@ static int bpp_x16_from_pbn(struct
> dsc_mst_fairness_params param, int pbn)
>  	return dsc_config.bits_per_pixel;
>  }
> 
> -static bool increase_dsc_bpp(struct drm_atomic_state *state,
> -			     struct drm_dp_mst_topology_state *mst_state,
> -			     struct dc_link *dc_link,
> -			     struct dsc_mst_fairness_params *params,
> -			     struct dsc_mst_fairness_vars *vars,
> -			     int count,
> -			     int k)
> +static int increase_dsc_bpp(struct drm_atomic_state *state,
> +			    struct drm_dp_mst_topology_state *mst_state,
> +			    struct dc_link *dc_link,
> +			    struct dsc_mst_fairness_params *params,
> +			    struct dsc_mst_fairness_vars *vars,
> +			    int count,
> +			    int k)
>  {
>  	int i;
>  	bool bpp_increased[MAX_PIPES];
> @@ -719,6 +719,7 @@ static bool increase_dsc_bpp(struct
> drm_atomic_state *state,
>  	int remaining_to_increase = 0;
>  	int link_timeslots_used;
>  	int fair_pbn_alloc;
> +	int ret = 0;
> 
>  	for (i = 0; i < count; i++) {
>  		if (vars[i + k].dsc_enabled) {
> @@ -757,52 +758,60 @@ static bool increase_dsc_bpp(struct
> drm_atomic_state *state,
> 
>  		if (initial_slack[next_index] > fair_pbn_alloc) {
>  			vars[next_index].pbn += fair_pbn_alloc;
> -			if (drm_dp_atomic_find_time_slots(state,
> -
> params[next_index].port->mgr,
> -
> params[next_index].port,
> -
> vars[next_index].pbn) < 0)
> -				return false;
> -			if (!drm_dp_mst_atomic_check(state)) {
> +			ret = drm_dp_atomic_find_time_slots(state,
> +
> params[next_index].port->mgr,
> +
> params[next_index].port,
> +
> vars[next_index].pbn);
> +			if (ret < 0)
> +				return ret;
> +
> +			ret = drm_dp_mst_atomic_check(state);
> +			if (ret == 0) {
>  				vars[next_index].bpp_x16 =
> bpp_x16_from_pbn(params[next_index], vars[next_index].pbn);
>  			} else {
>  				vars[next_index].pbn -= fair_pbn_alloc;
> -				if (drm_dp_atomic_find_time_slots(state,
> -
> params[next_index].port->mgr,
> -
> params[next_index].port,
> -
> vars[next_index].pbn) < 0)
> -					return false;
> +				ret = drm_dp_atomic_find_time_slots(state,
> +
> params[next_index].port->mgr,
> +
> params[next_index].port,
> +
> vars[next_index].pbn);
> +				if (ret < 0)
> +					return ret;
>  			}
>  		} else {
>  			vars[next_index].pbn += initial_slack[next_index];
> -			if (drm_dp_atomic_find_time_slots(state,
> -
> params[next_index].port->mgr,
> -
> params[next_index].port,
> -
> vars[next_index].pbn) < 0)
> -				return false;
> -			if (!drm_dp_mst_atomic_check(state)) {
> +			ret = drm_dp_atomic_find_time_slots(state,
> +
> params[next_index].port->mgr,
> +
> params[next_index].port,
> +
> vars[next_index].pbn);
> +			if (ret < 0)
> +				return ret;
> +
> +			ret = drm_dp_mst_atomic_check(state);
> +			if (ret == 0) {
>  				vars[next_index].bpp_x16 =
> params[next_index].bw_range.max_target_bpp_x16;
>  			} else {
>  				vars[next_index].pbn -=
> initial_slack[next_index];
> -				if (drm_dp_atomic_find_time_slots(state,
> -
> params[next_index].port->mgr,
> -
> params[next_index].port,
> -
> vars[next_index].pbn) < 0)
> -					return false;
> +				ret = drm_dp_atomic_find_time_slots(state,
> +
> params[next_index].port->mgr,
> +
> params[next_index].port,
> +
> vars[next_index].pbn);
> +				if (ret < 0)
> +					return ret;
>  			}
>  		}
> 
>  		bpp_increased[next_index] = true;
>  		remaining_to_increase--;
>  	}
> -	return true;
> +	return 0;
>  }
> 
> -static bool try_disable_dsc(struct drm_atomic_state *state,
> -			    struct dc_link *dc_link,
> -			    struct dsc_mst_fairness_params *params,
> -			    struct dsc_mst_fairness_vars *vars,
> -			    int count,
> -			    int k)
> +static int try_disable_dsc(struct drm_atomic_state *state,
> +			   struct dc_link *dc_link,
> +			   struct dsc_mst_fairness_params *params,
> +			   struct dsc_mst_fairness_vars *vars,
> +			   int count,
> +			   int k)
>  {
>  	int i;
>  	bool tried[MAX_PIPES];
> @@ -810,6 +819,7 @@ static bool try_disable_dsc(struct drm_atomic_state
> *state,
>  	int max_kbps_increase;
>  	int next_index;
>  	int remaining_to_try = 0;
> +	int ret;
> 
>  	for (i = 0; i < count; i++) {
>  		if (vars[i + k].dsc_enabled
> @@ -840,49 +850,52 @@ static bool try_disable_dsc(struct
> drm_atomic_state *state,
>  			break;
> 
>  		vars[next_index].pbn =
> kbps_to_peak_pbn(params[next_index].bw_range.stream_kbps);
> -		if (drm_dp_atomic_find_time_slots(state,
> -						  params[next_index].port-
> >mgr,
> -						  params[next_index].port,
> -						  vars[next_index].pbn) < 0)
> -			return false;
> +		ret = drm_dp_atomic_find_time_slots(state,
> +						    params[next_index].port-
> >mgr,
> +						    params[next_index].port,
> +						    vars[next_index].pbn);
> +		if (ret < 0)
> +			return ret;
> 
> -		if (!drm_dp_mst_atomic_check(state)) {
> +		ret = drm_dp_mst_atomic_check(state);
> +		if (ret == 0) {
>  			vars[next_index].dsc_enabled = false;
>  			vars[next_index].bpp_x16 = 0;
>  		} else {
>  			vars[next_index].pbn =
> kbps_to_peak_pbn(params[next_index].bw_range.max_kbps);
> -			if (drm_dp_atomic_find_time_slots(state,
> -
> params[next_index].port->mgr,
> -
> params[next_index].port,
> -
> vars[next_index].pbn) < 0)
> -				return false;
> +			ret = drm_dp_atomic_find_time_slots(state,
> +
> params[next_index].port->mgr,
> +
> params[next_index].port,
> +
> vars[next_index].pbn);
> +			if (ret < 0)
> +				return ret;
>  		}
> 
>  		tried[next_index] = true;
>  		remaining_to_try--;
>  	}
> -	return true;
> +	return 0;
>  }
> 
> -static bool compute_mst_dsc_configs_for_link(struct drm_atomic_state
> *state,
> -					     struct dc_state *dc_state,
> -					     struct dc_link *dc_link,
> -					     struct dsc_mst_fairness_vars *vars,
> -					     struct drm_dp_mst_topology_mgr
> *mgr,
> -					     int *link_vars_start_index)
> +static int compute_mst_dsc_configs_for_link(struct drm_atomic_state
> *state,
> +					    struct dc_state *dc_state,
> +					    struct dc_link *dc_link,
> +					    struct dsc_mst_fairness_vars *vars,
> +					    struct drm_dp_mst_topology_mgr
> *mgr,
> +					    int *link_vars_start_index)
>  {
>  	struct dc_stream_state *stream;
>  	struct dsc_mst_fairness_params params[MAX_PIPES];
>  	struct amdgpu_dm_connector *aconnector;
>  	struct drm_dp_mst_topology_state *mst_state =
> drm_atomic_get_mst_topology_state(state, mgr);
>  	int count = 0;
> -	int i, k;
> +	int i, k, ret;
>  	bool debugfs_overwrite = false;
> 
>  	memset(params, 0, sizeof(params));
> 
>  	if (IS_ERR(mst_state))
> -		return false;
> +		return PTR_ERR(mst_state);
> 
>  	mst_state->pbn_div = dm_mst_get_pbn_divider(dc_link);  #if
> defined(CONFIG_DRM_AMD_DC_DCN) @@ -933,7 +946,7 @@ static bool
> compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,
> 
>  	if (count == 0) {
>  		ASSERT(0);
> -		return true;
> +		return 0;
>  	}
> 
>  	/* k is start index of vars for current phy link used by mst hub */ @@
> -947,13 +960,17 @@ static bool compute_mst_dsc_configs_for_link(struct
> drm_atomic_state *state,
>  		vars[i + k].pbn =
> kbps_to_peak_pbn(params[i].bw_range.stream_kbps);
>  		vars[i + k].dsc_enabled = false;
>  		vars[i + k].bpp_x16 = 0;
> -		if (drm_dp_atomic_find_time_slots(state, params[i].port-
> >mgr, params[i].port,
> -						  vars[i + k].pbn) < 0)
> -			return false;
> +		ret = drm_dp_atomic_find_time_slots(state, params[i].port-
> >mgr, params[i].port,
> +						    vars[i + k].pbn);
> +		if (ret < 0)
> +			return ret;
>  	}
> -	if (!drm_dp_mst_atomic_check(state) && !debugfs_overwrite) {
> +	ret = drm_dp_mst_atomic_check(state);
> +	if (ret == 0 && !debugfs_overwrite) {
>  		set_dsc_configs_from_fairness_vars(params, vars, count, k);
> -		return true;
> +		return 0;
> +	} else if (ret != -ENOSPC) {
> +		return ret;
>  	}
> 
>  	/* Try max compression */
> @@ -962,31 +979,36 @@ static bool
> compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,
>  			vars[i + k].pbn =
> kbps_to_peak_pbn(params[i].bw_range.min_kbps);
>  			vars[i + k].dsc_enabled = true;
>  			vars[i + k].bpp_x16 =
> params[i].bw_range.min_target_bpp_x16;
> -			if (drm_dp_atomic_find_time_slots(state,
> params[i].port->mgr,
> -							  params[i].port, vars[i
> + k].pbn) < 0)
> -				return false;
> +			ret = drm_dp_atomic_find_time_slots(state,
> params[i].port->mgr,
> +							    params[i].port,
> vars[i + k].pbn);
> +			if (ret < 0)
> +				return ret;
>  		} else {
>  			vars[i + k].pbn =
> kbps_to_peak_pbn(params[i].bw_range.stream_kbps);
>  			vars[i + k].dsc_enabled = false;
>  			vars[i + k].bpp_x16 = 0;
> -			if (drm_dp_atomic_find_time_slots(state,
> params[i].port->mgr,
> -							  params[i].port, vars[i
> + k].pbn) < 0)
> -				return false;
> +			ret = drm_dp_atomic_find_time_slots(state,
> params[i].port->mgr,
> +							    params[i].port,
> vars[i + k].pbn);
> +			if (ret < 0)
> +				return ret;
>  		}
>  	}
> -	if (drm_dp_mst_atomic_check(state))
> -		return false;
> +	ret = drm_dp_mst_atomic_check(state);
> +	if (ret != 0)
> +		return ret;
> 
>  	/* Optimize degree of compression */
> -	if (!increase_dsc_bpp(state, mst_state, dc_link, params, vars, count,
> k))
> -		return false;
> +	ret = increase_dsc_bpp(state, mst_state, dc_link, params, vars,
> count, k);
> +	if (ret < 0)
> +		return ret;
> 
> -	if (!try_disable_dsc(state, dc_link, params, vars, count, k))
> -		return false;
> +	ret = try_disable_dsc(state, dc_link, params, vars, count, k);
> +	if (ret < 0)
> +		return ret;
> 
>  	set_dsc_configs_from_fairness_vars(params, vars, count, k);
> 
> -	return true;
> +	return 0;
>  }
> 
>  static bool is_dsc_need_re_compute(
> @@ -1087,15 +1109,16 @@ static bool is_dsc_need_re_compute(
>  	return is_dsc_need_re_compute;
>  }
> 
> -bool compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> -				       struct dc_state *dc_state,
> -				       struct dsc_mst_fairness_vars *vars)
> +int compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> +				      struct dc_state *dc_state,
> +				      struct dsc_mst_fairness_vars *vars)
>  {
>  	int i, j;
>  	struct dc_stream_state *stream;
>  	bool computed_streams[MAX_PIPES];
>  	struct amdgpu_dm_connector *aconnector;
>  	int link_vars_start_index = 0;
> +	int ret = 0;
> 
>  	for (i = 0; i < dc_state->stream_count; i++)
>  		computed_streams[i] = false;
> @@ -1118,17 +1141,19 @@ bool compute_mst_dsc_configs_for_state(struct
> drm_atomic_state *state,
>  			continue;
> 
>  		if (dcn20_remove_stream_from_ctx(stream->ctx->dc,
> dc_state, stream) != DC_OK)
> -			return false;
> +			return -EINVAL;
> 
>  		if (!is_dsc_need_re_compute(state, dc_state, stream->link))
>  			continue;
> 
>  		mutex_lock(&aconnector->mst_mgr.lock);
> -		if (!compute_mst_dsc_configs_for_link(state, dc_state,
> stream->link, vars,
> -						      &aconnector->mst_mgr,
> -						      &link_vars_start_index)) {
> +
> +		ret = compute_mst_dsc_configs_for_link(state, dc_state,
> stream->link, vars,
> +						       &aconnector->mst_mgr,
> +						       &link_vars_start_index);
> +		if (ret != 0) {
>  			mutex_unlock(&aconnector->mst_mgr.lock);
> -			return false;
> +			return ret;
>  		}
>  		mutex_unlock(&aconnector->mst_mgr.lock);
> 
> @@ -1143,22 +1168,22 @@ bool compute_mst_dsc_configs_for_state(struct
> drm_atomic_state *state,
> 
>  		if (stream->timing.flags.DSC == 1)
>  			if (dc_stream_add_dsc_to_resource(stream->ctx-
> >dc, dc_state, stream) != DC_OK)
> -				return false;
> +				return -EINVAL;
>  	}
> 
> -	return true;
> +	return ret;
>  }
> 
> -static bool
> -	pre_compute_mst_dsc_configs_for_state(struct drm_atomic_state
> *state,
> -					      struct dc_state *dc_state,
> -					      struct dsc_mst_fairness_vars
> *vars)
> +static int pre_compute_mst_dsc_configs_for_state(struct
> drm_atomic_state *state,
> +						 struct dc_state *dc_state,
> +						 struct dsc_mst_fairness_vars
> *vars)
>  {
>  	int i, j;
>  	struct dc_stream_state *stream;
>  	bool computed_streams[MAX_PIPES];
>  	struct amdgpu_dm_connector *aconnector;
>  	int link_vars_start_index = 0;
> +	int ret;
> 
>  	for (i = 0; i < dc_state->stream_count; i++)
>  		computed_streams[i] = false;
> @@ -1184,11 +1209,12 @@ static bool
>  			continue;
> 
>  		mutex_lock(&aconnector->mst_mgr.lock);
> -		if (!compute_mst_dsc_configs_for_link(state, dc_state,
> stream->link, vars,
> -						      &aconnector->mst_mgr,
> -						      &link_vars_start_index)) {
> +		ret = compute_mst_dsc_configs_for_link(state, dc_state,
> stream->link, vars,
> +						       &aconnector->mst_mgr,
> +						       &link_vars_start_index);
> +		if (ret != 0) {
>  			mutex_unlock(&aconnector->mst_mgr.lock);
> -			return false;
> +			return ret;
>  		}
>  		mutex_unlock(&aconnector->mst_mgr.lock);
> 
> @@ -1198,7 +1224,7 @@ static bool
>  		}
>  	}
> 
> -	return true;
> +	return ret;
>  }
> 
>  static int find_crtc_index_in_state_by_stream(struct drm_atomic_state
> *state, @@ -1253,9 +1279,9 @@ static bool
> is_dsc_precompute_needed(struct drm_atomic_state *state)
>  	return ret;
>  }
> 
> -bool pre_validate_dsc(struct drm_atomic_state *state,
> -		      struct dm_atomic_state **dm_state_ptr,
> -		      struct dsc_mst_fairness_vars *vars)
> +int pre_validate_dsc(struct drm_atomic_state *state,
> +		     struct dm_atomic_state **dm_state_ptr,
> +		     struct dsc_mst_fairness_vars *vars)
>  {
>  	int i;
>  	struct dm_atomic_state *dm_state;
> @@ -1264,11 +1290,12 @@ bool pre_validate_dsc(struct drm_atomic_state
> *state,
> 
>  	if (!is_dsc_precompute_needed(state)) {
>  		DRM_INFO_ONCE("DSC precompute is not needed.\n");
> -		return true;
> +		return 0;
>  	}
> -	if (dm_atomic_get_state(state, dm_state_ptr)) {
> +	ret = dm_atomic_get_state(state, dm_state_ptr);
> +	if (ret != 0) {
>  		DRM_INFO_ONCE("dm_atomic_get_state() failed\n");
> -		return false;
> +		return ret;
>  	}
>  	dm_state = *dm_state_ptr;
> 
> @@ -1280,7 +1307,7 @@ bool pre_validate_dsc(struct drm_atomic_state
> *state,
> 
>  	local_dc_state = kmemdup(dm_state->context, sizeof(struct
> dc_state), GFP_KERNEL);
>  	if (!local_dc_state)
> -		return false;
> +		return -ENOMEM;
> 
>  	for (i = 0; i < local_dc_state->stream_count; i++) {
>  		struct dc_stream_state *stream = dm_state->context-
> >streams[i]; @@ -1316,9 +1343,9 @@ bool pre_validate_dsc(struct
> drm_atomic_state *state,
>  	if (ret != 0)
>  		goto clean_exit;
> 
> -	if (!pre_compute_mst_dsc_configs_for_state(state, local_dc_state,
> vars)) {
> +	ret = pre_compute_mst_dsc_configs_for_state(state, local_dc_state,
> vars);
> +	if (ret != 0) {
> 
> 	DRM_INFO_ONCE("pre_compute_mst_dsc_configs_for_state()
> failed\n");
> -		ret = -EINVAL;
>  		goto clean_exit;
>  	}
> 
> @@ -1349,7 +1376,7 @@ bool pre_validate_dsc(struct drm_atomic_state
> *state,
> 
>  	kfree(local_dc_state);
> 
> -	return (ret == 0);
> +	return ret;
>  }
> 
>  static unsigned int kbps_from_pbn(unsigned int pbn) diff --git
> a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> index b92a7c5671aa2..97fd70df531bf 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> +++
> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> @@ -53,15 +53,15 @@ struct dsc_mst_fairness_vars {
>  	struct amdgpu_dm_connector *aconnector;  };
> 
> -bool compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> -				       struct dc_state *dc_state,
> -				       struct dsc_mst_fairness_vars *vars);
> +int compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> +				      struct dc_state *dc_state,
> +				      struct dsc_mst_fairness_vars *vars);
> 
>  bool needs_dsc_aux_workaround(struct dc_link *link);
> 
> -bool pre_validate_dsc(struct drm_atomic_state *state,
> -		      struct dm_atomic_state **dm_state_ptr,
> -		      struct dsc_mst_fairness_vars *vars);
> +int pre_validate_dsc(struct drm_atomic_state *state,
> +		     struct dm_atomic_state **dm_state_ptr,
> +		     struct dsc_mst_fairness_vars *vars);
> 
>  enum dc_status dm_dp_mst_is_port_support_mode(
>  	struct amdgpu_dm_connector *aconnector,
> --
> 2.37.3
  

On Wed, 2022-11-16 at 04:39 +0000, Lin, Wayne wrote:
> [Public]
> 
> All the patch set looks good to me. Feel free to add:
> Reviewed-by: Wayne Lin <Wayne.Lin@amd.com>
> 
> Again, thank you Lyude for helping on this!!!

No problem! I was the one who introduced the bug anyway :P, I'm just glad we
were able to fix this on time.

Harry, Alex - feel free to merge this on whatever branch you want (I'm fine
with the mst-helper bits going through amd's branch, especially since AMD is
the only driver using the dsc stuff right now)

> 
> Regards,
> Wayne
> > -----Original Message-----
> > From: Lyude Paul <lyude@redhat.com>
> > Sent: Tuesday, November 15, 2022 6:18 AM
> > To: amd-gfx@lists.freedesktop.org
> > Cc: Wentland, Harry <Harry.Wentland@amd.com>; stable@vger.kernel.org;
> > Li, Sun peng (Leo) <Sunpeng.Li@amd.com>; Siqueira, Rodrigo
> > <Rodrigo.Siqueira@amd.com>; Deucher, Alexander
> > <Alexander.Deucher@amd.com>; Koenig, Christian
> > <Christian.Koenig@amd.com>; Pan, Xinhui <Xinhui.Pan@amd.com>; David
> > Airlie <airlied@gmail.com>; Daniel Vetter <daniel@ffwll.ch>; Kazlauskas,
> > Nicholas <Nicholas.Kazlauskas@amd.com>; Pillai, Aurabindo
> > <Aurabindo.Pillai@amd.com>; Li, Roman <Roman.Li@amd.com>; Zuo, Jerry
> > <Jerry.Zuo@amd.com>; Wu, Hersen <hersenxs.wu@amd.com>; Lin, Wayne
> > <Wayne.Lin@amd.com>; Thomas Zimmermann <tzimmermann@suse.de>;
> > Mahfooz, Hamza <Hamza.Mahfooz@amd.com>; Hung, Alex
> > <Alex.Hung@amd.com>; Mikita Lipski <mikita.lipski@amd.com>; Liu,
> > Wenjing <Wenjing.Liu@amd.com>; Francis, David
> > <David.Francis@amd.com>; open list:DRM DRIVERS <dri-
> > devel@lists.freedesktop.org>; open list <linux-kernel@vger.kernel.org>
> > Subject: [PATCH v2 1/4] drm/amdgpu/mst: Stop ignoring error codes and
> > deadlocking
> > 
> > It appears that amdgpu makes the mistake of completely ignoring the return
> > values from the DP MST helpers, and instead just returns a simple true/false.
> > In this case, it seems to have come back to bite us because as a result of
> > simply returning false from compute_mst_dsc_configs_for_state(), amdgpu
> > had no way of telling when a deadlock happened from these helpers. This
> > could definitely result in some kernel splats.
> > 
> > V2:
> > * Address Wayne's comments (fix another bunch of spots where we weren't
> >   passing down return codes)
> > 
> > Signed-off-by: Lyude Paul <lyude@redhat.com>
> > Fixes: 8c20a1ed9b4f ("drm/amd/display: MST DSC compute fair share")
> > Cc: Harry Wentland <harry.wentland@amd.com>
> > Cc: <stable@vger.kernel.org> # v5.6+
> > ---
> >  .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |  18 +-
> >  .../display/amdgpu_dm/amdgpu_dm_mst_types.c   | 235 ++++++++++------
> > --
> >  .../display/amdgpu_dm/amdgpu_dm_mst_types.h   |  12 +-
> >  3 files changed, 147 insertions(+), 118 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > index 0db2a88cd4d7b..852a2100c6b38 100644
> > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > @@ -6462,7 +6462,7 @@ static int
> > dm_update_mst_vcpi_slots_for_dsc(struct drm_atomic_state *state,
> >  	struct drm_connector_state *new_con_state;
> >  	struct amdgpu_dm_connector *aconnector;
> >  	struct dm_connector_state *dm_conn_state;
> > -	int i, j;
> > +	int i, j, ret;
> >  	int vcpi, pbn_div, pbn, slot_num = 0;
> > 
> >  	for_each_new_connector_in_state(state, connector,
> > new_con_state, i) { @@ -6509,8 +6509,11 @@ static int
> > dm_update_mst_vcpi_slots_for_dsc(struct drm_atomic_state *state,
> >  			dm_conn_state->pbn = pbn;
> >  			dm_conn_state->vcpi_slots = slot_num;
> > 
> > -			drm_dp_mst_atomic_enable_dsc(state, aconnector-
> > > port, dm_conn_state->pbn,
> > -						     false);
> > +			ret = drm_dp_mst_atomic_enable_dsc(state,
> > aconnector->port,
> > +							   dm_conn_state-
> > > pbn, false);
> > +			if (ret < 0)
> > +				return ret;
> > +
> >  			continue;
> >  		}
> > 
> > @@ -9523,10 +9526,9 @@ static int amdgpu_dm_atomic_check(struct
> > drm_device *dev,
> > 
> >  #if defined(CONFIG_DRM_AMD_DC_DCN)
> >  	if (dc_resource_is_dsc_encoding_supported(dc)) {
> > -		if (!pre_validate_dsc(state, &dm_state, vars)) {
> > -			ret = -EINVAL;
> > +		ret = pre_validate_dsc(state, &dm_state, vars);
> > +		if (ret != 0)
> >  			goto fail;
> > -		}
> >  	}
> >  #endif
> > 
> > @@ -9621,9 +9623,9 @@ static int amdgpu_dm_atomic_check(struct
> > drm_device *dev,
> >  		}
> > 
> >  #if defined(CONFIG_DRM_AMD_DC_DCN)
> > -		if (!compute_mst_dsc_configs_for_state(state, dm_state-
> > > context, vars)) {
> > +		ret = compute_mst_dsc_configs_for_state(state, dm_state-
> > > context, vars);
> > +		if (ret) {
> > 
> > 	DRM_DEBUG_DRIVER("compute_mst_dsc_configs_for_state()
> > failed\n");
> > -			ret = -EINVAL;
> >  			goto fail;
> >  		}
> > 
> > diff --git
> > a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > index 6ff96b4bdda5c..bba2e8aaa2c20 100644
> > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > +++
> > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > @@ -703,13 +703,13 @@ static int bpp_x16_from_pbn(struct
> > dsc_mst_fairness_params param, int pbn)
> >  	return dsc_config.bits_per_pixel;
> >  }
> > 
> > -static bool increase_dsc_bpp(struct drm_atomic_state *state,
> > -			     struct drm_dp_mst_topology_state *mst_state,
> > -			     struct dc_link *dc_link,
> > -			     struct dsc_mst_fairness_params *params,
> > -			     struct dsc_mst_fairness_vars *vars,
> > -			     int count,
> > -			     int k)
> > +static int increase_dsc_bpp(struct drm_atomic_state *state,
> > +			    struct drm_dp_mst_topology_state *mst_state,
> > +			    struct dc_link *dc_link,
> > +			    struct dsc_mst_fairness_params *params,
> > +			    struct dsc_mst_fairness_vars *vars,
> > +			    int count,
> > +			    int k)
> >  {
> >  	int i;
> >  	bool bpp_increased[MAX_PIPES];
> > @@ -719,6 +719,7 @@ static bool increase_dsc_bpp(struct
> > drm_atomic_state *state,
> >  	int remaining_to_increase = 0;
> >  	int link_timeslots_used;
> >  	int fair_pbn_alloc;
> > +	int ret = 0;
> > 
> >  	for (i = 0; i < count; i++) {
> >  		if (vars[i + k].dsc_enabled) {
> > @@ -757,52 +758,60 @@ static bool increase_dsc_bpp(struct
> > drm_atomic_state *state,
> > 
> >  		if (initial_slack[next_index] > fair_pbn_alloc) {
> >  			vars[next_index].pbn += fair_pbn_alloc;
> > -			if (drm_dp_atomic_find_time_slots(state,
> > -
> > params[next_index].port->mgr,
> > -
> > params[next_index].port,
> > -
> > vars[next_index].pbn) < 0)
> > -				return false;
> > -			if (!drm_dp_mst_atomic_check(state)) {
> > +			ret = drm_dp_atomic_find_time_slots(state,
> > +
> > params[next_index].port->mgr,
> > +
> > params[next_index].port,
> > +
> > vars[next_index].pbn);
> > +			if (ret < 0)
> > +				return ret;
> > +
> > +			ret = drm_dp_mst_atomic_check(state);
> > +			if (ret == 0) {
> >  				vars[next_index].bpp_x16 =
> > bpp_x16_from_pbn(params[next_index], vars[next_index].pbn);
> >  			} else {
> >  				vars[next_index].pbn -= fair_pbn_alloc;
> > -				if (drm_dp_atomic_find_time_slots(state,
> > -
> > params[next_index].port->mgr,
> > -
> > params[next_index].port,
> > -
> > vars[next_index].pbn) < 0)
> > -					return false;
> > +				ret = drm_dp_atomic_find_time_slots(state,
> > +
> > params[next_index].port->mgr,
> > +
> > params[next_index].port,
> > +
> > vars[next_index].pbn);
> > +				if (ret < 0)
> > +					return ret;
> >  			}
> >  		} else {
> >  			vars[next_index].pbn += initial_slack[next_index];
> > -			if (drm_dp_atomic_find_time_slots(state,
> > -
> > params[next_index].port->mgr,
> > -
> > params[next_index].port,
> > -
> > vars[next_index].pbn) < 0)
> > -				return false;
> > -			if (!drm_dp_mst_atomic_check(state)) {
> > +			ret = drm_dp_atomic_find_time_slots(state,
> > +
> > params[next_index].port->mgr,
> > +
> > params[next_index].port,
> > +
> > vars[next_index].pbn);
> > +			if (ret < 0)
> > +				return ret;
> > +
> > +			ret = drm_dp_mst_atomic_check(state);
> > +			if (ret == 0) {
> >  				vars[next_index].bpp_x16 =
> > params[next_index].bw_range.max_target_bpp_x16;
> >  			} else {
> >  				vars[next_index].pbn -=
> > initial_slack[next_index];
> > -				if (drm_dp_atomic_find_time_slots(state,
> > -
> > params[next_index].port->mgr,
> > -
> > params[next_index].port,
> > -
> > vars[next_index].pbn) < 0)
> > -					return false;
> > +				ret = drm_dp_atomic_find_time_slots(state,
> > +
> > params[next_index].port->mgr,
> > +
> > params[next_index].port,
> > +
> > vars[next_index].pbn);
> > +				if (ret < 0)
> > +					return ret;
> >  			}
> >  		}
> > 
> >  		bpp_increased[next_index] = true;
> >  		remaining_to_increase--;
> >  	}
> > -	return true;
> > +	return 0;
> >  }
> > 
> > -static bool try_disable_dsc(struct drm_atomic_state *state,
> > -			    struct dc_link *dc_link,
> > -			    struct dsc_mst_fairness_params *params,
> > -			    struct dsc_mst_fairness_vars *vars,
> > -			    int count,
> > -			    int k)
> > +static int try_disable_dsc(struct drm_atomic_state *state,
> > +			   struct dc_link *dc_link,
> > +			   struct dsc_mst_fairness_params *params,
> > +			   struct dsc_mst_fairness_vars *vars,
> > +			   int count,
> > +			   int k)
> >  {
> >  	int i;
> >  	bool tried[MAX_PIPES];
> > @@ -810,6 +819,7 @@ static bool try_disable_dsc(struct drm_atomic_state
> > *state,
> >  	int max_kbps_increase;
> >  	int next_index;
> >  	int remaining_to_try = 0;
> > +	int ret;
> > 
> >  	for (i = 0; i < count; i++) {
> >  		if (vars[i + k].dsc_enabled
> > @@ -840,49 +850,52 @@ static bool try_disable_dsc(struct
> > drm_atomic_state *state,
> >  			break;
> > 
> >  		vars[next_index].pbn =
> > kbps_to_peak_pbn(params[next_index].bw_range.stream_kbps);
> > -		if (drm_dp_atomic_find_time_slots(state,
> > -						  params[next_index].port-
> > > mgr,
> > -						  params[next_index].port,
> > -						  vars[next_index].pbn) < 0)
> > -			return false;
> > +		ret = drm_dp_atomic_find_time_slots(state,
> > +						    params[next_index].port-
> > > mgr,
> > +						    params[next_index].port,
> > +						    vars[next_index].pbn);
> > +		if (ret < 0)
> > +			return ret;
> > 
> > -		if (!drm_dp_mst_atomic_check(state)) {
> > +		ret = drm_dp_mst_atomic_check(state);
> > +		if (ret == 0) {
> >  			vars[next_index].dsc_enabled = false;
> >  			vars[next_index].bpp_x16 = 0;
> >  		} else {
> >  			vars[next_index].pbn =
> > kbps_to_peak_pbn(params[next_index].bw_range.max_kbps);
> > -			if (drm_dp_atomic_find_time_slots(state,
> > -
> > params[next_index].port->mgr,
> > -
> > params[next_index].port,
> > -
> > vars[next_index].pbn) < 0)
> > -				return false;
> > +			ret = drm_dp_atomic_find_time_slots(state,
> > +
> > params[next_index].port->mgr,
> > +
> > params[next_index].port,
> > +
> > vars[next_index].pbn);
> > +			if (ret < 0)
> > +				return ret;
> >  		}
> > 
> >  		tried[next_index] = true;
> >  		remaining_to_try--;
> >  	}
> > -	return true;
> > +	return 0;
> >  }
> > 
> > -static bool compute_mst_dsc_configs_for_link(struct drm_atomic_state
> > *state,
> > -					     struct dc_state *dc_state,
> > -					     struct dc_link *dc_link,
> > -					     struct dsc_mst_fairness_vars *vars,
> > -					     struct drm_dp_mst_topology_mgr
> > *mgr,
> > -					     int *link_vars_start_index)
> > +static int compute_mst_dsc_configs_for_link(struct drm_atomic_state
> > *state,
> > +					    struct dc_state *dc_state,
> > +					    struct dc_link *dc_link,
> > +					    struct dsc_mst_fairness_vars *vars,
> > +					    struct drm_dp_mst_topology_mgr
> > *mgr,
> > +					    int *link_vars_start_index)
> >  {
> >  	struct dc_stream_state *stream;
> >  	struct dsc_mst_fairness_params params[MAX_PIPES];
> >  	struct amdgpu_dm_connector *aconnector;
> >  	struct drm_dp_mst_topology_state *mst_state =
> > drm_atomic_get_mst_topology_state(state, mgr);
> >  	int count = 0;
> > -	int i, k;
> > +	int i, k, ret;
> >  	bool debugfs_overwrite = false;
> > 
> >  	memset(params, 0, sizeof(params));
> > 
> >  	if (IS_ERR(mst_state))
> > -		return false;
> > +		return PTR_ERR(mst_state);
> > 
> >  	mst_state->pbn_div = dm_mst_get_pbn_divider(dc_link);  #if
> > defined(CONFIG_DRM_AMD_DC_DCN) @@ -933,7 +946,7 @@ static bool
> > compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,
> > 
> >  	if (count == 0) {
> >  		ASSERT(0);
> > -		return true;
> > +		return 0;
> >  	}
> > 
> >  	/* k is start index of vars for current phy link used by mst hub */ @@
> > -947,13 +960,17 @@ static bool compute_mst_dsc_configs_for_link(struct
> > drm_atomic_state *state,
> >  		vars[i + k].pbn =
> > kbps_to_peak_pbn(params[i].bw_range.stream_kbps);
> >  		vars[i + k].dsc_enabled = false;
> >  		vars[i + k].bpp_x16 = 0;
> > -		if (drm_dp_atomic_find_time_slots(state, params[i].port-
> > > mgr, params[i].port,
> > -						  vars[i + k].pbn) < 0)
> > -			return false;
> > +		ret = drm_dp_atomic_find_time_slots(state, params[i].port-
> > > mgr, params[i].port,
> > +						    vars[i + k].pbn);
> > +		if (ret < 0)
> > +			return ret;
> >  	}
> > -	if (!drm_dp_mst_atomic_check(state) && !debugfs_overwrite) {
> > +	ret = drm_dp_mst_atomic_check(state);
> > +	if (ret == 0 && !debugfs_overwrite) {
> >  		set_dsc_configs_from_fairness_vars(params, vars, count, k);
> > -		return true;
> > +		return 0;
> > +	} else if (ret != -ENOSPC) {
> > +		return ret;
> >  	}
> > 
> >  	/* Try max compression */
> > @@ -962,31 +979,36 @@ static bool
> > compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,
> >  			vars[i + k].pbn =
> > kbps_to_peak_pbn(params[i].bw_range.min_kbps);
> >  			vars[i + k].dsc_enabled = true;
> >  			vars[i + k].bpp_x16 =
> > params[i].bw_range.min_target_bpp_x16;
> > -			if (drm_dp_atomic_find_time_slots(state,
> > params[i].port->mgr,
> > -							  params[i].port, vars[i
> > + k].pbn) < 0)
> > -				return false;
> > +			ret = drm_dp_atomic_find_time_slots(state,
> > params[i].port->mgr,
> > +							    params[i].port,
> > vars[i + k].pbn);
> > +			if (ret < 0)
> > +				return ret;
> >  		} else {
> >  			vars[i + k].pbn =
> > kbps_to_peak_pbn(params[i].bw_range.stream_kbps);
> >  			vars[i + k].dsc_enabled = false;
> >  			vars[i + k].bpp_x16 = 0;
> > -			if (drm_dp_atomic_find_time_slots(state,
> > params[i].port->mgr,
> > -							  params[i].port, vars[i
> > + k].pbn) < 0)
> > -				return false;
> > +			ret = drm_dp_atomic_find_time_slots(state,
> > params[i].port->mgr,
> > +							    params[i].port,
> > vars[i + k].pbn);
> > +			if (ret < 0)
> > +				return ret;
> >  		}
> >  	}
> > -	if (drm_dp_mst_atomic_check(state))
> > -		return false;
> > +	ret = drm_dp_mst_atomic_check(state);
> > +	if (ret != 0)
> > +		return ret;
> > 
> >  	/* Optimize degree of compression */
> > -	if (!increase_dsc_bpp(state, mst_state, dc_link, params, vars, count,
> > k))
> > -		return false;
> > +	ret = increase_dsc_bpp(state, mst_state, dc_link, params, vars,
> > count, k);
> > +	if (ret < 0)
> > +		return ret;
> > 
> > -	if (!try_disable_dsc(state, dc_link, params, vars, count, k))
> > -		return false;
> > +	ret = try_disable_dsc(state, dc_link, params, vars, count, k);
> > +	if (ret < 0)
> > +		return ret;
> > 
> >  	set_dsc_configs_from_fairness_vars(params, vars, count, k);
> > 
> > -	return true;
> > +	return 0;
> >  }
> > 
> >  static bool is_dsc_need_re_compute(
> > @@ -1087,15 +1109,16 @@ static bool is_dsc_need_re_compute(
> >  	return is_dsc_need_re_compute;
> >  }
> > 
> > -bool compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> > -				       struct dc_state *dc_state,
> > -				       struct dsc_mst_fairness_vars *vars)
> > +int compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> > +				      struct dc_state *dc_state,
> > +				      struct dsc_mst_fairness_vars *vars)
> >  {
> >  	int i, j;
> >  	struct dc_stream_state *stream;
> >  	bool computed_streams[MAX_PIPES];
> >  	struct amdgpu_dm_connector *aconnector;
> >  	int link_vars_start_index = 0;
> > +	int ret = 0;
> > 
> >  	for (i = 0; i < dc_state->stream_count; i++)
> >  		computed_streams[i] = false;
> > @@ -1118,17 +1141,19 @@ bool compute_mst_dsc_configs_for_state(struct
> > drm_atomic_state *state,
> >  			continue;
> > 
> >  		if (dcn20_remove_stream_from_ctx(stream->ctx->dc,
> > dc_state, stream) != DC_OK)
> > -			return false;
> > +			return -EINVAL;
> > 
> >  		if (!is_dsc_need_re_compute(state, dc_state, stream->link))
> >  			continue;
> > 
> >  		mutex_lock(&aconnector->mst_mgr.lock);
> > -		if (!compute_mst_dsc_configs_for_link(state, dc_state,
> > stream->link, vars,
> > -						      &aconnector->mst_mgr,
> > -						      &link_vars_start_index)) {
> > +
> > +		ret = compute_mst_dsc_configs_for_link(state, dc_state,
> > stream->link, vars,
> > +						       &aconnector->mst_mgr,
> > +						       &link_vars_start_index);
> > +		if (ret != 0) {
> >  			mutex_unlock(&aconnector->mst_mgr.lock);
> > -			return false;
> > +			return ret;
> >  		}
> >  		mutex_unlock(&aconnector->mst_mgr.lock);
> > 
> > @@ -1143,22 +1168,22 @@ bool compute_mst_dsc_configs_for_state(struct
> > drm_atomic_state *state,
> > 
> >  		if (stream->timing.flags.DSC == 1)
> >  			if (dc_stream_add_dsc_to_resource(stream->ctx-
> > > dc, dc_state, stream) != DC_OK)
> > -				return false;
> > +				return -EINVAL;
> >  	}
> > 
> > -	return true;
> > +	return ret;
> >  }
> > 
> > -static bool
> > -	pre_compute_mst_dsc_configs_for_state(struct drm_atomic_state
> > *state,
> > -					      struct dc_state *dc_state,
> > -					      struct dsc_mst_fairness_vars
> > *vars)
> > +static int pre_compute_mst_dsc_configs_for_state(struct
> > drm_atomic_state *state,
> > +						 struct dc_state *dc_state,
> > +						 struct dsc_mst_fairness_vars
> > *vars)
> >  {
> >  	int i, j;
> >  	struct dc_stream_state *stream;
> >  	bool computed_streams[MAX_PIPES];
> >  	struct amdgpu_dm_connector *aconnector;
> >  	int link_vars_start_index = 0;
> > +	int ret;
> > 
> >  	for (i = 0; i < dc_state->stream_count; i++)
> >  		computed_streams[i] = false;
> > @@ -1184,11 +1209,12 @@ static bool
> >  			continue;
> > 
> >  		mutex_lock(&aconnector->mst_mgr.lock);
> > -		if (!compute_mst_dsc_configs_for_link(state, dc_state,
> > stream->link, vars,
> > -						      &aconnector->mst_mgr,
> > -						      &link_vars_start_index)) {
> > +		ret = compute_mst_dsc_configs_for_link(state, dc_state,
> > stream->link, vars,
> > +						       &aconnector->mst_mgr,
> > +						       &link_vars_start_index);
> > +		if (ret != 0) {
> >  			mutex_unlock(&aconnector->mst_mgr.lock);
> > -			return false;
> > +			return ret;
> >  		}
> >  		mutex_unlock(&aconnector->mst_mgr.lock);
> > 
> > @@ -1198,7 +1224,7 @@ static bool
> >  		}
> >  	}
> > 
> > -	return true;
> > +	return ret;
> >  }
> > 
> >  static int find_crtc_index_in_state_by_stream(struct drm_atomic_state
> > *state, @@ -1253,9 +1279,9 @@ static bool
> > is_dsc_precompute_needed(struct drm_atomic_state *state)
> >  	return ret;
> >  }
> > 
> > -bool pre_validate_dsc(struct drm_atomic_state *state,
> > -		      struct dm_atomic_state **dm_state_ptr,
> > -		      struct dsc_mst_fairness_vars *vars)
> > +int pre_validate_dsc(struct drm_atomic_state *state,
> > +		     struct dm_atomic_state **dm_state_ptr,
> > +		     struct dsc_mst_fairness_vars *vars)
> >  {
> >  	int i;
> >  	struct dm_atomic_state *dm_state;
> > @@ -1264,11 +1290,12 @@ bool pre_validate_dsc(struct drm_atomic_state
> > *state,
> > 
> >  	if (!is_dsc_precompute_needed(state)) {
> >  		DRM_INFO_ONCE("DSC precompute is not needed.\n");
> > -		return true;
> > +		return 0;
> >  	}
> > -	if (dm_atomic_get_state(state, dm_state_ptr)) {
> > +	ret = dm_atomic_get_state(state, dm_state_ptr);
> > +	if (ret != 0) {
> >  		DRM_INFO_ONCE("dm_atomic_get_state() failed\n");
> > -		return false;
> > +		return ret;
> >  	}
> >  	dm_state = *dm_state_ptr;
> > 
> > @@ -1280,7 +1307,7 @@ bool pre_validate_dsc(struct drm_atomic_state
> > *state,
> > 
> >  	local_dc_state = kmemdup(dm_state->context, sizeof(struct
> > dc_state), GFP_KERNEL);
> >  	if (!local_dc_state)
> > -		return false;
> > +		return -ENOMEM;
> > 
> >  	for (i = 0; i < local_dc_state->stream_count; i++) {
> >  		struct dc_stream_state *stream = dm_state->context-
> > > streams[i]; @@ -1316,9 +1343,9 @@ bool pre_validate_dsc(struct
> > drm_atomic_state *state,
> >  	if (ret != 0)
> >  		goto clean_exit;
> > 
> > -	if (!pre_compute_mst_dsc_configs_for_state(state, local_dc_state,
> > vars)) {
> > +	ret = pre_compute_mst_dsc_configs_for_state(state, local_dc_state,
> > vars);
> > +	if (ret != 0) {
> > 
> > 	DRM_INFO_ONCE("pre_compute_mst_dsc_configs_for_state()
> > failed\n");
> > -		ret = -EINVAL;
> >  		goto clean_exit;
> >  	}
> > 
> > @@ -1349,7 +1376,7 @@ bool pre_validate_dsc(struct drm_atomic_state
> > *state,
> > 
> >  	kfree(local_dc_state);
> > 
> > -	return (ret == 0);
> > +	return ret;
> >  }
> > 
> >  static unsigned int kbps_from_pbn(unsigned int pbn) diff --git
> > a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> > index b92a7c5671aa2..97fd70df531bf 100644
> > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> > +++
> > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> > @@ -53,15 +53,15 @@ struct dsc_mst_fairness_vars {
> >  	struct amdgpu_dm_connector *aconnector;  };
> > 
> > -bool compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> > -				       struct dc_state *dc_state,
> > -				       struct dsc_mst_fairness_vars *vars);
> > +int compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> > +				      struct dc_state *dc_state,
> > +				      struct dsc_mst_fairness_vars *vars);
> > 
> >  bool needs_dsc_aux_workaround(struct dc_link *link);
> > 
> > -bool pre_validate_dsc(struct drm_atomic_state *state,
> > -		      struct dm_atomic_state **dm_state_ptr,
> > -		      struct dsc_mst_fairness_vars *vars);
> > +int pre_validate_dsc(struct drm_atomic_state *state,
> > +		     struct dm_atomic_state **dm_state_ptr,
> > +		     struct dsc_mst_fairness_vars *vars);
> > 
> >  enum dc_status dm_dp_mst_is_port_support_mode(
> >  	struct amdgpu_dm_connector *aconnector,
> > --
> > 2.37.3
>
  

JFYI, Coverity pointed out one more issue with this series so I'm going to
send out a respin real quick to fix it. It's just a missing variable
assignment (we leave ret unassigned by mistake in
pre_compute_mst_dsc_configs()) so I will carry over your r-b on it.

On Wed, 2022-11-16 at 04:39 +0000, Lin, Wayne wrote:
> [Public]
> 
> All the patch set looks good to me. Feel free to add:
> Reviewed-by: Wayne Lin <Wayne.Lin@amd.com>
> 
> Again, thank you Lyude for helping on this!!!
> 
> Regards,
> Wayne
> > -----Original Message-----
> > From: Lyude Paul <lyude@redhat.com>
> > Sent: Tuesday, November 15, 2022 6:18 AM
> > To: amd-gfx@lists.freedesktop.org
> > Cc: Wentland, Harry <Harry.Wentland@amd.com>; stable@vger.kernel.org;
> > Li, Sun peng (Leo) <Sunpeng.Li@amd.com>; Siqueira, Rodrigo
> > <Rodrigo.Siqueira@amd.com>; Deucher, Alexander
> > <Alexander.Deucher@amd.com>; Koenig, Christian
> > <Christian.Koenig@amd.com>; Pan, Xinhui <Xinhui.Pan@amd.com>; David
> > Airlie <airlied@gmail.com>; Daniel Vetter <daniel@ffwll.ch>; Kazlauskas,
> > Nicholas <Nicholas.Kazlauskas@amd.com>; Pillai, Aurabindo
> > <Aurabindo.Pillai@amd.com>; Li, Roman <Roman.Li@amd.com>; Zuo, Jerry
> > <Jerry.Zuo@amd.com>; Wu, Hersen <hersenxs.wu@amd.com>; Lin, Wayne
> > <Wayne.Lin@amd.com>; Thomas Zimmermann <tzimmermann@suse.de>;
> > Mahfooz, Hamza <Hamza.Mahfooz@amd.com>; Hung, Alex
> > <Alex.Hung@amd.com>; Mikita Lipski <mikita.lipski@amd.com>; Liu,
> > Wenjing <Wenjing.Liu@amd.com>; Francis, David
> > <David.Francis@amd.com>; open list:DRM DRIVERS <dri-
> > devel@lists.freedesktop.org>; open list <linux-kernel@vger.kernel.org>
> > Subject: [PATCH v2 1/4] drm/amdgpu/mst: Stop ignoring error codes and
> > deadlocking
> > 
> > It appears that amdgpu makes the mistake of completely ignoring the return
> > values from the DP MST helpers, and instead just returns a simple true/false.
> > In this case, it seems to have come back to bite us because as a result of
> > simply returning false from compute_mst_dsc_configs_for_state(), amdgpu
> > had no way of telling when a deadlock happened from these helpers. This
> > could definitely result in some kernel splats.
> > 
> > V2:
> > * Address Wayne's comments (fix another bunch of spots where we weren't
> >   passing down return codes)
> > 
> > Signed-off-by: Lyude Paul <lyude@redhat.com>
> > Fixes: 8c20a1ed9b4f ("drm/amd/display: MST DSC compute fair share")
> > Cc: Harry Wentland <harry.wentland@amd.com>
> > Cc: <stable@vger.kernel.org> # v5.6+
> > ---
> >  .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |  18 +-
> >  .../display/amdgpu_dm/amdgpu_dm_mst_types.c   | 235 ++++++++++------
> > --
> >  .../display/amdgpu_dm/amdgpu_dm_mst_types.h   |  12 +-
> >  3 files changed, 147 insertions(+), 118 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > index 0db2a88cd4d7b..852a2100c6b38 100644
> > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > @@ -6462,7 +6462,7 @@ static int
> > dm_update_mst_vcpi_slots_for_dsc(struct drm_atomic_state *state,
> >  	struct drm_connector_state *new_con_state;
> >  	struct amdgpu_dm_connector *aconnector;
> >  	struct dm_connector_state *dm_conn_state;
> > -	int i, j;
> > +	int i, j, ret;
> >  	int vcpi, pbn_div, pbn, slot_num = 0;
> > 
> >  	for_each_new_connector_in_state(state, connector,
> > new_con_state, i) { @@ -6509,8 +6509,11 @@ static int
> > dm_update_mst_vcpi_slots_for_dsc(struct drm_atomic_state *state,
> >  			dm_conn_state->pbn = pbn;
> >  			dm_conn_state->vcpi_slots = slot_num;
> > 
> > -			drm_dp_mst_atomic_enable_dsc(state, aconnector-
> > > port, dm_conn_state->pbn,
> > -						     false);
> > +			ret = drm_dp_mst_atomic_enable_dsc(state,
> > aconnector->port,
> > +							   dm_conn_state-
> > > pbn, false);
> > +			if (ret < 0)
> > +				return ret;
> > +
> >  			continue;
> >  		}
> > 
> > @@ -9523,10 +9526,9 @@ static int amdgpu_dm_atomic_check(struct
> > drm_device *dev,
> > 
> >  #if defined(CONFIG_DRM_AMD_DC_DCN)
> >  	if (dc_resource_is_dsc_encoding_supported(dc)) {
> > -		if (!pre_validate_dsc(state, &dm_state, vars)) {
> > -			ret = -EINVAL;
> > +		ret = pre_validate_dsc(state, &dm_state, vars);
> > +		if (ret != 0)
> >  			goto fail;
> > -		}
> >  	}
> >  #endif
> > 
> > @@ -9621,9 +9623,9 @@ static int amdgpu_dm_atomic_check(struct
> > drm_device *dev,
> >  		}
> > 
> >  #if defined(CONFIG_DRM_AMD_DC_DCN)
> > -		if (!compute_mst_dsc_configs_for_state(state, dm_state-
> > > context, vars)) {
> > +		ret = compute_mst_dsc_configs_for_state(state, dm_state-
> > > context, vars);
> > +		if (ret) {
> > 
> > 	DRM_DEBUG_DRIVER("compute_mst_dsc_configs_for_state()
> > failed\n");
> > -			ret = -EINVAL;
> >  			goto fail;
> >  		}
> > 
> > diff --git
> > a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > index 6ff96b4bdda5c..bba2e8aaa2c20 100644
> > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > +++
> > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > @@ -703,13 +703,13 @@ static int bpp_x16_from_pbn(struct
> > dsc_mst_fairness_params param, int pbn)
> >  	return dsc_config.bits_per_pixel;
> >  }
> > 
> > -static bool increase_dsc_bpp(struct drm_atomic_state *state,
> > -			     struct drm_dp_mst_topology_state *mst_state,
> > -			     struct dc_link *dc_link,
> > -			     struct dsc_mst_fairness_params *params,
> > -			     struct dsc_mst_fairness_vars *vars,
> > -			     int count,
> > -			     int k)
> > +static int increase_dsc_bpp(struct drm_atomic_state *state,
> > +			    struct drm_dp_mst_topology_state *mst_state,
> > +			    struct dc_link *dc_link,
> > +			    struct dsc_mst_fairness_params *params,
> > +			    struct dsc_mst_fairness_vars *vars,
> > +			    int count,
> > +			    int k)
> >  {
> >  	int i;
> >  	bool bpp_increased[MAX_PIPES];
> > @@ -719,6 +719,7 @@ static bool increase_dsc_bpp(struct
> > drm_atomic_state *state,
> >  	int remaining_to_increase = 0;
> >  	int link_timeslots_used;
> >  	int fair_pbn_alloc;
> > +	int ret = 0;
> > 
> >  	for (i = 0; i < count; i++) {
> >  		if (vars[i + k].dsc_enabled) {
> > @@ -757,52 +758,60 @@ static bool increase_dsc_bpp(struct
> > drm_atomic_state *state,
> > 
> >  		if (initial_slack[next_index] > fair_pbn_alloc) {
> >  			vars[next_index].pbn += fair_pbn_alloc;
> > -			if (drm_dp_atomic_find_time_slots(state,
> > -
> > params[next_index].port->mgr,
> > -
> > params[next_index].port,
> > -
> > vars[next_index].pbn) < 0)
> > -				return false;
> > -			if (!drm_dp_mst_atomic_check(state)) {
> > +			ret = drm_dp_atomic_find_time_slots(state,
> > +
> > params[next_index].port->mgr,
> > +
> > params[next_index].port,
> > +
> > vars[next_index].pbn);
> > +			if (ret < 0)
> > +				return ret;
> > +
> > +			ret = drm_dp_mst_atomic_check(state);
> > +			if (ret == 0) {
> >  				vars[next_index].bpp_x16 =
> > bpp_x16_from_pbn(params[next_index], vars[next_index].pbn);
> >  			} else {
> >  				vars[next_index].pbn -= fair_pbn_alloc;
> > -				if (drm_dp_atomic_find_time_slots(state,
> > -
> > params[next_index].port->mgr,
> > -
> > params[next_index].port,
> > -
> > vars[next_index].pbn) < 0)
> > -					return false;
> > +				ret = drm_dp_atomic_find_time_slots(state,
> > +
> > params[next_index].port->mgr,
> > +
> > params[next_index].port,
> > +
> > vars[next_index].pbn);
> > +				if (ret < 0)
> > +					return ret;
> >  			}
> >  		} else {
> >  			vars[next_index].pbn += initial_slack[next_index];
> > -			if (drm_dp_atomic_find_time_slots(state,
> > -
> > params[next_index].port->mgr,
> > -
> > params[next_index].port,
> > -
> > vars[next_index].pbn) < 0)
> > -				return false;
> > -			if (!drm_dp_mst_atomic_check(state)) {
> > +			ret = drm_dp_atomic_find_time_slots(state,
> > +
> > params[next_index].port->mgr,
> > +
> > params[next_index].port,
> > +
> > vars[next_index].pbn);
> > +			if (ret < 0)
> > +				return ret;
> > +
> > +			ret = drm_dp_mst_atomic_check(state);
> > +			if (ret == 0) {
> >  				vars[next_index].bpp_x16 =
> > params[next_index].bw_range.max_target_bpp_x16;
> >  			} else {
> >  				vars[next_index].pbn -=
> > initial_slack[next_index];
> > -				if (drm_dp_atomic_find_time_slots(state,
> > -
> > params[next_index].port->mgr,
> > -
> > params[next_index].port,
> > -
> > vars[next_index].pbn) < 0)
> > -					return false;
> > +				ret = drm_dp_atomic_find_time_slots(state,
> > +
> > params[next_index].port->mgr,
> > +
> > params[next_index].port,
> > +
> > vars[next_index].pbn);
> > +				if (ret < 0)
> > +					return ret;
> >  			}
> >  		}
> > 
> >  		bpp_increased[next_index] = true;
> >  		remaining_to_increase--;
> >  	}
> > -	return true;
> > +	return 0;
> >  }
> > 
> > -static bool try_disable_dsc(struct drm_atomic_state *state,
> > -			    struct dc_link *dc_link,
> > -			    struct dsc_mst_fairness_params *params,
> > -			    struct dsc_mst_fairness_vars *vars,
> > -			    int count,
> > -			    int k)
> > +static int try_disable_dsc(struct drm_atomic_state *state,
> > +			   struct dc_link *dc_link,
> > +			   struct dsc_mst_fairness_params *params,
> > +			   struct dsc_mst_fairness_vars *vars,
> > +			   int count,
> > +			   int k)
> >  {
> >  	int i;
> >  	bool tried[MAX_PIPES];
> > @@ -810,6 +819,7 @@ static bool try_disable_dsc(struct drm_atomic_state
> > *state,
> >  	int max_kbps_increase;
> >  	int next_index;
> >  	int remaining_to_try = 0;
> > +	int ret;
> > 
> >  	for (i = 0; i < count; i++) {
> >  		if (vars[i + k].dsc_enabled
> > @@ -840,49 +850,52 @@ static bool try_disable_dsc(struct
> > drm_atomic_state *state,
> >  			break;
> > 
> >  		vars[next_index].pbn =
> > kbps_to_peak_pbn(params[next_index].bw_range.stream_kbps);
> > -		if (drm_dp_atomic_find_time_slots(state,
> > -						  params[next_index].port-
> > > mgr,
> > -						  params[next_index].port,
> > -						  vars[next_index].pbn) < 0)
> > -			return false;
> > +		ret = drm_dp_atomic_find_time_slots(state,
> > +						    params[next_index].port-
> > > mgr,
> > +						    params[next_index].port,
> > +						    vars[next_index].pbn);
> > +		if (ret < 0)
> > +			return ret;
> > 
> > -		if (!drm_dp_mst_atomic_check(state)) {
> > +		ret = drm_dp_mst_atomic_check(state);
> > +		if (ret == 0) {
> >  			vars[next_index].dsc_enabled = false;
> >  			vars[next_index].bpp_x16 = 0;
> >  		} else {
> >  			vars[next_index].pbn =
> > kbps_to_peak_pbn(params[next_index].bw_range.max_kbps);
> > -			if (drm_dp_atomic_find_time_slots(state,
> > -
> > params[next_index].port->mgr,
> > -
> > params[next_index].port,
> > -
> > vars[next_index].pbn) < 0)
> > -				return false;
> > +			ret = drm_dp_atomic_find_time_slots(state,
> > +
> > params[next_index].port->mgr,
> > +
> > params[next_index].port,
> > +
> > vars[next_index].pbn);
> > +			if (ret < 0)
> > +				return ret;
> >  		}
> > 
> >  		tried[next_index] = true;
> >  		remaining_to_try--;
> >  	}
> > -	return true;
> > +	return 0;
> >  }
> > 
> > -static bool compute_mst_dsc_configs_for_link(struct drm_atomic_state
> > *state,
> > -					     struct dc_state *dc_state,
> > -					     struct dc_link *dc_link,
> > -					     struct dsc_mst_fairness_vars *vars,
> > -					     struct drm_dp_mst_topology_mgr
> > *mgr,
> > -					     int *link_vars_start_index)
> > +static int compute_mst_dsc_configs_for_link(struct drm_atomic_state
> > *state,
> > +					    struct dc_state *dc_state,
> > +					    struct dc_link *dc_link,
> > +					    struct dsc_mst_fairness_vars *vars,
> > +					    struct drm_dp_mst_topology_mgr
> > *mgr,
> > +					    int *link_vars_start_index)
> >  {
> >  	struct dc_stream_state *stream;
> >  	struct dsc_mst_fairness_params params[MAX_PIPES];
> >  	struct amdgpu_dm_connector *aconnector;
> >  	struct drm_dp_mst_topology_state *mst_state =
> > drm_atomic_get_mst_topology_state(state, mgr);
> >  	int count = 0;
> > -	int i, k;
> > +	int i, k, ret;
> >  	bool debugfs_overwrite = false;
> > 
> >  	memset(params, 0, sizeof(params));
> > 
> >  	if (IS_ERR(mst_state))
> > -		return false;
> > +		return PTR_ERR(mst_state);
> > 
> >  	mst_state->pbn_div = dm_mst_get_pbn_divider(dc_link);  #if
> > defined(CONFIG_DRM_AMD_DC_DCN) @@ -933,7 +946,7 @@ static bool
> > compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,
> > 
> >  	if (count == 0) {
> >  		ASSERT(0);
> > -		return true;
> > +		return 0;
> >  	}
> > 
> >  	/* k is start index of vars for current phy link used by mst hub */ @@
> > -947,13 +960,17 @@ static bool compute_mst_dsc_configs_for_link(struct
> > drm_atomic_state *state,
> >  		vars[i + k].pbn =
> > kbps_to_peak_pbn(params[i].bw_range.stream_kbps);
> >  		vars[i + k].dsc_enabled = false;
> >  		vars[i + k].bpp_x16 = 0;
> > -		if (drm_dp_atomic_find_time_slots(state, params[i].port-
> > > mgr, params[i].port,
> > -						  vars[i + k].pbn) < 0)
> > -			return false;
> > +		ret = drm_dp_atomic_find_time_slots(state, params[i].port-
> > > mgr, params[i].port,
> > +						    vars[i + k].pbn);
> > +		if (ret < 0)
> > +			return ret;
> >  	}
> > -	if (!drm_dp_mst_atomic_check(state) && !debugfs_overwrite) {
> > +	ret = drm_dp_mst_atomic_check(state);
> > +	if (ret == 0 && !debugfs_overwrite) {
> >  		set_dsc_configs_from_fairness_vars(params, vars, count, k);
> > -		return true;
> > +		return 0;
> > +	} else if (ret != -ENOSPC) {
> > +		return ret;
> >  	}
> > 
> >  	/* Try max compression */
> > @@ -962,31 +979,36 @@ static bool
> > compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,
> >  			vars[i + k].pbn =
> > kbps_to_peak_pbn(params[i].bw_range.min_kbps);
> >  			vars[i + k].dsc_enabled = true;
> >  			vars[i + k].bpp_x16 =
> > params[i].bw_range.min_target_bpp_x16;
> > -			if (drm_dp_atomic_find_time_slots(state,
> > params[i].port->mgr,
> > -							  params[i].port, vars[i
> > + k].pbn) < 0)
> > -				return false;
> > +			ret = drm_dp_atomic_find_time_slots(state,
> > params[i].port->mgr,
> > +							    params[i].port,
> > vars[i + k].pbn);
> > +			if (ret < 0)
> > +				return ret;
> >  		} else {
> >  			vars[i + k].pbn =
> > kbps_to_peak_pbn(params[i].bw_range.stream_kbps);
> >  			vars[i + k].dsc_enabled = false;
> >  			vars[i + k].bpp_x16 = 0;
> > -			if (drm_dp_atomic_find_time_slots(state,
> > params[i].port->mgr,
> > -							  params[i].port, vars[i
> > + k].pbn) < 0)
> > -				return false;
> > +			ret = drm_dp_atomic_find_time_slots(state,
> > params[i].port->mgr,
> > +							    params[i].port,
> > vars[i + k].pbn);
> > +			if (ret < 0)
> > +				return ret;
> >  		}
> >  	}
> > -	if (drm_dp_mst_atomic_check(state))
> > -		return false;
> > +	ret = drm_dp_mst_atomic_check(state);
> > +	if (ret != 0)
> > +		return ret;
> > 
> >  	/* Optimize degree of compression */
> > -	if (!increase_dsc_bpp(state, mst_state, dc_link, params, vars, count,
> > k))
> > -		return false;
> > +	ret = increase_dsc_bpp(state, mst_state, dc_link, params, vars,
> > count, k);
> > +	if (ret < 0)
> > +		return ret;
> > 
> > -	if (!try_disable_dsc(state, dc_link, params, vars, count, k))
> > -		return false;
> > +	ret = try_disable_dsc(state, dc_link, params, vars, count, k);
> > +	if (ret < 0)
> > +		return ret;
> > 
> >  	set_dsc_configs_from_fairness_vars(params, vars, count, k);
> > 
> > -	return true;
> > +	return 0;
> >  }
> > 
> >  static bool is_dsc_need_re_compute(
> > @@ -1087,15 +1109,16 @@ static bool is_dsc_need_re_compute(
> >  	return is_dsc_need_re_compute;
> >  }
> > 
> > -bool compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> > -				       struct dc_state *dc_state,
> > -				       struct dsc_mst_fairness_vars *vars)
> > +int compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> > +				      struct dc_state *dc_state,
> > +				      struct dsc_mst_fairness_vars *vars)
> >  {
> >  	int i, j;
> >  	struct dc_stream_state *stream;
> >  	bool computed_streams[MAX_PIPES];
> >  	struct amdgpu_dm_connector *aconnector;
> >  	int link_vars_start_index = 0;
> > +	int ret = 0;
> > 
> >  	for (i = 0; i < dc_state->stream_count; i++)
> >  		computed_streams[i] = false;
> > @@ -1118,17 +1141,19 @@ bool compute_mst_dsc_configs_for_state(struct
> > drm_atomic_state *state,
> >  			continue;
> > 
> >  		if (dcn20_remove_stream_from_ctx(stream->ctx->dc,
> > dc_state, stream) != DC_OK)
> > -			return false;
> > +			return -EINVAL;
> > 
> >  		if (!is_dsc_need_re_compute(state, dc_state, stream->link))
> >  			continue;
> > 
> >  		mutex_lock(&aconnector->mst_mgr.lock);
> > -		if (!compute_mst_dsc_configs_for_link(state, dc_state,
> > stream->link, vars,
> > -						      &aconnector->mst_mgr,
> > -						      &link_vars_start_index)) {
> > +
> > +		ret = compute_mst_dsc_configs_for_link(state, dc_state,
> > stream->link, vars,
> > +						       &aconnector->mst_mgr,
> > +						       &link_vars_start_index);
> > +		if (ret != 0) {
> >  			mutex_unlock(&aconnector->mst_mgr.lock);
> > -			return false;
> > +			return ret;
> >  		}
> >  		mutex_unlock(&aconnector->mst_mgr.lock);
> > 
> > @@ -1143,22 +1168,22 @@ bool compute_mst_dsc_configs_for_state(struct
> > drm_atomic_state *state,
> > 
> >  		if (stream->timing.flags.DSC == 1)
> >  			if (dc_stream_add_dsc_to_resource(stream->ctx-
> > > dc, dc_state, stream) != DC_OK)
> > -				return false;
> > +				return -EINVAL;
> >  	}
> > 
> > -	return true;
> > +	return ret;
> >  }
> > 
> > -static bool
> > -	pre_compute_mst_dsc_configs_for_state(struct drm_atomic_state
> > *state,
> > -					      struct dc_state *dc_state,
> > -					      struct dsc_mst_fairness_vars
> > *vars)
> > +static int pre_compute_mst_dsc_configs_for_state(struct
> > drm_atomic_state *state,
> > +						 struct dc_state *dc_state,
> > +						 struct dsc_mst_fairness_vars
> > *vars)
> >  {
> >  	int i, j;
> >  	struct dc_stream_state *stream;
> >  	bool computed_streams[MAX_PIPES];
> >  	struct amdgpu_dm_connector *aconnector;
> >  	int link_vars_start_index = 0;
> > +	int ret;
> > 
> >  	for (i = 0; i < dc_state->stream_count; i++)
> >  		computed_streams[i] = false;
> > @@ -1184,11 +1209,12 @@ static bool
> >  			continue;
> > 
> >  		mutex_lock(&aconnector->mst_mgr.lock);
> > -		if (!compute_mst_dsc_configs_for_link(state, dc_state,
> > stream->link, vars,
> > -						      &aconnector->mst_mgr,
> > -						      &link_vars_start_index)) {
> > +		ret = compute_mst_dsc_configs_for_link(state, dc_state,
> > stream->link, vars,
> > +						       &aconnector->mst_mgr,
> > +						       &link_vars_start_index);
> > +		if (ret != 0) {
> >  			mutex_unlock(&aconnector->mst_mgr.lock);
> > -			return false;
> > +			return ret;
> >  		}
> >  		mutex_unlock(&aconnector->mst_mgr.lock);
> > 
> > @@ -1198,7 +1224,7 @@ static bool
> >  		}
> >  	}
> > 
> > -	return true;
> > +	return ret;
> >  }
> > 
> >  static int find_crtc_index_in_state_by_stream(struct drm_atomic_state
> > *state, @@ -1253,9 +1279,9 @@ static bool
> > is_dsc_precompute_needed(struct drm_atomic_state *state)
> >  	return ret;
> >  }
> > 
> > -bool pre_validate_dsc(struct drm_atomic_state *state,
> > -		      struct dm_atomic_state **dm_state_ptr,
> > -		      struct dsc_mst_fairness_vars *vars)
> > +int pre_validate_dsc(struct drm_atomic_state *state,
> > +		     struct dm_atomic_state **dm_state_ptr,
> > +		     struct dsc_mst_fairness_vars *vars)
> >  {
> >  	int i;
> >  	struct dm_atomic_state *dm_state;
> > @@ -1264,11 +1290,12 @@ bool pre_validate_dsc(struct drm_atomic_state
> > *state,
> > 
> >  	if (!is_dsc_precompute_needed(state)) {
> >  		DRM_INFO_ONCE("DSC precompute is not needed.\n");
> > -		return true;
> > +		return 0;
> >  	}
> > -	if (dm_atomic_get_state(state, dm_state_ptr)) {
> > +	ret = dm_atomic_get_state(state, dm_state_ptr);
> > +	if (ret != 0) {
> >  		DRM_INFO_ONCE("dm_atomic_get_state() failed\n");
> > -		return false;
> > +		return ret;
> >  	}
> >  	dm_state = *dm_state_ptr;
> > 
> > @@ -1280,7 +1307,7 @@ bool pre_validate_dsc(struct drm_atomic_state
> > *state,
> > 
> >  	local_dc_state = kmemdup(dm_state->context, sizeof(struct
> > dc_state), GFP_KERNEL);
> >  	if (!local_dc_state)
> > -		return false;
> > +		return -ENOMEM;
> > 
> >  	for (i = 0; i < local_dc_state->stream_count; i++) {
> >  		struct dc_stream_state *stream = dm_state->context-
> > > streams[i]; @@ -1316,9 +1343,9 @@ bool pre_validate_dsc(struct
> > drm_atomic_state *state,
> >  	if (ret != 0)
> >  		goto clean_exit;
> > 
> > -	if (!pre_compute_mst_dsc_configs_for_state(state, local_dc_state,
> > vars)) {
> > +	ret = pre_compute_mst_dsc_configs_for_state(state, local_dc_state,
> > vars);
> > +	if (ret != 0) {
> > 
> > 	DRM_INFO_ONCE("pre_compute_mst_dsc_configs_for_state()
> > failed\n");
> > -		ret = -EINVAL;
> >  		goto clean_exit;
> >  	}
> > 
> > @@ -1349,7 +1376,7 @@ bool pre_validate_dsc(struct drm_atomic_state
> > *state,
> > 
> >  	kfree(local_dc_state);
> > 
> > -	return (ret == 0);
> > +	return ret;
> >  }
> > 
> >  static unsigned int kbps_from_pbn(unsigned int pbn) diff --git
> > a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> > index b92a7c5671aa2..97fd70df531bf 100644
> > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> > +++
> > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> > @@ -53,15 +53,15 @@ struct dsc_mst_fairness_vars {
> >  	struct amdgpu_dm_connector *aconnector;  };
> > 
> > -bool compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> > -				       struct dc_state *dc_state,
> > -				       struct dsc_mst_fairness_vars *vars);
> > +int compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> > +				      struct dc_state *dc_state,
> > +				      struct dsc_mst_fairness_vars *vars);
> > 
> >  bool needs_dsc_aux_workaround(struct dc_link *link);
> > 
> > -bool pre_validate_dsc(struct drm_atomic_state *state,
> > -		      struct dm_atomic_state **dm_state_ptr,
> > -		      struct dsc_mst_fairness_vars *vars);
> > +int pre_validate_dsc(struct drm_atomic_state *state,
> > +		     struct dm_atomic_state **dm_state_ptr,
> > +		     struct dsc_mst_fairness_vars *vars);
> > 
> >  enum dc_status dm_dp_mst_is_port_support_mode(
> >  	struct amdgpu_dm_connector *aconnector,
> > --
> > 2.37.3
>
  

I've already picked this up.  Can you send a follow up patch with just
the coverity fix?

Alex

On Fri, Nov 18, 2022 at 2:17 PM Lyude Paul <lyude@redhat.com> wrote:
>
> JFYI, Coverity pointed out one more issue with this series so I'm going to
> send out a respin real quick to fix it. It's just a missing variable
> assignment (we leave ret unassigned by mistake in
> pre_compute_mst_dsc_configs()) so I will carry over your r-b on it.
>
> On Wed, 2022-11-16 at 04:39 +0000, Lin, Wayne wrote:
> > [Public]
> >
> > All the patch set looks good to me. Feel free to add:
> > Reviewed-by: Wayne Lin <Wayne.Lin@amd.com>
> >
> > Again, thank you Lyude for helping on this!!!
> >
> > Regards,
> > Wayne
> > > -----Original Message-----
> > > From: Lyude Paul <lyude@redhat.com>
> > > Sent: Tuesday, November 15, 2022 6:18 AM
> > > To: amd-gfx@lists.freedesktop.org
> > > Cc: Wentland, Harry <Harry.Wentland@amd.com>; stable@vger.kernel.org;
> > > Li, Sun peng (Leo) <Sunpeng.Li@amd.com>; Siqueira, Rodrigo
> > > <Rodrigo.Siqueira@amd.com>; Deucher, Alexander
> > > <Alexander.Deucher@amd.com>; Koenig, Christian
> > > <Christian.Koenig@amd.com>; Pan, Xinhui <Xinhui.Pan@amd.com>; David
> > > Airlie <airlied@gmail.com>; Daniel Vetter <daniel@ffwll.ch>; Kazlauskas,
> > > Nicholas <Nicholas.Kazlauskas@amd.com>; Pillai, Aurabindo
> > > <Aurabindo.Pillai@amd.com>; Li, Roman <Roman.Li@amd.com>; Zuo, Jerry
> > > <Jerry.Zuo@amd.com>; Wu, Hersen <hersenxs.wu@amd.com>; Lin, Wayne
> > > <Wayne.Lin@amd.com>; Thomas Zimmermann <tzimmermann@suse.de>;
> > > Mahfooz, Hamza <Hamza.Mahfooz@amd.com>; Hung, Alex
> > > <Alex.Hung@amd.com>; Mikita Lipski <mikita.lipski@amd.com>; Liu,
> > > Wenjing <Wenjing.Liu@amd.com>; Francis, David
> > > <David.Francis@amd.com>; open list:DRM DRIVERS <dri-
> > > devel@lists.freedesktop.org>; open list <linux-kernel@vger.kernel.org>
> > > Subject: [PATCH v2 1/4] drm/amdgpu/mst: Stop ignoring error codes and
> > > deadlocking
> > >
> > > It appears that amdgpu makes the mistake of completely ignoring the return
> > > values from the DP MST helpers, and instead just returns a simple true/false.
> > > In this case, it seems to have come back to bite us because as a result of
> > > simply returning false from compute_mst_dsc_configs_for_state(), amdgpu
> > > had no way of telling when a deadlock happened from these helpers. This
> > > could definitely result in some kernel splats.
> > >
> > > V2:
> > > * Address Wayne's comments (fix another bunch of spots where we weren't
> > >   passing down return codes)
> > >
> > > Signed-off-by: Lyude Paul <lyude@redhat.com>
> > > Fixes: 8c20a1ed9b4f ("drm/amd/display: MST DSC compute fair share")
> > > Cc: Harry Wentland <harry.wentland@amd.com>
> > > Cc: <stable@vger.kernel.org> # v5.6+
> > > ---
> > >  .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |  18 +-
> > >  .../display/amdgpu_dm/amdgpu_dm_mst_types.c   | 235 ++++++++++------
> > > --
> > >  .../display/amdgpu_dm/amdgpu_dm_mst_types.h   |  12 +-
> > >  3 files changed, 147 insertions(+), 118 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > > index 0db2a88cd4d7b..852a2100c6b38 100644
> > > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > > +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > > @@ -6462,7 +6462,7 @@ static int
> > > dm_update_mst_vcpi_slots_for_dsc(struct drm_atomic_state *state,
> > >     struct drm_connector_state *new_con_state;
> > >     struct amdgpu_dm_connector *aconnector;
> > >     struct dm_connector_state *dm_conn_state;
> > > -   int i, j;
> > > +   int i, j, ret;
> > >     int vcpi, pbn_div, pbn, slot_num = 0;
> > >
> > >     for_each_new_connector_in_state(state, connector,
> > > new_con_state, i) { @@ -6509,8 +6509,11 @@ static int
> > > dm_update_mst_vcpi_slots_for_dsc(struct drm_atomic_state *state,
> > >                     dm_conn_state->pbn = pbn;
> > >                     dm_conn_state->vcpi_slots = slot_num;
> > >
> > > -                   drm_dp_mst_atomic_enable_dsc(state, aconnector-
> > > > port, dm_conn_state->pbn,
> > > -                                                false);
> > > +                   ret = drm_dp_mst_atomic_enable_dsc(state,
> > > aconnector->port,
> > > +                                                      dm_conn_state-
> > > > pbn, false);
> > > +                   if (ret < 0)
> > > +                           return ret;
> > > +
> > >                     continue;
> > >             }
> > >
> > > @@ -9523,10 +9526,9 @@ static int amdgpu_dm_atomic_check(struct
> > > drm_device *dev,
> > >
> > >  #if defined(CONFIG_DRM_AMD_DC_DCN)
> > >     if (dc_resource_is_dsc_encoding_supported(dc)) {
> > > -           if (!pre_validate_dsc(state, &dm_state, vars)) {
> > > -                   ret = -EINVAL;
> > > +           ret = pre_validate_dsc(state, &dm_state, vars);
> > > +           if (ret != 0)
> > >                     goto fail;
> > > -           }
> > >     }
> > >  #endif
> > >
> > > @@ -9621,9 +9623,9 @@ static int amdgpu_dm_atomic_check(struct
> > > drm_device *dev,
> > >             }
> > >
> > >  #if defined(CONFIG_DRM_AMD_DC_DCN)
> > > -           if (!compute_mst_dsc_configs_for_state(state, dm_state-
> > > > context, vars)) {
> > > +           ret = compute_mst_dsc_configs_for_state(state, dm_state-
> > > > context, vars);
> > > +           if (ret) {
> > >
> > >     DRM_DEBUG_DRIVER("compute_mst_dsc_configs_for_state()
> > > failed\n");
> > > -                   ret = -EINVAL;
> > >                     goto fail;
> > >             }
> > >
> > > diff --git
> > > a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > > index 6ff96b4bdda5c..bba2e8aaa2c20 100644
> > > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > > +++
> > > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > > @@ -703,13 +703,13 @@ static int bpp_x16_from_pbn(struct
> > > dsc_mst_fairness_params param, int pbn)
> > >     return dsc_config.bits_per_pixel;
> > >  }
> > >
> > > -static bool increase_dsc_bpp(struct drm_atomic_state *state,
> > > -                        struct drm_dp_mst_topology_state *mst_state,
> > > -                        struct dc_link *dc_link,
> > > -                        struct dsc_mst_fairness_params *params,
> > > -                        struct dsc_mst_fairness_vars *vars,
> > > -                        int count,
> > > -                        int k)
> > > +static int increase_dsc_bpp(struct drm_atomic_state *state,
> > > +                       struct drm_dp_mst_topology_state *mst_state,
> > > +                       struct dc_link *dc_link,
> > > +                       struct dsc_mst_fairness_params *params,
> > > +                       struct dsc_mst_fairness_vars *vars,
> > > +                       int count,
> > > +                       int k)
> > >  {
> > >     int i;
> > >     bool bpp_increased[MAX_PIPES];
> > > @@ -719,6 +719,7 @@ static bool increase_dsc_bpp(struct
> > > drm_atomic_state *state,
> > >     int remaining_to_increase = 0;
> > >     int link_timeslots_used;
> > >     int fair_pbn_alloc;
> > > +   int ret = 0;
> > >
> > >     for (i = 0; i < count; i++) {
> > >             if (vars[i + k].dsc_enabled) {
> > > @@ -757,52 +758,60 @@ static bool increase_dsc_bpp(struct
> > > drm_atomic_state *state,
> > >
> > >             if (initial_slack[next_index] > fair_pbn_alloc) {
> > >                     vars[next_index].pbn += fair_pbn_alloc;
> > > -                   if (drm_dp_atomic_find_time_slots(state,
> > > -
> > > params[next_index].port->mgr,
> > > -
> > > params[next_index].port,
> > > -
> > > vars[next_index].pbn) < 0)
> > > -                           return false;
> > > -                   if (!drm_dp_mst_atomic_check(state)) {
> > > +                   ret = drm_dp_atomic_find_time_slots(state,
> > > +
> > > params[next_index].port->mgr,
> > > +
> > > params[next_index].port,
> > > +
> > > vars[next_index].pbn);
> > > +                   if (ret < 0)
> > > +                           return ret;
> > > +
> > > +                   ret = drm_dp_mst_atomic_check(state);
> > > +                   if (ret == 0) {
> > >                             vars[next_index].bpp_x16 =
> > > bpp_x16_from_pbn(params[next_index], vars[next_index].pbn);
> > >                     } else {
> > >                             vars[next_index].pbn -= fair_pbn_alloc;
> > > -                           if (drm_dp_atomic_find_time_slots(state,
> > > -
> > > params[next_index].port->mgr,
> > > -
> > > params[next_index].port,
> > > -
> > > vars[next_index].pbn) < 0)
> > > -                                   return false;
> > > +                           ret = drm_dp_atomic_find_time_slots(state,
> > > +
> > > params[next_index].port->mgr,
> > > +
> > > params[next_index].port,
> > > +
> > > vars[next_index].pbn);
> > > +                           if (ret < 0)
> > > +                                   return ret;
> > >                     }
> > >             } else {
> > >                     vars[next_index].pbn += initial_slack[next_index];
> > > -                   if (drm_dp_atomic_find_time_slots(state,
> > > -
> > > params[next_index].port->mgr,
> > > -
> > > params[next_index].port,
> > > -
> > > vars[next_index].pbn) < 0)
> > > -                           return false;
> > > -                   if (!drm_dp_mst_atomic_check(state)) {
> > > +                   ret = drm_dp_atomic_find_time_slots(state,
> > > +
> > > params[next_index].port->mgr,
> > > +
> > > params[next_index].port,
> > > +
> > > vars[next_index].pbn);
> > > +                   if (ret < 0)
> > > +                           return ret;
> > > +
> > > +                   ret = drm_dp_mst_atomic_check(state);
> > > +                   if (ret == 0) {
> > >                             vars[next_index].bpp_x16 =
> > > params[next_index].bw_range.max_target_bpp_x16;
> > >                     } else {
> > >                             vars[next_index].pbn -=
> > > initial_slack[next_index];
> > > -                           if (drm_dp_atomic_find_time_slots(state,
> > > -
> > > params[next_index].port->mgr,
> > > -
> > > params[next_index].port,
> > > -
> > > vars[next_index].pbn) < 0)
> > > -                                   return false;
> > > +                           ret = drm_dp_atomic_find_time_slots(state,
> > > +
> > > params[next_index].port->mgr,
> > > +
> > > params[next_index].port,
> > > +
> > > vars[next_index].pbn);
> > > +                           if (ret < 0)
> > > +                                   return ret;
> > >                     }
> > >             }
> > >
> > >             bpp_increased[next_index] = true;
> > >             remaining_to_increase--;
> > >     }
> > > -   return true;
> > > +   return 0;
> > >  }
> > >
> > > -static bool try_disable_dsc(struct drm_atomic_state *state,
> > > -                       struct dc_link *dc_link,
> > > -                       struct dsc_mst_fairness_params *params,
> > > -                       struct dsc_mst_fairness_vars *vars,
> > > -                       int count,
> > > -                       int k)
> > > +static int try_disable_dsc(struct drm_atomic_state *state,
> > > +                      struct dc_link *dc_link,
> > > +                      struct dsc_mst_fairness_params *params,
> > > +                      struct dsc_mst_fairness_vars *vars,
> > > +                      int count,
> > > +                      int k)
> > >  {
> > >     int i;
> > >     bool tried[MAX_PIPES];
> > > @@ -810,6 +819,7 @@ static bool try_disable_dsc(struct drm_atomic_state
> > > *state,
> > >     int max_kbps_increase;
> > >     int next_index;
> > >     int remaining_to_try = 0;
> > > +   int ret;
> > >
> > >     for (i = 0; i < count; i++) {
> > >             if (vars[i + k].dsc_enabled
> > > @@ -840,49 +850,52 @@ static bool try_disable_dsc(struct
> > > drm_atomic_state *state,
> > >                     break;
> > >
> > >             vars[next_index].pbn =
> > > kbps_to_peak_pbn(params[next_index].bw_range.stream_kbps);
> > > -           if (drm_dp_atomic_find_time_slots(state,
> > > -                                             params[next_index].port-
> > > > mgr,
> > > -                                             params[next_index].port,
> > > -                                             vars[next_index].pbn) < 0)
> > > -                   return false;
> > > +           ret = drm_dp_atomic_find_time_slots(state,
> > > +                                               params[next_index].port-
> > > > mgr,
> > > +                                               params[next_index].port,
> > > +                                               vars[next_index].pbn);
> > > +           if (ret < 0)
> > > +                   return ret;
> > >
> > > -           if (!drm_dp_mst_atomic_check(state)) {
> > > +           ret = drm_dp_mst_atomic_check(state);
> > > +           if (ret == 0) {
> > >                     vars[next_index].dsc_enabled = false;
> > >                     vars[next_index].bpp_x16 = 0;
> > >             } else {
> > >                     vars[next_index].pbn =
> > > kbps_to_peak_pbn(params[next_index].bw_range.max_kbps);
> > > -                   if (drm_dp_atomic_find_time_slots(state,
> > > -
> > > params[next_index].port->mgr,
> > > -
> > > params[next_index].port,
> > > -
> > > vars[next_index].pbn) < 0)
> > > -                           return false;
> > > +                   ret = drm_dp_atomic_find_time_slots(state,
> > > +
> > > params[next_index].port->mgr,
> > > +
> > > params[next_index].port,
> > > +
> > > vars[next_index].pbn);
> > > +                   if (ret < 0)
> > > +                           return ret;
> > >             }
> > >
> > >             tried[next_index] = true;
> > >             remaining_to_try--;
> > >     }
> > > -   return true;
> > > +   return 0;
> > >  }
> > >
> > > -static bool compute_mst_dsc_configs_for_link(struct drm_atomic_state
> > > *state,
> > > -                                        struct dc_state *dc_state,
> > > -                                        struct dc_link *dc_link,
> > > -                                        struct dsc_mst_fairness_vars *vars,
> > > -                                        struct drm_dp_mst_topology_mgr
> > > *mgr,
> > > -                                        int *link_vars_start_index)
> > > +static int compute_mst_dsc_configs_for_link(struct drm_atomic_state
> > > *state,
> > > +                                       struct dc_state *dc_state,
> > > +                                       struct dc_link *dc_link,
> > > +                                       struct dsc_mst_fairness_vars *vars,
> > > +                                       struct drm_dp_mst_topology_mgr
> > > *mgr,
> > > +                                       int *link_vars_start_index)
> > >  {
> > >     struct dc_stream_state *stream;
> > >     struct dsc_mst_fairness_params params[MAX_PIPES];
> > >     struct amdgpu_dm_connector *aconnector;
> > >     struct drm_dp_mst_topology_state *mst_state =
> > > drm_atomic_get_mst_topology_state(state, mgr);
> > >     int count = 0;
> > > -   int i, k;
> > > +   int i, k, ret;
> > >     bool debugfs_overwrite = false;
> > >
> > >     memset(params, 0, sizeof(params));
> > >
> > >     if (IS_ERR(mst_state))
> > > -           return false;
> > > +           return PTR_ERR(mst_state);
> > >
> > >     mst_state->pbn_div = dm_mst_get_pbn_divider(dc_link);  #if
> > > defined(CONFIG_DRM_AMD_DC_DCN) @@ -933,7 +946,7 @@ static bool
> > > compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,
> > >
> > >     if (count == 0) {
> > >             ASSERT(0);
> > > -           return true;
> > > +           return 0;
> > >     }
> > >
> > >     /* k is start index of vars for current phy link used by mst hub */ @@
> > > -947,13 +960,17 @@ static bool compute_mst_dsc_configs_for_link(struct
> > > drm_atomic_state *state,
> > >             vars[i + k].pbn =
> > > kbps_to_peak_pbn(params[i].bw_range.stream_kbps);
> > >             vars[i + k].dsc_enabled = false;
> > >             vars[i + k].bpp_x16 = 0;
> > > -           if (drm_dp_atomic_find_time_slots(state, params[i].port-
> > > > mgr, params[i].port,
> > > -                                             vars[i + k].pbn) < 0)
> > > -                   return false;
> > > +           ret = drm_dp_atomic_find_time_slots(state, params[i].port-
> > > > mgr, params[i].port,
> > > +                                               vars[i + k].pbn);
> > > +           if (ret < 0)
> > > +                   return ret;
> > >     }
> > > -   if (!drm_dp_mst_atomic_check(state) && !debugfs_overwrite) {
> > > +   ret = drm_dp_mst_atomic_check(state);
> > > +   if (ret == 0 && !debugfs_overwrite) {
> > >             set_dsc_configs_from_fairness_vars(params, vars, count, k);
> > > -           return true;
> > > +           return 0;
> > > +   } else if (ret != -ENOSPC) {
> > > +           return ret;
> > >     }
> > >
> > >     /* Try max compression */
> > > @@ -962,31 +979,36 @@ static bool
> > > compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,
> > >                     vars[i + k].pbn =
> > > kbps_to_peak_pbn(params[i].bw_range.min_kbps);
> > >                     vars[i + k].dsc_enabled = true;
> > >                     vars[i + k].bpp_x16 =
> > > params[i].bw_range.min_target_bpp_x16;
> > > -                   if (drm_dp_atomic_find_time_slots(state,
> > > params[i].port->mgr,
> > > -                                                     params[i].port, vars[i
> > > + k].pbn) < 0)
> > > -                           return false;
> > > +                   ret = drm_dp_atomic_find_time_slots(state,
> > > params[i].port->mgr,
> > > +                                                       params[i].port,
> > > vars[i + k].pbn);
> > > +                   if (ret < 0)
> > > +                           return ret;
> > >             } else {
> > >                     vars[i + k].pbn =
> > > kbps_to_peak_pbn(params[i].bw_range.stream_kbps);
> > >                     vars[i + k].dsc_enabled = false;
> > >                     vars[i + k].bpp_x16 = 0;
> > > -                   if (drm_dp_atomic_find_time_slots(state,
> > > params[i].port->mgr,
> > > -                                                     params[i].port, vars[i
> > > + k].pbn) < 0)
> > > -                           return false;
> > > +                   ret = drm_dp_atomic_find_time_slots(state,
> > > params[i].port->mgr,
> > > +                                                       params[i].port,
> > > vars[i + k].pbn);
> > > +                   if (ret < 0)
> > > +                           return ret;
> > >             }
> > >     }
> > > -   if (drm_dp_mst_atomic_check(state))
> > > -           return false;
> > > +   ret = drm_dp_mst_atomic_check(state);
> > > +   if (ret != 0)
> > > +           return ret;
> > >
> > >     /* Optimize degree of compression */
> > > -   if (!increase_dsc_bpp(state, mst_state, dc_link, params, vars, count,
> > > k))
> > > -           return false;
> > > +   ret = increase_dsc_bpp(state, mst_state, dc_link, params, vars,
> > > count, k);
> > > +   if (ret < 0)
> > > +           return ret;
> > >
> > > -   if (!try_disable_dsc(state, dc_link, params, vars, count, k))
> > > -           return false;
> > > +   ret = try_disable_dsc(state, dc_link, params, vars, count, k);
> > > +   if (ret < 0)
> > > +           return ret;
> > >
> > >     set_dsc_configs_from_fairness_vars(params, vars, count, k);
> > >
> > > -   return true;
> > > +   return 0;
> > >  }
> > >
> > >  static bool is_dsc_need_re_compute(
> > > @@ -1087,15 +1109,16 @@ static bool is_dsc_need_re_compute(
> > >     return is_dsc_need_re_compute;
> > >  }
> > >
> > > -bool compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> > > -                                  struct dc_state *dc_state,
> > > -                                  struct dsc_mst_fairness_vars *vars)
> > > +int compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> > > +                                 struct dc_state *dc_state,
> > > +                                 struct dsc_mst_fairness_vars *vars)
> > >  {
> > >     int i, j;
> > >     struct dc_stream_state *stream;
> > >     bool computed_streams[MAX_PIPES];
> > >     struct amdgpu_dm_connector *aconnector;
> > >     int link_vars_start_index = 0;
> > > +   int ret = 0;
> > >
> > >     for (i = 0; i < dc_state->stream_count; i++)
> > >             computed_streams[i] = false;
> > > @@ -1118,17 +1141,19 @@ bool compute_mst_dsc_configs_for_state(struct
> > > drm_atomic_state *state,
> > >                     continue;
> > >
> > >             if (dcn20_remove_stream_from_ctx(stream->ctx->dc,
> > > dc_state, stream) != DC_OK)
> > > -                   return false;
> > > +                   return -EINVAL;
> > >
> > >             if (!is_dsc_need_re_compute(state, dc_state, stream->link))
> > >                     continue;
> > >
> > >             mutex_lock(&aconnector->mst_mgr.lock);
> > > -           if (!compute_mst_dsc_configs_for_link(state, dc_state,
> > > stream->link, vars,
> > > -                                                 &aconnector->mst_mgr,
> > > -                                                 &link_vars_start_index)) {
> > > +
> > > +           ret = compute_mst_dsc_configs_for_link(state, dc_state,
> > > stream->link, vars,
> > > +                                                  &aconnector->mst_mgr,
> > > +                                                  &link_vars_start_index);
> > > +           if (ret != 0) {
> > >                     mutex_unlock(&aconnector->mst_mgr.lock);
> > > -                   return false;
> > > +                   return ret;
> > >             }
> > >             mutex_unlock(&aconnector->mst_mgr.lock);
> > >
> > > @@ -1143,22 +1168,22 @@ bool compute_mst_dsc_configs_for_state(struct
> > > drm_atomic_state *state,
> > >
> > >             if (stream->timing.flags.DSC == 1)
> > >                     if (dc_stream_add_dsc_to_resource(stream->ctx-
> > > > dc, dc_state, stream) != DC_OK)
> > > -                           return false;
> > > +                           return -EINVAL;
> > >     }
> > >
> > > -   return true;
> > > +   return ret;
> > >  }
> > >
> > > -static bool
> > > -   pre_compute_mst_dsc_configs_for_state(struct drm_atomic_state
> > > *state,
> > > -                                         struct dc_state *dc_state,
> > > -                                         struct dsc_mst_fairness_vars
> > > *vars)
> > > +static int pre_compute_mst_dsc_configs_for_state(struct
> > > drm_atomic_state *state,
> > > +                                            struct dc_state *dc_state,
> > > +                                            struct dsc_mst_fairness_vars
> > > *vars)
> > >  {
> > >     int i, j;
> > >     struct dc_stream_state *stream;
> > >     bool computed_streams[MAX_PIPES];
> > >     struct amdgpu_dm_connector *aconnector;
> > >     int link_vars_start_index = 0;
> > > +   int ret;
> > >
> > >     for (i = 0; i < dc_state->stream_count; i++)
> > >             computed_streams[i] = false;
> > > @@ -1184,11 +1209,12 @@ static bool
> > >                     continue;
> > >
> > >             mutex_lock(&aconnector->mst_mgr.lock);
> > > -           if (!compute_mst_dsc_configs_for_link(state, dc_state,
> > > stream->link, vars,
> > > -                                                 &aconnector->mst_mgr,
> > > -                                                 &link_vars_start_index)) {
> > > +           ret = compute_mst_dsc_configs_for_link(state, dc_state,
> > > stream->link, vars,
> > > +                                                  &aconnector->mst_mgr,
> > > +                                                  &link_vars_start_index);
> > > +           if (ret != 0) {
> > >                     mutex_unlock(&aconnector->mst_mgr.lock);
> > > -                   return false;
> > > +                   return ret;
> > >             }
> > >             mutex_unlock(&aconnector->mst_mgr.lock);
> > >
> > > @@ -1198,7 +1224,7 @@ static bool
> > >             }
> > >     }
> > >
> > > -   return true;
> > > +   return ret;
> > >  }
> > >
> > >  static int find_crtc_index_in_state_by_stream(struct drm_atomic_state
> > > *state, @@ -1253,9 +1279,9 @@ static bool
> > > is_dsc_precompute_needed(struct drm_atomic_state *state)
> > >     return ret;
> > >  }
> > >
> > > -bool pre_validate_dsc(struct drm_atomic_state *state,
> > > -                 struct dm_atomic_state **dm_state_ptr,
> > > -                 struct dsc_mst_fairness_vars *vars)
> > > +int pre_validate_dsc(struct drm_atomic_state *state,
> > > +                struct dm_atomic_state **dm_state_ptr,
> > > +                struct dsc_mst_fairness_vars *vars)
> > >  {
> > >     int i;
> > >     struct dm_atomic_state *dm_state;
> > > @@ -1264,11 +1290,12 @@ bool pre_validate_dsc(struct drm_atomic_state
> > > *state,
> > >
> > >     if (!is_dsc_precompute_needed(state)) {
> > >             DRM_INFO_ONCE("DSC precompute is not needed.\n");
> > > -           return true;
> > > +           return 0;
> > >     }
> > > -   if (dm_atomic_get_state(state, dm_state_ptr)) {
> > > +   ret = dm_atomic_get_state(state, dm_state_ptr);
> > > +   if (ret != 0) {
> > >             DRM_INFO_ONCE("dm_atomic_get_state() failed\n");
> > > -           return false;
> > > +           return ret;
> > >     }
> > >     dm_state = *dm_state_ptr;
> > >
> > > @@ -1280,7 +1307,7 @@ bool pre_validate_dsc(struct drm_atomic_state
> > > *state,
> > >
> > >     local_dc_state = kmemdup(dm_state->context, sizeof(struct
> > > dc_state), GFP_KERNEL);
> > >     if (!local_dc_state)
> > > -           return false;
> > > +           return -ENOMEM;
> > >
> > >     for (i = 0; i < local_dc_state->stream_count; i++) {
> > >             struct dc_stream_state *stream = dm_state->context-
> > > > streams[i]; @@ -1316,9 +1343,9 @@ bool pre_validate_dsc(struct
> > > drm_atomic_state *state,
> > >     if (ret != 0)
> > >             goto clean_exit;
> > >
> > > -   if (!pre_compute_mst_dsc_configs_for_state(state, local_dc_state,
> > > vars)) {
> > > +   ret = pre_compute_mst_dsc_configs_for_state(state, local_dc_state,
> > > vars);
> > > +   if (ret != 0) {
> > >
> > >     DRM_INFO_ONCE("pre_compute_mst_dsc_configs_for_state()
> > > failed\n");
> > > -           ret = -EINVAL;
> > >             goto clean_exit;
> > >     }
> > >
> > > @@ -1349,7 +1376,7 @@ bool pre_validate_dsc(struct drm_atomic_state
> > > *state,
> > >
> > >     kfree(local_dc_state);
> > >
> > > -   return (ret == 0);
> > > +   return ret;
> > >  }
> > >
> > >  static unsigned int kbps_from_pbn(unsigned int pbn) diff --git
> > > a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> > > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> > > index b92a7c5671aa2..97fd70df531bf 100644
> > > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> > > +++
> > > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> > > @@ -53,15 +53,15 @@ struct dsc_mst_fairness_vars {
> > >     struct amdgpu_dm_connector *aconnector;  };
> > >
> > > -bool compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> > > -                                  struct dc_state *dc_state,
> > > -                                  struct dsc_mst_fairness_vars *vars);
> > > +int compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> > > +                                 struct dc_state *dc_state,
> > > +                                 struct dsc_mst_fairness_vars *vars);
> > >
> > >  bool needs_dsc_aux_workaround(struct dc_link *link);
> > >
> > > -bool pre_validate_dsc(struct drm_atomic_state *state,
> > > -                 struct dm_atomic_state **dm_state_ptr,
> > > -                 struct dsc_mst_fairness_vars *vars);
> > > +int pre_validate_dsc(struct drm_atomic_state *state,
> > > +                struct dm_atomic_state **dm_state_ptr,
> > > +                struct dsc_mst_fairness_vars *vars);
> > >
> > >  enum dc_status dm_dp_mst_is_port_support_mode(
> > >     struct amdgpu_dm_connector *aconnector,
> > > --
> > > 2.37.3
> >
>
> --
> Cheers,
>  Lyude Paul (she/her)
>  Software Engineer at Red Hat
>
  

of course, will do in just a moment

On Fri, 2022-11-18 at 14:46 -0500, Alex Deucher wrote:
> I've already picked this up.  Can you send a follow up patch with just
> the coverity fix?
> 
> Alex
> 
> On Fri, Nov 18, 2022 at 2:17 PM Lyude Paul <lyude@redhat.com> wrote:
> > 
> > JFYI, Coverity pointed out one more issue with this series so I'm going to
> > send out a respin real quick to fix it. It's just a missing variable
> > assignment (we leave ret unassigned by mistake in
> > pre_compute_mst_dsc_configs()) so I will carry over your r-b on it.
> > 
> > On Wed, 2022-11-16 at 04:39 +0000, Lin, Wayne wrote:
> > > [Public]
> > > 
> > > All the patch set looks good to me. Feel free to add:
> > > Reviewed-by: Wayne Lin <Wayne.Lin@amd.com>
> > > 
> > > Again, thank you Lyude for helping on this!!!
> > > 
> > > Regards,
> > > Wayne
> > > > -----Original Message-----
> > > > From: Lyude Paul <lyude@redhat.com>
> > > > Sent: Tuesday, November 15, 2022 6:18 AM
> > > > To: amd-gfx@lists.freedesktop.org
> > > > Cc: Wentland, Harry <Harry.Wentland@amd.com>; stable@vger.kernel.org;
> > > > Li, Sun peng (Leo) <Sunpeng.Li@amd.com>; Siqueira, Rodrigo
> > > > <Rodrigo.Siqueira@amd.com>; Deucher, Alexander
> > > > <Alexander.Deucher@amd.com>; Koenig, Christian
> > > > <Christian.Koenig@amd.com>; Pan, Xinhui <Xinhui.Pan@amd.com>; David
> > > > Airlie <airlied@gmail.com>; Daniel Vetter <daniel@ffwll.ch>; Kazlauskas,
> > > > Nicholas <Nicholas.Kazlauskas@amd.com>; Pillai, Aurabindo
> > > > <Aurabindo.Pillai@amd.com>; Li, Roman <Roman.Li@amd.com>; Zuo, Jerry
> > > > <Jerry.Zuo@amd.com>; Wu, Hersen <hersenxs.wu@amd.com>; Lin, Wayne
> > > > <Wayne.Lin@amd.com>; Thomas Zimmermann <tzimmermann@suse.de>;
> > > > Mahfooz, Hamza <Hamza.Mahfooz@amd.com>; Hung, Alex
> > > > <Alex.Hung@amd.com>; Mikita Lipski <mikita.lipski@amd.com>; Liu,
> > > > Wenjing <Wenjing.Liu@amd.com>; Francis, David
> > > > <David.Francis@amd.com>; open list:DRM DRIVERS <dri-
> > > > devel@lists.freedesktop.org>; open list <linux-kernel@vger.kernel.org>
> > > > Subject: [PATCH v2 1/4] drm/amdgpu/mst: Stop ignoring error codes and
> > > > deadlocking
> > > > 
> > > > It appears that amdgpu makes the mistake of completely ignoring the return
> > > > values from the DP MST helpers, and instead just returns a simple true/false.
> > > > In this case, it seems to have come back to bite us because as a result of
> > > > simply returning false from compute_mst_dsc_configs_for_state(), amdgpu
> > > > had no way of telling when a deadlock happened from these helpers. This
> > > > could definitely result in some kernel splats.
> > > > 
> > > > V2:
> > > > * Address Wayne's comments (fix another bunch of spots where we weren't
> > > >   passing down return codes)
> > > > 
> > > > Signed-off-by: Lyude Paul <lyude@redhat.com>
> > > > Fixes: 8c20a1ed9b4f ("drm/amd/display: MST DSC compute fair share")
> > > > Cc: Harry Wentland <harry.wentland@amd.com>
> > > > Cc: <stable@vger.kernel.org> # v5.6+
> > > > ---
> > > >  .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |  18 +-
> > > >  .../display/amdgpu_dm/amdgpu_dm_mst_types.c   | 235 ++++++++++------
> > > > --
> > > >  .../display/amdgpu_dm/amdgpu_dm_mst_types.h   |  12 +-
> > > >  3 files changed, 147 insertions(+), 118 deletions(-)
> > > > 
> > > > diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > > > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > > > index 0db2a88cd4d7b..852a2100c6b38 100644
> > > > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > > > +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > > > @@ -6462,7 +6462,7 @@ static int
> > > > dm_update_mst_vcpi_slots_for_dsc(struct drm_atomic_state *state,
> > > >     struct drm_connector_state *new_con_state;
> > > >     struct amdgpu_dm_connector *aconnector;
> > > >     struct dm_connector_state *dm_conn_state;
> > > > -   int i, j;
> > > > +   int i, j, ret;
> > > >     int vcpi, pbn_div, pbn, slot_num = 0;
> > > > 
> > > >     for_each_new_connector_in_state(state, connector,
> > > > new_con_state, i) { @@ -6509,8 +6509,11 @@ static int
> > > > dm_update_mst_vcpi_slots_for_dsc(struct drm_atomic_state *state,
> > > >                     dm_conn_state->pbn = pbn;
> > > >                     dm_conn_state->vcpi_slots = slot_num;
> > > > 
> > > > -                   drm_dp_mst_atomic_enable_dsc(state, aconnector-
> > > > > port, dm_conn_state->pbn,
> > > > -                                                false);
> > > > +                   ret = drm_dp_mst_atomic_enable_dsc(state,
> > > > aconnector->port,
> > > > +                                                      dm_conn_state-
> > > > > pbn, false);
> > > > +                   if (ret < 0)
> > > > +                           return ret;
> > > > +
> > > >                     continue;
> > > >             }
> > > > 
> > > > @@ -9523,10 +9526,9 @@ static int amdgpu_dm_atomic_check(struct
> > > > drm_device *dev,
> > > > 
> > > >  #if defined(CONFIG_DRM_AMD_DC_DCN)
> > > >     if (dc_resource_is_dsc_encoding_supported(dc)) {
> > > > -           if (!pre_validate_dsc(state, &dm_state, vars)) {
> > > > -                   ret = -EINVAL;
> > > > +           ret = pre_validate_dsc(state, &dm_state, vars);
> > > > +           if (ret != 0)
> > > >                     goto fail;
> > > > -           }
> > > >     }
> > > >  #endif
> > > > 
> > > > @@ -9621,9 +9623,9 @@ static int amdgpu_dm_atomic_check(struct
> > > > drm_device *dev,
> > > >             }
> > > > 
> > > >  #if defined(CONFIG_DRM_AMD_DC_DCN)
> > > > -           if (!compute_mst_dsc_configs_for_state(state, dm_state-
> > > > > context, vars)) {
> > > > +           ret = compute_mst_dsc_configs_for_state(state, dm_state-
> > > > > context, vars);
> > > > +           if (ret) {
> > > > 
> > > >     DRM_DEBUG_DRIVER("compute_mst_dsc_configs_for_state()
> > > > failed\n");
> > > > -                   ret = -EINVAL;
> > > >                     goto fail;
> > > >             }
> > > > 
> > > > diff --git
> > > > a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > > > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > > > index 6ff96b4bdda5c..bba2e8aaa2c20 100644
> > > > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > > > +++
> > > > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > > > @@ -703,13 +703,13 @@ static int bpp_x16_from_pbn(struct
> > > > dsc_mst_fairness_params param, int pbn)
> > > >     return dsc_config.bits_per_pixel;
> > > >  }
> > > > 
> > > > -static bool increase_dsc_bpp(struct drm_atomic_state *state,
> > > > -                        struct drm_dp_mst_topology_state *mst_state,
> > > > -                        struct dc_link *dc_link,
> > > > -                        struct dsc_mst_fairness_params *params,
> > > > -                        struct dsc_mst_fairness_vars *vars,
> > > > -                        int count,
> > > > -                        int k)
> > > > +static int increase_dsc_bpp(struct drm_atomic_state *state,
> > > > +                       struct drm_dp_mst_topology_state *mst_state,
> > > > +                       struct dc_link *dc_link,
> > > > +                       struct dsc_mst_fairness_params *params,
> > > > +                       struct dsc_mst_fairness_vars *vars,
> > > > +                       int count,
> > > > +                       int k)
> > > >  {
> > > >     int i;
> > > >     bool bpp_increased[MAX_PIPES];
> > > > @@ -719,6 +719,7 @@ static bool increase_dsc_bpp(struct
> > > > drm_atomic_state *state,
> > > >     int remaining_to_increase = 0;
> > > >     int link_timeslots_used;
> > > >     int fair_pbn_alloc;
> > > > +   int ret = 0;
> > > > 
> > > >     for (i = 0; i < count; i++) {
> > > >             if (vars[i + k].dsc_enabled) {
> > > > @@ -757,52 +758,60 @@ static bool increase_dsc_bpp(struct
> > > > drm_atomic_state *state,
> > > > 
> > > >             if (initial_slack[next_index] > fair_pbn_alloc) {
> > > >                     vars[next_index].pbn += fair_pbn_alloc;
> > > > -                   if (drm_dp_atomic_find_time_slots(state,
> > > > -
> > > > params[next_index].port->mgr,
> > > > -
> > > > params[next_index].port,
> > > > -
> > > > vars[next_index].pbn) < 0)
> > > > -                           return false;
> > > > -                   if (!drm_dp_mst_atomic_check(state)) {
> > > > +                   ret = drm_dp_atomic_find_time_slots(state,
> > > > +
> > > > params[next_index].port->mgr,
> > > > +
> > > > params[next_index].port,
> > > > +
> > > > vars[next_index].pbn);
> > > > +                   if (ret < 0)
> > > > +                           return ret;
> > > > +
> > > > +                   ret = drm_dp_mst_atomic_check(state);
> > > > +                   if (ret == 0) {
> > > >                             vars[next_index].bpp_x16 =
> > > > bpp_x16_from_pbn(params[next_index], vars[next_index].pbn);
> > > >                     } else {
> > > >                             vars[next_index].pbn -= fair_pbn_alloc;
> > > > -                           if (drm_dp_atomic_find_time_slots(state,
> > > > -
> > > > params[next_index].port->mgr,
> > > > -
> > > > params[next_index].port,
> > > > -
> > > > vars[next_index].pbn) < 0)
> > > > -                                   return false;
> > > > +                           ret = drm_dp_atomic_find_time_slots(state,
> > > > +
> > > > params[next_index].port->mgr,
> > > > +
> > > > params[next_index].port,
> > > > +
> > > > vars[next_index].pbn);
> > > > +                           if (ret < 0)
> > > > +                                   return ret;
> > > >                     }
> > > >             } else {
> > > >                     vars[next_index].pbn += initial_slack[next_index];
> > > > -                   if (drm_dp_atomic_find_time_slots(state,
> > > > -
> > > > params[next_index].port->mgr,
> > > > -
> > > > params[next_index].port,
> > > > -
> > > > vars[next_index].pbn) < 0)
> > > > -                           return false;
> > > > -                   if (!drm_dp_mst_atomic_check(state)) {
> > > > +                   ret = drm_dp_atomic_find_time_slots(state,
> > > > +
> > > > params[next_index].port->mgr,
> > > > +
> > > > params[next_index].port,
> > > > +
> > > > vars[next_index].pbn);
> > > > +                   if (ret < 0)
> > > > +                           return ret;
> > > > +
> > > > +                   ret = drm_dp_mst_atomic_check(state);
> > > > +                   if (ret == 0) {
> > > >                             vars[next_index].bpp_x16 =
> > > > params[next_index].bw_range.max_target_bpp_x16;
> > > >                     } else {
> > > >                             vars[next_index].pbn -=
> > > > initial_slack[next_index];
> > > > -                           if (drm_dp_atomic_find_time_slots(state,
> > > > -
> > > > params[next_index].port->mgr,
> > > > -
> > > > params[next_index].port,
> > > > -
> > > > vars[next_index].pbn) < 0)
> > > > -                                   return false;
> > > > +                           ret = drm_dp_atomic_find_time_slots(state,
> > > > +
> > > > params[next_index].port->mgr,
> > > > +
> > > > params[next_index].port,
> > > > +
> > > > vars[next_index].pbn);
> > > > +                           if (ret < 0)
> > > > +                                   return ret;
> > > >                     }
> > > >             }
> > > > 
> > > >             bpp_increased[next_index] = true;
> > > >             remaining_to_increase--;
> > > >     }
> > > > -   return true;
> > > > +   return 0;
> > > >  }
> > > > 
> > > > -static bool try_disable_dsc(struct drm_atomic_state *state,
> > > > -                       struct dc_link *dc_link,
> > > > -                       struct dsc_mst_fairness_params *params,
> > > > -                       struct dsc_mst_fairness_vars *vars,
> > > > -                       int count,
> > > > -                       int k)
> > > > +static int try_disable_dsc(struct drm_atomic_state *state,
> > > > +                      struct dc_link *dc_link,
> > > > +                      struct dsc_mst_fairness_params *params,
> > > > +                      struct dsc_mst_fairness_vars *vars,
> > > > +                      int count,
> > > > +                      int k)
> > > >  {
> > > >     int i;
> > > >     bool tried[MAX_PIPES];
> > > > @@ -810,6 +819,7 @@ static bool try_disable_dsc(struct drm_atomic_state
> > > > *state,
> > > >     int max_kbps_increase;
> > > >     int next_index;
> > > >     int remaining_to_try = 0;
> > > > +   int ret;
> > > > 
> > > >     for (i = 0; i < count; i++) {
> > > >             if (vars[i + k].dsc_enabled
> > > > @@ -840,49 +850,52 @@ static bool try_disable_dsc(struct
> > > > drm_atomic_state *state,
> > > >                     break;
> > > > 
> > > >             vars[next_index].pbn =
> > > > kbps_to_peak_pbn(params[next_index].bw_range.stream_kbps);
> > > > -           if (drm_dp_atomic_find_time_slots(state,
> > > > -                                             params[next_index].port-
> > > > > mgr,
> > > > -                                             params[next_index].port,
> > > > -                                             vars[next_index].pbn) < 0)
> > > > -                   return false;
> > > > +           ret = drm_dp_atomic_find_time_slots(state,
> > > > +                                               params[next_index].port-
> > > > > mgr,
> > > > +                                               params[next_index].port,
> > > > +                                               vars[next_index].pbn);
> > > > +           if (ret < 0)
> > > > +                   return ret;
> > > > 
> > > > -           if (!drm_dp_mst_atomic_check(state)) {
> > > > +           ret = drm_dp_mst_atomic_check(state);
> > > > +           if (ret == 0) {
> > > >                     vars[next_index].dsc_enabled = false;
> > > >                     vars[next_index].bpp_x16 = 0;
> > > >             } else {
> > > >                     vars[next_index].pbn =
> > > > kbps_to_peak_pbn(params[next_index].bw_range.max_kbps);
> > > > -                   if (drm_dp_atomic_find_time_slots(state,
> > > > -
> > > > params[next_index].port->mgr,
> > > > -
> > > > params[next_index].port,
> > > > -
> > > > vars[next_index].pbn) < 0)
> > > > -                           return false;
> > > > +                   ret = drm_dp_atomic_find_time_slots(state,
> > > > +
> > > > params[next_index].port->mgr,
> > > > +
> > > > params[next_index].port,
> > > > +
> > > > vars[next_index].pbn);
> > > > +                   if (ret < 0)
> > > > +                           return ret;
> > > >             }
> > > > 
> > > >             tried[next_index] = true;
> > > >             remaining_to_try--;
> > > >     }
> > > > -   return true;
> > > > +   return 0;
> > > >  }
> > > > 
> > > > -static bool compute_mst_dsc_configs_for_link(struct drm_atomic_state
> > > > *state,
> > > > -                                        struct dc_state *dc_state,
> > > > -                                        struct dc_link *dc_link,
> > > > -                                        struct dsc_mst_fairness_vars *vars,
> > > > -                                        struct drm_dp_mst_topology_mgr
> > > > *mgr,
> > > > -                                        int *link_vars_start_index)
> > > > +static int compute_mst_dsc_configs_for_link(struct drm_atomic_state
> > > > *state,
> > > > +                                       struct dc_state *dc_state,
> > > > +                                       struct dc_link *dc_link,
> > > > +                                       struct dsc_mst_fairness_vars *vars,
> > > > +                                       struct drm_dp_mst_topology_mgr
> > > > *mgr,
> > > > +                                       int *link_vars_start_index)
> > > >  {
> > > >     struct dc_stream_state *stream;
> > > >     struct dsc_mst_fairness_params params[MAX_PIPES];
> > > >     struct amdgpu_dm_connector *aconnector;
> > > >     struct drm_dp_mst_topology_state *mst_state =
> > > > drm_atomic_get_mst_topology_state(state, mgr);
> > > >     int count = 0;
> > > > -   int i, k;
> > > > +   int i, k, ret;
> > > >     bool debugfs_overwrite = false;
> > > > 
> > > >     memset(params, 0, sizeof(params));
> > > > 
> > > >     if (IS_ERR(mst_state))
> > > > -           return false;
> > > > +           return PTR_ERR(mst_state);
> > > > 
> > > >     mst_state->pbn_div = dm_mst_get_pbn_divider(dc_link);  #if
> > > > defined(CONFIG_DRM_AMD_DC_DCN) @@ -933,7 +946,7 @@ static bool
> > > > compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,
> > > > 
> > > >     if (count == 0) {
> > > >             ASSERT(0);
> > > > -           return true;
> > > > +           return 0;
> > > >     }
> > > > 
> > > >     /* k is start index of vars for current phy link used by mst hub */ @@
> > > > -947,13 +960,17 @@ static bool compute_mst_dsc_configs_for_link(struct
> > > > drm_atomic_state *state,
> > > >             vars[i + k].pbn =
> > > > kbps_to_peak_pbn(params[i].bw_range.stream_kbps);
> > > >             vars[i + k].dsc_enabled = false;
> > > >             vars[i + k].bpp_x16 = 0;
> > > > -           if (drm_dp_atomic_find_time_slots(state, params[i].port-
> > > > > mgr, params[i].port,
> > > > -                                             vars[i + k].pbn) < 0)
> > > > -                   return false;
> > > > +           ret = drm_dp_atomic_find_time_slots(state, params[i].port-
> > > > > mgr, params[i].port,
> > > > +                                               vars[i + k].pbn);
> > > > +           if (ret < 0)
> > > > +                   return ret;
> > > >     }
> > > > -   if (!drm_dp_mst_atomic_check(state) && !debugfs_overwrite) {
> > > > +   ret = drm_dp_mst_atomic_check(state);
> > > > +   if (ret == 0 && !debugfs_overwrite) {
> > > >             set_dsc_configs_from_fairness_vars(params, vars, count, k);
> > > > -           return true;
> > > > +           return 0;
> > > > +   } else if (ret != -ENOSPC) {
> > > > +           return ret;
> > > >     }
> > > > 
> > > >     /* Try max compression */
> > > > @@ -962,31 +979,36 @@ static bool
> > > > compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,
> > > >                     vars[i + k].pbn =
> > > > kbps_to_peak_pbn(params[i].bw_range.min_kbps);
> > > >                     vars[i + k].dsc_enabled = true;
> > > >                     vars[i + k].bpp_x16 =
> > > > params[i].bw_range.min_target_bpp_x16;
> > > > -                   if (drm_dp_atomic_find_time_slots(state,
> > > > params[i].port->mgr,
> > > > -                                                     params[i].port, vars[i
> > > > + k].pbn) < 0)
> > > > -                           return false;
> > > > +                   ret = drm_dp_atomic_find_time_slots(state,
> > > > params[i].port->mgr,
> > > > +                                                       params[i].port,
> > > > vars[i + k].pbn);
> > > > +                   if (ret < 0)
> > > > +                           return ret;
> > > >             } else {
> > > >                     vars[i + k].pbn =
> > > > kbps_to_peak_pbn(params[i].bw_range.stream_kbps);
> > > >                     vars[i + k].dsc_enabled = false;
> > > >                     vars[i + k].bpp_x16 = 0;
> > > > -                   if (drm_dp_atomic_find_time_slots(state,
> > > > params[i].port->mgr,
> > > > -                                                     params[i].port, vars[i
> > > > + k].pbn) < 0)
> > > > -                           return false;
> > > > +                   ret = drm_dp_atomic_find_time_slots(state,
> > > > params[i].port->mgr,
> > > > +                                                       params[i].port,
> > > > vars[i + k].pbn);
> > > > +                   if (ret < 0)
> > > > +                           return ret;
> > > >             }
> > > >     }
> > > > -   if (drm_dp_mst_atomic_check(state))
> > > > -           return false;
> > > > +   ret = drm_dp_mst_atomic_check(state);
> > > > +   if (ret != 0)
> > > > +           return ret;
> > > > 
> > > >     /* Optimize degree of compression */
> > > > -   if (!increase_dsc_bpp(state, mst_state, dc_link, params, vars, count,
> > > > k))
> > > > -           return false;
> > > > +   ret = increase_dsc_bpp(state, mst_state, dc_link, params, vars,
> > > > count, k);
> > > > +   if (ret < 0)
> > > > +           return ret;
> > > > 
> > > > -   if (!try_disable_dsc(state, dc_link, params, vars, count, k))
> > > > -           return false;
> > > > +   ret = try_disable_dsc(state, dc_link, params, vars, count, k);
> > > > +   if (ret < 0)
> > > > +           return ret;
> > > > 
> > > >     set_dsc_configs_from_fairness_vars(params, vars, count, k);
> > > > 
> > > > -   return true;
> > > > +   return 0;
> > > >  }
> > > > 
> > > >  static bool is_dsc_need_re_compute(
> > > > @@ -1087,15 +1109,16 @@ static bool is_dsc_need_re_compute(
> > > >     return is_dsc_need_re_compute;
> > > >  }
> > > > 
> > > > -bool compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> > > > -                                  struct dc_state *dc_state,
> > > > -                                  struct dsc_mst_fairness_vars *vars)
> > > > +int compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> > > > +                                 struct dc_state *dc_state,
> > > > +                                 struct dsc_mst_fairness_vars *vars)
> > > >  {
> > > >     int i, j;
> > > >     struct dc_stream_state *stream;
> > > >     bool computed_streams[MAX_PIPES];
> > > >     struct amdgpu_dm_connector *aconnector;
> > > >     int link_vars_start_index = 0;
> > > > +   int ret = 0;
> > > > 
> > > >     for (i = 0; i < dc_state->stream_count; i++)
> > > >             computed_streams[i] = false;
> > > > @@ -1118,17 +1141,19 @@ bool compute_mst_dsc_configs_for_state(struct
> > > > drm_atomic_state *state,
> > > >                     continue;
> > > > 
> > > >             if (dcn20_remove_stream_from_ctx(stream->ctx->dc,
> > > > dc_state, stream) != DC_OK)
> > > > -                   return false;
> > > > +                   return -EINVAL;
> > > > 
> > > >             if (!is_dsc_need_re_compute(state, dc_state, stream->link))
> > > >                     continue;
> > > > 
> > > >             mutex_lock(&aconnector->mst_mgr.lock);
> > > > -           if (!compute_mst_dsc_configs_for_link(state, dc_state,
> > > > stream->link, vars,
> > > > -                                                 &aconnector->mst_mgr,
> > > > -                                                 &link_vars_start_index)) {
> > > > +
> > > > +           ret = compute_mst_dsc_configs_for_link(state, dc_state,
> > > > stream->link, vars,
> > > > +                                                  &aconnector->mst_mgr,
> > > > +                                                  &link_vars_start_index);
> > > > +           if (ret != 0) {
> > > >                     mutex_unlock(&aconnector->mst_mgr.lock);
> > > > -                   return false;
> > > > +                   return ret;
> > > >             }
> > > >             mutex_unlock(&aconnector->mst_mgr.lock);
> > > > 
> > > > @@ -1143,22 +1168,22 @@ bool compute_mst_dsc_configs_for_state(struct
> > > > drm_atomic_state *state,
> > > > 
> > > >             if (stream->timing.flags.DSC == 1)
> > > >                     if (dc_stream_add_dsc_to_resource(stream->ctx-
> > > > > dc, dc_state, stream) != DC_OK)
> > > > -                           return false;
> > > > +                           return -EINVAL;
> > > >     }
> > > > 
> > > > -   return true;
> > > > +   return ret;
> > > >  }
> > > > 
> > > > -static bool
> > > > -   pre_compute_mst_dsc_configs_for_state(struct drm_atomic_state
> > > > *state,
> > > > -                                         struct dc_state *dc_state,
> > > > -                                         struct dsc_mst_fairness_vars
> > > > *vars)
> > > > +static int pre_compute_mst_dsc_configs_for_state(struct
> > > > drm_atomic_state *state,
> > > > +                                            struct dc_state *dc_state,
> > > > +                                            struct dsc_mst_fairness_vars
> > > > *vars)
> > > >  {
> > > >     int i, j;
> > > >     struct dc_stream_state *stream;
> > > >     bool computed_streams[MAX_PIPES];
> > > >     struct amdgpu_dm_connector *aconnector;
> > > >     int link_vars_start_index = 0;
> > > > +   int ret;
> > > > 
> > > >     for (i = 0; i < dc_state->stream_count; i++)
> > > >             computed_streams[i] = false;
> > > > @@ -1184,11 +1209,12 @@ static bool
> > > >                     continue;
> > > > 
> > > >             mutex_lock(&aconnector->mst_mgr.lock);
> > > > -           if (!compute_mst_dsc_configs_for_link(state, dc_state,
> > > > stream->link, vars,
> > > > -                                                 &aconnector->mst_mgr,
> > > > -                                                 &link_vars_start_index)) {
> > > > +           ret = compute_mst_dsc_configs_for_link(state, dc_state,
> > > > stream->link, vars,
> > > > +                                                  &aconnector->mst_mgr,
> > > > +                                                  &link_vars_start_index);
> > > > +           if (ret != 0) {
> > > >                     mutex_unlock(&aconnector->mst_mgr.lock);
> > > > -                   return false;
> > > > +                   return ret;
> > > >             }
> > > >             mutex_unlock(&aconnector->mst_mgr.lock);
> > > > 
> > > > @@ -1198,7 +1224,7 @@ static bool
> > > >             }
> > > >     }
> > > > 
> > > > -   return true;
> > > > +   return ret;
> > > >  }
> > > > 
> > > >  static int find_crtc_index_in_state_by_stream(struct drm_atomic_state
> > > > *state, @@ -1253,9 +1279,9 @@ static bool
> > > > is_dsc_precompute_needed(struct drm_atomic_state *state)
> > > >     return ret;
> > > >  }
> > > > 
> > > > -bool pre_validate_dsc(struct drm_atomic_state *state,
> > > > -                 struct dm_atomic_state **dm_state_ptr,
> > > > -                 struct dsc_mst_fairness_vars *vars)
> > > > +int pre_validate_dsc(struct drm_atomic_state *state,
> > > > +                struct dm_atomic_state **dm_state_ptr,
> > > > +                struct dsc_mst_fairness_vars *vars)
> > > >  {
> > > >     int i;
> > > >     struct dm_atomic_state *dm_state;
> > > > @@ -1264,11 +1290,12 @@ bool pre_validate_dsc(struct drm_atomic_state
> > > > *state,
> > > > 
> > > >     if (!is_dsc_precompute_needed(state)) {
> > > >             DRM_INFO_ONCE("DSC precompute is not needed.\n");
> > > > -           return true;
> > > > +           return 0;
> > > >     }
> > > > -   if (dm_atomic_get_state(state, dm_state_ptr)) {
> > > > +   ret = dm_atomic_get_state(state, dm_state_ptr);
> > > > +   if (ret != 0) {
> > > >             DRM_INFO_ONCE("dm_atomic_get_state() failed\n");
> > > > -           return false;
> > > > +           return ret;
> > > >     }
> > > >     dm_state = *dm_state_ptr;
> > > > 
> > > > @@ -1280,7 +1307,7 @@ bool pre_validate_dsc(struct drm_atomic_state
> > > > *state,
> > > > 
> > > >     local_dc_state = kmemdup(dm_state->context, sizeof(struct
> > > > dc_state), GFP_KERNEL);
> > > >     if (!local_dc_state)
> > > > -           return false;
> > > > +           return -ENOMEM;
> > > > 
> > > >     for (i = 0; i < local_dc_state->stream_count; i++) {
> > > >             struct dc_stream_state *stream = dm_state->context-
> > > > > streams[i]; @@ -1316,9 +1343,9 @@ bool pre_validate_dsc(struct
> > > > drm_atomic_state *state,
> > > >     if (ret != 0)
> > > >             goto clean_exit;
> > > > 
> > > > -   if (!pre_compute_mst_dsc_configs_for_state(state, local_dc_state,
> > > > vars)) {
> > > > +   ret = pre_compute_mst_dsc_configs_for_state(state, local_dc_state,
> > > > vars);
> > > > +   if (ret != 0) {
> > > > 
> > > >     DRM_INFO_ONCE("pre_compute_mst_dsc_configs_for_state()
> > > > failed\n");
> > > > -           ret = -EINVAL;
> > > >             goto clean_exit;
> > > >     }
> > > > 
> > > > @@ -1349,7 +1376,7 @@ bool pre_validate_dsc(struct drm_atomic_state
> > > > *state,
> > > > 
> > > >     kfree(local_dc_state);
> > > > 
> > > > -   return (ret == 0);
> > > > +   return ret;
> > > >  }
> > > > 
> > > >  static unsigned int kbps_from_pbn(unsigned int pbn) diff --git
> > > > a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> > > > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> > > > index b92a7c5671aa2..97fd70df531bf 100644
> > > > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> > > > +++
> > > > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> > > > @@ -53,15 +53,15 @@ struct dsc_mst_fairness_vars {
> > > >     struct amdgpu_dm_connector *aconnector;  };
> > > > 
> > > > -bool compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> > > > -                                  struct dc_state *dc_state,
> > > > -                                  struct dsc_mst_fairness_vars *vars);
> > > > +int compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> > > > +                                 struct dc_state *dc_state,
> > > > +                                 struct dsc_mst_fairness_vars *vars);
> > > > 
> > > >  bool needs_dsc_aux_workaround(struct dc_link *link);
> > > > 
> > > > -bool pre_validate_dsc(struct drm_atomic_state *state,
> > > > -                 struct dm_atomic_state **dm_state_ptr,
> > > > -                 struct dsc_mst_fairness_vars *vars);
> > > > +int pre_validate_dsc(struct drm_atomic_state *state,
> > > > +                struct dm_atomic_state **dm_state_ptr,
> > > > +                struct dsc_mst_fairness_vars *vars);
> > > > 
> > > >  enum dc_status dm_dp_mst_is_port_support_mode(
> > > >     struct amdgpu_dm_connector *aconnector,
> > > > --
> > > > 2.37.3
> > > 
> > 
> > --
> > Cheers,
> >  Lyude Paul (she/her)
> >  Software Engineer at Red Hat
> > 
>
  

JFYI - I'm not sure of the correct commit ID to add for the Fixes: tag since
it's in your branch, so I'll omit that and let you add it into the patch

On Fri, 2022-11-18 at 14:47 -0500, Lyude Paul wrote:
> of course, will do in just a moment
> 
> On Fri, 2022-11-18 at 14:46 -0500, Alex Deucher wrote:
> > I've already picked this up.  Can you send a follow up patch with just
> > the coverity fix?
> > 
> > Alex
> > 
> > On Fri, Nov 18, 2022 at 2:17 PM Lyude Paul <lyude@redhat.com> wrote:
> > > 
> > > JFYI, Coverity pointed out one more issue with this series so I'm going to
> > > send out a respin real quick to fix it. It's just a missing variable
> > > assignment (we leave ret unassigned by mistake in
> > > pre_compute_mst_dsc_configs()) so I will carry over your r-b on it.
> > > 
> > > On Wed, 2022-11-16 at 04:39 +0000, Lin, Wayne wrote:
> > > > [Public]
> > > > 
> > > > All the patch set looks good to me. Feel free to add:
> > > > Reviewed-by: Wayne Lin <Wayne.Lin@amd.com>
> > > > 
> > > > Again, thank you Lyude for helping on this!!!
> > > > 
> > > > Regards,
> > > > Wayne
> > > > > -----Original Message-----
> > > > > From: Lyude Paul <lyude@redhat.com>
> > > > > Sent: Tuesday, November 15, 2022 6:18 AM
> > > > > To: amd-gfx@lists.freedesktop.org
> > > > > Cc: Wentland, Harry <Harry.Wentland@amd.com>; stable@vger.kernel.org;
> > > > > Li, Sun peng (Leo) <Sunpeng.Li@amd.com>; Siqueira, Rodrigo
> > > > > <Rodrigo.Siqueira@amd.com>; Deucher, Alexander
> > > > > <Alexander.Deucher@amd.com>; Koenig, Christian
> > > > > <Christian.Koenig@amd.com>; Pan, Xinhui <Xinhui.Pan@amd.com>; David
> > > > > Airlie <airlied@gmail.com>; Daniel Vetter <daniel@ffwll.ch>; Kazlauskas,
> > > > > Nicholas <Nicholas.Kazlauskas@amd.com>; Pillai, Aurabindo
> > > > > <Aurabindo.Pillai@amd.com>; Li, Roman <Roman.Li@amd.com>; Zuo, Jerry
> > > > > <Jerry.Zuo@amd.com>; Wu, Hersen <hersenxs.wu@amd.com>; Lin, Wayne
> > > > > <Wayne.Lin@amd.com>; Thomas Zimmermann <tzimmermann@suse.de>;
> > > > > Mahfooz, Hamza <Hamza.Mahfooz@amd.com>; Hung, Alex
> > > > > <Alex.Hung@amd.com>; Mikita Lipski <mikita.lipski@amd.com>; Liu,
> > > > > Wenjing <Wenjing.Liu@amd.com>; Francis, David
> > > > > <David.Francis@amd.com>; open list:DRM DRIVERS <dri-
> > > > > devel@lists.freedesktop.org>; open list <linux-kernel@vger.kernel.org>
> > > > > Subject: [PATCH v2 1/4] drm/amdgpu/mst: Stop ignoring error codes and
> > > > > deadlocking
> > > > > 
> > > > > It appears that amdgpu makes the mistake of completely ignoring the return
> > > > > values from the DP MST helpers, and instead just returns a simple true/false.
> > > > > In this case, it seems to have come back to bite us because as a result of
> > > > > simply returning false from compute_mst_dsc_configs_for_state(), amdgpu
> > > > > had no way of telling when a deadlock happened from these helpers. This
> > > > > could definitely result in some kernel splats.
> > > > > 
> > > > > V2:
> > > > > * Address Wayne's comments (fix another bunch of spots where we weren't
> > > > >   passing down return codes)
> > > > > 
> > > > > Signed-off-by: Lyude Paul <lyude@redhat.com>
> > > > > Fixes: 8c20a1ed9b4f ("drm/amd/display: MST DSC compute fair share")
> > > > > Cc: Harry Wentland <harry.wentland@amd.com>
> > > > > Cc: <stable@vger.kernel.org> # v5.6+
> > > > > ---
> > > > >  .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |  18 +-
> > > > >  .../display/amdgpu_dm/amdgpu_dm_mst_types.c   | 235 ++++++++++------
> > > > > --
> > > > >  .../display/amdgpu_dm/amdgpu_dm_mst_types.h   |  12 +-
> > > > >  3 files changed, 147 insertions(+), 118 deletions(-)
> > > > > 
> > > > > diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > > > > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > > > > index 0db2a88cd4d7b..852a2100c6b38 100644
> > > > > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > > > > +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > > > > @@ -6462,7 +6462,7 @@ static int
> > > > > dm_update_mst_vcpi_slots_for_dsc(struct drm_atomic_state *state,
> > > > >     struct drm_connector_state *new_con_state;
> > > > >     struct amdgpu_dm_connector *aconnector;
> > > > >     struct dm_connector_state *dm_conn_state;
> > > > > -   int i, j;
> > > > > +   int i, j, ret;
> > > > >     int vcpi, pbn_div, pbn, slot_num = 0;
> > > > > 
> > > > >     for_each_new_connector_in_state(state, connector,
> > > > > new_con_state, i) { @@ -6509,8 +6509,11 @@ static int
> > > > > dm_update_mst_vcpi_slots_for_dsc(struct drm_atomic_state *state,
> > > > >                     dm_conn_state->pbn = pbn;
> > > > >                     dm_conn_state->vcpi_slots = slot_num;
> > > > > 
> > > > > -                   drm_dp_mst_atomic_enable_dsc(state, aconnector-
> > > > > > port, dm_conn_state->pbn,
> > > > > -                                                false);
> > > > > +                   ret = drm_dp_mst_atomic_enable_dsc(state,
> > > > > aconnector->port,
> > > > > +                                                      dm_conn_state-
> > > > > > pbn, false);
> > > > > +                   if (ret < 0)
> > > > > +                           return ret;
> > > > > +
> > > > >                     continue;
> > > > >             }
> > > > > 
> > > > > @@ -9523,10 +9526,9 @@ static int amdgpu_dm_atomic_check(struct
> > > > > drm_device *dev,
> > > > > 
> > > > >  #if defined(CONFIG_DRM_AMD_DC_DCN)
> > > > >     if (dc_resource_is_dsc_encoding_supported(dc)) {
> > > > > -           if (!pre_validate_dsc(state, &dm_state, vars)) {
> > > > > -                   ret = -EINVAL;
> > > > > +           ret = pre_validate_dsc(state, &dm_state, vars);
> > > > > +           if (ret != 0)
> > > > >                     goto fail;
> > > > > -           }
> > > > >     }
> > > > >  #endif
> > > > > 
> > > > > @@ -9621,9 +9623,9 @@ static int amdgpu_dm_atomic_check(struct
> > > > > drm_device *dev,
> > > > >             }
> > > > > 
> > > > >  #if defined(CONFIG_DRM_AMD_DC_DCN)
> > > > > -           if (!compute_mst_dsc_configs_for_state(state, dm_state-
> > > > > > context, vars)) {
> > > > > +           ret = compute_mst_dsc_configs_for_state(state, dm_state-
> > > > > > context, vars);
> > > > > +           if (ret) {
> > > > > 
> > > > >     DRM_DEBUG_DRIVER("compute_mst_dsc_configs_for_state()
> > > > > failed\n");
> > > > > -                   ret = -EINVAL;
> > > > >                     goto fail;
> > > > >             }
> > > > > 
> > > > > diff --git
> > > > > a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > > > > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > > > > index 6ff96b4bdda5c..bba2e8aaa2c20 100644
> > > > > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > > > > +++
> > > > > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > > > > @@ -703,13 +703,13 @@ static int bpp_x16_from_pbn(struct
> > > > > dsc_mst_fairness_params param, int pbn)
> > > > >     return dsc_config.bits_per_pixel;
> > > > >  }
> > > > > 
> > > > > -static bool increase_dsc_bpp(struct drm_atomic_state *state,
> > > > > -                        struct drm_dp_mst_topology_state *mst_state,
> > > > > -                        struct dc_link *dc_link,
> > > > > -                        struct dsc_mst_fairness_params *params,
> > > > > -                        struct dsc_mst_fairness_vars *vars,
> > > > > -                        int count,
> > > > > -                        int k)
> > > > > +static int increase_dsc_bpp(struct drm_atomic_state *state,
> > > > > +                       struct drm_dp_mst_topology_state *mst_state,
> > > > > +                       struct dc_link *dc_link,
> > > > > +                       struct dsc_mst_fairness_params *params,
> > > > > +                       struct dsc_mst_fairness_vars *vars,
> > > > > +                       int count,
> > > > > +                       int k)
> > > > >  {
> > > > >     int i;
> > > > >     bool bpp_increased[MAX_PIPES];
> > > > > @@ -719,6 +719,7 @@ static bool increase_dsc_bpp(struct
> > > > > drm_atomic_state *state,
> > > > >     int remaining_to_increase = 0;
> > > > >     int link_timeslots_used;
> > > > >     int fair_pbn_alloc;
> > > > > +   int ret = 0;
> > > > > 
> > > > >     for (i = 0; i < count; i++) {
> > > > >             if (vars[i + k].dsc_enabled) {
> > > > > @@ -757,52 +758,60 @@ static bool increase_dsc_bpp(struct
> > > > > drm_atomic_state *state,
> > > > > 
> > > > >             if (initial_slack[next_index] > fair_pbn_alloc) {
> > > > >                     vars[next_index].pbn += fair_pbn_alloc;
> > > > > -                   if (drm_dp_atomic_find_time_slots(state,
> > > > > -
> > > > > params[next_index].port->mgr,
> > > > > -
> > > > > params[next_index].port,
> > > > > -
> > > > > vars[next_index].pbn) < 0)
> > > > > -                           return false;
> > > > > -                   if (!drm_dp_mst_atomic_check(state)) {
> > > > > +                   ret = drm_dp_atomic_find_time_slots(state,
> > > > > +
> > > > > params[next_index].port->mgr,
> > > > > +
> > > > > params[next_index].port,
> > > > > +
> > > > > vars[next_index].pbn);
> > > > > +                   if (ret < 0)
> > > > > +                           return ret;
> > > > > +
> > > > > +                   ret = drm_dp_mst_atomic_check(state);
> > > > > +                   if (ret == 0) {
> > > > >                             vars[next_index].bpp_x16 =
> > > > > bpp_x16_from_pbn(params[next_index], vars[next_index].pbn);
> > > > >                     } else {
> > > > >                             vars[next_index].pbn -= fair_pbn_alloc;
> > > > > -                           if (drm_dp_atomic_find_time_slots(state,
> > > > > -
> > > > > params[next_index].port->mgr,
> > > > > -
> > > > > params[next_index].port,
> > > > > -
> > > > > vars[next_index].pbn) < 0)
> > > > > -                                   return false;
> > > > > +                           ret = drm_dp_atomic_find_time_slots(state,
> > > > > +
> > > > > params[next_index].port->mgr,
> > > > > +
> > > > > params[next_index].port,
> > > > > +
> > > > > vars[next_index].pbn);
> > > > > +                           if (ret < 0)
> > > > > +                                   return ret;
> > > > >                     }
> > > > >             } else {
> > > > >                     vars[next_index].pbn += initial_slack[next_index];
> > > > > -                   if (drm_dp_atomic_find_time_slots(state,
> > > > > -
> > > > > params[next_index].port->mgr,
> > > > > -
> > > > > params[next_index].port,
> > > > > -
> > > > > vars[next_index].pbn) < 0)
> > > > > -                           return false;
> > > > > -                   if (!drm_dp_mst_atomic_check(state)) {
> > > > > +                   ret = drm_dp_atomic_find_time_slots(state,
> > > > > +
> > > > > params[next_index].port->mgr,
> > > > > +
> > > > > params[next_index].port,
> > > > > +
> > > > > vars[next_index].pbn);
> > > > > +                   if (ret < 0)
> > > > > +                           return ret;
> > > > > +
> > > > > +                   ret = drm_dp_mst_atomic_check(state);
> > > > > +                   if (ret == 0) {
> > > > >                             vars[next_index].bpp_x16 =
> > > > > params[next_index].bw_range.max_target_bpp_x16;
> > > > >                     } else {
> > > > >                             vars[next_index].pbn -=
> > > > > initial_slack[next_index];
> > > > > -                           if (drm_dp_atomic_find_time_slots(state,
> > > > > -
> > > > > params[next_index].port->mgr,
> > > > > -
> > > > > params[next_index].port,
> > > > > -
> > > > > vars[next_index].pbn) < 0)
> > > > > -                                   return false;
> > > > > +                           ret = drm_dp_atomic_find_time_slots(state,
> > > > > +
> > > > > params[next_index].port->mgr,
> > > > > +
> > > > > params[next_index].port,
> > > > > +
> > > > > vars[next_index].pbn);
> > > > > +                           if (ret < 0)
> > > > > +                                   return ret;
> > > > >                     }
> > > > >             }
> > > > > 
> > > > >             bpp_increased[next_index] = true;
> > > > >             remaining_to_increase--;
> > > > >     }
> > > > > -   return true;
> > > > > +   return 0;
> > > > >  }
> > > > > 
> > > > > -static bool try_disable_dsc(struct drm_atomic_state *state,
> > > > > -                       struct dc_link *dc_link,
> > > > > -                       struct dsc_mst_fairness_params *params,
> > > > > -                       struct dsc_mst_fairness_vars *vars,
> > > > > -                       int count,
> > > > > -                       int k)
> > > > > +static int try_disable_dsc(struct drm_atomic_state *state,
> > > > > +                      struct dc_link *dc_link,
> > > > > +                      struct dsc_mst_fairness_params *params,
> > > > > +                      struct dsc_mst_fairness_vars *vars,
> > > > > +                      int count,
> > > > > +                      int k)
> > > > >  {
> > > > >     int i;
> > > > >     bool tried[MAX_PIPES];
> > > > > @@ -810,6 +819,7 @@ static bool try_disable_dsc(struct drm_atomic_state
> > > > > *state,
> > > > >     int max_kbps_increase;
> > > > >     int next_index;
> > > > >     int remaining_to_try = 0;
> > > > > +   int ret;
> > > > > 
> > > > >     for (i = 0; i < count; i++) {
> > > > >             if (vars[i + k].dsc_enabled
> > > > > @@ -840,49 +850,52 @@ static bool try_disable_dsc(struct
> > > > > drm_atomic_state *state,
> > > > >                     break;
> > > > > 
> > > > >             vars[next_index].pbn =
> > > > > kbps_to_peak_pbn(params[next_index].bw_range.stream_kbps);
> > > > > -           if (drm_dp_atomic_find_time_slots(state,
> > > > > -                                             params[next_index].port-
> > > > > > mgr,
> > > > > -                                             params[next_index].port,
> > > > > -                                             vars[next_index].pbn) < 0)
> > > > > -                   return false;
> > > > > +           ret = drm_dp_atomic_find_time_slots(state,
> > > > > +                                               params[next_index].port-
> > > > > > mgr,
> > > > > +                                               params[next_index].port,
> > > > > +                                               vars[next_index].pbn);
> > > > > +           if (ret < 0)
> > > > > +                   return ret;
> > > > > 
> > > > > -           if (!drm_dp_mst_atomic_check(state)) {
> > > > > +           ret = drm_dp_mst_atomic_check(state);
> > > > > +           if (ret == 0) {
> > > > >                     vars[next_index].dsc_enabled = false;
> > > > >                     vars[next_index].bpp_x16 = 0;
> > > > >             } else {
> > > > >                     vars[next_index].pbn =
> > > > > kbps_to_peak_pbn(params[next_index].bw_range.max_kbps);
> > > > > -                   if (drm_dp_atomic_find_time_slots(state,
> > > > > -
> > > > > params[next_index].port->mgr,
> > > > > -
> > > > > params[next_index].port,
> > > > > -
> > > > > vars[next_index].pbn) < 0)
> > > > > -                           return false;
> > > > > +                   ret = drm_dp_atomic_find_time_slots(state,
> > > > > +
> > > > > params[next_index].port->mgr,
> > > > > +
> > > > > params[next_index].port,
> > > > > +
> > > > > vars[next_index].pbn);
> > > > > +                   if (ret < 0)
> > > > > +                           return ret;
> > > > >             }
> > > > > 
> > > > >             tried[next_index] = true;
> > > > >             remaining_to_try--;
> > > > >     }
> > > > > -   return true;
> > > > > +   return 0;
> > > > >  }
> > > > > 
> > > > > -static bool compute_mst_dsc_configs_for_link(struct drm_atomic_state
> > > > > *state,
> > > > > -                                        struct dc_state *dc_state,
> > > > > -                                        struct dc_link *dc_link,
> > > > > -                                        struct dsc_mst_fairness_vars *vars,
> > > > > -                                        struct drm_dp_mst_topology_mgr
> > > > > *mgr,
> > > > > -                                        int *link_vars_start_index)
> > > > > +static int compute_mst_dsc_configs_for_link(struct drm_atomic_state
> > > > > *state,
> > > > > +                                       struct dc_state *dc_state,
> > > > > +                                       struct dc_link *dc_link,
> > > > > +                                       struct dsc_mst_fairness_vars *vars,
> > > > > +                                       struct drm_dp_mst_topology_mgr
> > > > > *mgr,
> > > > > +                                       int *link_vars_start_index)
> > > > >  {
> > > > >     struct dc_stream_state *stream;
> > > > >     struct dsc_mst_fairness_params params[MAX_PIPES];
> > > > >     struct amdgpu_dm_connector *aconnector;
> > > > >     struct drm_dp_mst_topology_state *mst_state =
> > > > > drm_atomic_get_mst_topology_state(state, mgr);
> > > > >     int count = 0;
> > > > > -   int i, k;
> > > > > +   int i, k, ret;
> > > > >     bool debugfs_overwrite = false;
> > > > > 
> > > > >     memset(params, 0, sizeof(params));
> > > > > 
> > > > >     if (IS_ERR(mst_state))
> > > > > -           return false;
> > > > > +           return PTR_ERR(mst_state);
> > > > > 
> > > > >     mst_state->pbn_div = dm_mst_get_pbn_divider(dc_link);  #if
> > > > > defined(CONFIG_DRM_AMD_DC_DCN) @@ -933,7 +946,7 @@ static bool
> > > > > compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,
> > > > > 
> > > > >     if (count == 0) {
> > > > >             ASSERT(0);
> > > > > -           return true;
> > > > > +           return 0;
> > > > >     }
> > > > > 
> > > > >     /* k is start index of vars for current phy link used by mst hub */ @@
> > > > > -947,13 +960,17 @@ static bool compute_mst_dsc_configs_for_link(struct
> > > > > drm_atomic_state *state,
> > > > >             vars[i + k].pbn =
> > > > > kbps_to_peak_pbn(params[i].bw_range.stream_kbps);
> > > > >             vars[i + k].dsc_enabled = false;
> > > > >             vars[i + k].bpp_x16 = 0;
> > > > > -           if (drm_dp_atomic_find_time_slots(state, params[i].port-
> > > > > > mgr, params[i].port,
> > > > > -                                             vars[i + k].pbn) < 0)
> > > > > -                   return false;
> > > > > +           ret = drm_dp_atomic_find_time_slots(state, params[i].port-
> > > > > > mgr, params[i].port,
> > > > > +                                               vars[i + k].pbn);
> > > > > +           if (ret < 0)
> > > > > +                   return ret;
> > > > >     }
> > > > > -   if (!drm_dp_mst_atomic_check(state) && !debugfs_overwrite) {
> > > > > +   ret = drm_dp_mst_atomic_check(state);
> > > > > +   if (ret == 0 && !debugfs_overwrite) {
> > > > >             set_dsc_configs_from_fairness_vars(params, vars, count, k);
> > > > > -           return true;
> > > > > +           return 0;
> > > > > +   } else if (ret != -ENOSPC) {
> > > > > +           return ret;
> > > > >     }
> > > > > 
> > > > >     /* Try max compression */
> > > > > @@ -962,31 +979,36 @@ static bool
> > > > > compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,
> > > > >                     vars[i + k].pbn =
> > > > > kbps_to_peak_pbn(params[i].bw_range.min_kbps);
> > > > >                     vars[i + k].dsc_enabled = true;
> > > > >                     vars[i + k].bpp_x16 =
> > > > > params[i].bw_range.min_target_bpp_x16;
> > > > > -                   if (drm_dp_atomic_find_time_slots(state,
> > > > > params[i].port->mgr,
> > > > > -                                                     params[i].port, vars[i
> > > > > + k].pbn) < 0)
> > > > > -                           return false;
> > > > > +                   ret = drm_dp_atomic_find_time_slots(state,
> > > > > params[i].port->mgr,
> > > > > +                                                       params[i].port,
> > > > > vars[i + k].pbn);
> > > > > +                   if (ret < 0)
> > > > > +                           return ret;
> > > > >             } else {
> > > > >                     vars[i + k].pbn =
> > > > > kbps_to_peak_pbn(params[i].bw_range.stream_kbps);
> > > > >                     vars[i + k].dsc_enabled = false;
> > > > >                     vars[i + k].bpp_x16 = 0;
> > > > > -                   if (drm_dp_atomic_find_time_slots(state,
> > > > > params[i].port->mgr,
> > > > > -                                                     params[i].port, vars[i
> > > > > + k].pbn) < 0)
> > > > > -                           return false;
> > > > > +                   ret = drm_dp_atomic_find_time_slots(state,
> > > > > params[i].port->mgr,
> > > > > +                                                       params[i].port,
> > > > > vars[i + k].pbn);
> > > > > +                   if (ret < 0)
> > > > > +                           return ret;
> > > > >             }
> > > > >     }
> > > > > -   if (drm_dp_mst_atomic_check(state))
> > > > > -           return false;
> > > > > +   ret = drm_dp_mst_atomic_check(state);
> > > > > +   if (ret != 0)
> > > > > +           return ret;
> > > > > 
> > > > >     /* Optimize degree of compression */
> > > > > -   if (!increase_dsc_bpp(state, mst_state, dc_link, params, vars, count,
> > > > > k))
> > > > > -           return false;
> > > > > +   ret = increase_dsc_bpp(state, mst_state, dc_link, params, vars,
> > > > > count, k);
> > > > > +   if (ret < 0)
> > > > > +           return ret;
> > > > > 
> > > > > -   if (!try_disable_dsc(state, dc_link, params, vars, count, k))
> > > > > -           return false;
> > > > > +   ret = try_disable_dsc(state, dc_link, params, vars, count, k);
> > > > > +   if (ret < 0)
> > > > > +           return ret;
> > > > > 
> > > > >     set_dsc_configs_from_fairness_vars(params, vars, count, k);
> > > > > 
> > > > > -   return true;
> > > > > +   return 0;
> > > > >  }
> > > > > 
> > > > >  static bool is_dsc_need_re_compute(
> > > > > @@ -1087,15 +1109,16 @@ static bool is_dsc_need_re_compute(
> > > > >     return is_dsc_need_re_compute;
> > > > >  }
> > > > > 
> > > > > -bool compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> > > > > -                                  struct dc_state *dc_state,
> > > > > -                                  struct dsc_mst_fairness_vars *vars)
> > > > > +int compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> > > > > +                                 struct dc_state *dc_state,
> > > > > +                                 struct dsc_mst_fairness_vars *vars)
> > > > >  {
> > > > >     int i, j;
> > > > >     struct dc_stream_state *stream;
> > > > >     bool computed_streams[MAX_PIPES];
> > > > >     struct amdgpu_dm_connector *aconnector;
> > > > >     int link_vars_start_index = 0;
> > > > > +   int ret = 0;
> > > > > 
> > > > >     for (i = 0; i < dc_state->stream_count; i++)
> > > > >             computed_streams[i] = false;
> > > > > @@ -1118,17 +1141,19 @@ bool compute_mst_dsc_configs_for_state(struct
> > > > > drm_atomic_state *state,
> > > > >                     continue;
> > > > > 
> > > > >             if (dcn20_remove_stream_from_ctx(stream->ctx->dc,
> > > > > dc_state, stream) != DC_OK)
> > > > > -                   return false;
> > > > > +                   return -EINVAL;
> > > > > 
> > > > >             if (!is_dsc_need_re_compute(state, dc_state, stream->link))
> > > > >                     continue;
> > > > > 
> > > > >             mutex_lock(&aconnector->mst_mgr.lock);
> > > > > -           if (!compute_mst_dsc_configs_for_link(state, dc_state,
> > > > > stream->link, vars,
> > > > > -                                                 &aconnector->mst_mgr,
> > > > > -                                                 &link_vars_start_index)) {
> > > > > +
> > > > > +           ret = compute_mst_dsc_configs_for_link(state, dc_state,
> > > > > stream->link, vars,
> > > > > +                                                  &aconnector->mst_mgr,
> > > > > +                                                  &link_vars_start_index);
> > > > > +           if (ret != 0) {
> > > > >                     mutex_unlock(&aconnector->mst_mgr.lock);
> > > > > -                   return false;
> > > > > +                   return ret;
> > > > >             }
> > > > >             mutex_unlock(&aconnector->mst_mgr.lock);
> > > > > 
> > > > > @@ -1143,22 +1168,22 @@ bool compute_mst_dsc_configs_for_state(struct
> > > > > drm_atomic_state *state,
> > > > > 
> > > > >             if (stream->timing.flags.DSC == 1)
> > > > >                     if (dc_stream_add_dsc_to_resource(stream->ctx-
> > > > > > dc, dc_state, stream) != DC_OK)
> > > > > -                           return false;
> > > > > +                           return -EINVAL;
> > > > >     }
> > > > > 
> > > > > -   return true;
> > > > > +   return ret;
> > > > >  }
> > > > > 
> > > > > -static bool
> > > > > -   pre_compute_mst_dsc_configs_for_state(struct drm_atomic_state
> > > > > *state,
> > > > > -                                         struct dc_state *dc_state,
> > > > > -                                         struct dsc_mst_fairness_vars
> > > > > *vars)
> > > > > +static int pre_compute_mst_dsc_configs_for_state(struct
> > > > > drm_atomic_state *state,
> > > > > +                                            struct dc_state *dc_state,
> > > > > +                                            struct dsc_mst_fairness_vars
> > > > > *vars)
> > > > >  {
> > > > >     int i, j;
> > > > >     struct dc_stream_state *stream;
> > > > >     bool computed_streams[MAX_PIPES];
> > > > >     struct amdgpu_dm_connector *aconnector;
> > > > >     int link_vars_start_index = 0;
> > > > > +   int ret;
> > > > > 
> > > > >     for (i = 0; i < dc_state->stream_count; i++)
> > > > >             computed_streams[i] = false;
> > > > > @@ -1184,11 +1209,12 @@ static bool
> > > > >                     continue;
> > > > > 
> > > > >             mutex_lock(&aconnector->mst_mgr.lock);
> > > > > -           if (!compute_mst_dsc_configs_for_link(state, dc_state,
> > > > > stream->link, vars,
> > > > > -                                                 &aconnector->mst_mgr,
> > > > > -                                                 &link_vars_start_index)) {
> > > > > +           ret = compute_mst_dsc_configs_for_link(state, dc_state,
> > > > > stream->link, vars,
> > > > > +                                                  &aconnector->mst_mgr,
> > > > > +                                                  &link_vars_start_index);
> > > > > +           if (ret != 0) {
> > > > >                     mutex_unlock(&aconnector->mst_mgr.lock);
> > > > > -                   return false;
> > > > > +                   return ret;
> > > > >             }
> > > > >             mutex_unlock(&aconnector->mst_mgr.lock);
> > > > > 
> > > > > @@ -1198,7 +1224,7 @@ static bool
> > > > >             }
> > > > >     }
> > > > > 
> > > > > -   return true;
> > > > > +   return ret;
> > > > >  }
> > > > > 
> > > > >  static int find_crtc_index_in_state_by_stream(struct drm_atomic_state
> > > > > *state, @@ -1253,9 +1279,9 @@ static bool
> > > > > is_dsc_precompute_needed(struct drm_atomic_state *state)
> > > > >     return ret;
> > > > >  }
> > > > > 
> > > > > -bool pre_validate_dsc(struct drm_atomic_state *state,
> > > > > -                 struct dm_atomic_state **dm_state_ptr,
> > > > > -                 struct dsc_mst_fairness_vars *vars)
> > > > > +int pre_validate_dsc(struct drm_atomic_state *state,
> > > > > +                struct dm_atomic_state **dm_state_ptr,
> > > > > +                struct dsc_mst_fairness_vars *vars)
> > > > >  {
> > > > >     int i;
> > > > >     struct dm_atomic_state *dm_state;
> > > > > @@ -1264,11 +1290,12 @@ bool pre_validate_dsc(struct drm_atomic_state
> > > > > *state,
> > > > > 
> > > > >     if (!is_dsc_precompute_needed(state)) {
> > > > >             DRM_INFO_ONCE("DSC precompute is not needed.\n");
> > > > > -           return true;
> > > > > +           return 0;
> > > > >     }
> > > > > -   if (dm_atomic_get_state(state, dm_state_ptr)) {
> > > > > +   ret = dm_atomic_get_state(state, dm_state_ptr);
> > > > > +   if (ret != 0) {
> > > > >             DRM_INFO_ONCE("dm_atomic_get_state() failed\n");
> > > > > -           return false;
> > > > > +           return ret;
> > > > >     }
> > > > >     dm_state = *dm_state_ptr;
> > > > > 
> > > > > @@ -1280,7 +1307,7 @@ bool pre_validate_dsc(struct drm_atomic_state
> > > > > *state,
> > > > > 
> > > > >     local_dc_state = kmemdup(dm_state->context, sizeof(struct
> > > > > dc_state), GFP_KERNEL);
> > > > >     if (!local_dc_state)
> > > > > -           return false;
> > > > > +           return -ENOMEM;
> > > > > 
> > > > >     for (i = 0; i < local_dc_state->stream_count; i++) {
> > > > >             struct dc_stream_state *stream = dm_state->context-
> > > > > > streams[i]; @@ -1316,9 +1343,9 @@ bool pre_validate_dsc(struct
> > > > > drm_atomic_state *state,
> > > > >     if (ret != 0)
> > > > >             goto clean_exit;
> > > > > 
> > > > > -   if (!pre_compute_mst_dsc_configs_for_state(state, local_dc_state,
> > > > > vars)) {
> > > > > +   ret = pre_compute_mst_dsc_configs_for_state(state, local_dc_state,
> > > > > vars);
> > > > > +   if (ret != 0) {
> > > > > 
> > > > >     DRM_INFO_ONCE("pre_compute_mst_dsc_configs_for_state()
> > > > > failed\n");
> > > > > -           ret = -EINVAL;
> > > > >             goto clean_exit;
> > > > >     }
> > > > > 
> > > > > @@ -1349,7 +1376,7 @@ bool pre_validate_dsc(struct drm_atomic_state
> > > > > *state,
> > > > > 
> > > > >     kfree(local_dc_state);
> > > > > 
> > > > > -   return (ret == 0);
> > > > > +   return ret;
> > > > >  }
> > > > > 
> > > > >  static unsigned int kbps_from_pbn(unsigned int pbn) diff --git
> > > > > a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> > > > > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> > > > > index b92a7c5671aa2..97fd70df531bf 100644
> > > > > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> > > > > +++
> > > > > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> > > > > @@ -53,15 +53,15 @@ struct dsc_mst_fairness_vars {
> > > > >     struct amdgpu_dm_connector *aconnector;  };
> > > > > 
> > > > > -bool compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> > > > > -                                  struct dc_state *dc_state,
> > > > > -                                  struct dsc_mst_fairness_vars *vars);
> > > > > +int compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> > > > > +                                 struct dc_state *dc_state,
> > > > > +                                 struct dsc_mst_fairness_vars *vars);
> > > > > 
> > > > >  bool needs_dsc_aux_workaround(struct dc_link *link);
> > > > > 
> > > > > -bool pre_validate_dsc(struct drm_atomic_state *state,
> > > > > -                 struct dm_atomic_state **dm_state_ptr,
> > > > > -                 struct dsc_mst_fairness_vars *vars);
> > > > > +int pre_validate_dsc(struct drm_atomic_state *state,
> > > > > +                struct dm_atomic_state **dm_state_ptr,
> > > > > +                struct dsc_mst_fairness_vars *vars);
> > > > > 
> > > > >  enum dc_status dm_dp_mst_is_port_support_mode(
> > > > >     struct amdgpu_dm_connector *aconnector,
> > > > > --
> > > > > 2.37.3
> > > > 
> > > 
> > > --
> > > Cheers,
> > >  Lyude Paul (she/her)
> > >  Software Engineer at Red Hat
> > > 
> > 
>
  

On Fri, Nov 18, 2022 at 2:53 PM Lyude Paul <lyude@redhat.com> wrote:
>
> JFYI - I'm not sure of the correct commit ID to add for the Fixes: tag since
> it's in your branch, so I'll omit that and let you add it into the patch

Yeah, I'll add that.  Many thanks!

Alex

>
> On Fri, 2022-11-18 at 14:47 -0500, Lyude Paul wrote:
> > of course, will do in just a moment
> >
> > On Fri, 2022-11-18 at 14:46 -0500, Alex Deucher wrote:
> > > I've already picked this up.  Can you send a follow up patch with just
> > > the coverity fix?
> > >
> > > Alex
> > >
> > > On Fri, Nov 18, 2022 at 2:17 PM Lyude Paul <lyude@redhat.com> wrote:
> > > >
> > > > JFYI, Coverity pointed out one more issue with this series so I'm going to
> > > > send out a respin real quick to fix it. It's just a missing variable
> > > > assignment (we leave ret unassigned by mistake in
> > > > pre_compute_mst_dsc_configs()) so I will carry over your r-b on it.
> > > >
> > > > On Wed, 2022-11-16 at 04:39 +0000, Lin, Wayne wrote:
> > > > > [Public]
> > > > >
> > > > > All the patch set looks good to me. Feel free to add:
> > > > > Reviewed-by: Wayne Lin <Wayne.Lin@amd.com>
> > > > >
> > > > > Again, thank you Lyude for helping on this!!!
> > > > >
> > > > > Regards,
> > > > > Wayne
> > > > > > -----Original Message-----
> > > > > > From: Lyude Paul <lyude@redhat.com>
> > > > > > Sent: Tuesday, November 15, 2022 6:18 AM
> > > > > > To: amd-gfx@lists.freedesktop.org
> > > > > > Cc: Wentland, Harry <Harry.Wentland@amd.com>; stable@vger.kernel.org;
> > > > > > Li, Sun peng (Leo) <Sunpeng.Li@amd.com>; Siqueira, Rodrigo
> > > > > > <Rodrigo.Siqueira@amd.com>; Deucher, Alexander
> > > > > > <Alexander.Deucher@amd.com>; Koenig, Christian
> > > > > > <Christian.Koenig@amd.com>; Pan, Xinhui <Xinhui.Pan@amd.com>; David
> > > > > > Airlie <airlied@gmail.com>; Daniel Vetter <daniel@ffwll.ch>; Kazlauskas,
> > > > > > Nicholas <Nicholas.Kazlauskas@amd.com>; Pillai, Aurabindo
> > > > > > <Aurabindo.Pillai@amd.com>; Li, Roman <Roman.Li@amd.com>; Zuo, Jerry
> > > > > > <Jerry.Zuo@amd.com>; Wu, Hersen <hersenxs.wu@amd.com>; Lin, Wayne
> > > > > > <Wayne.Lin@amd.com>; Thomas Zimmermann <tzimmermann@suse.de>;
> > > > > > Mahfooz, Hamza <Hamza.Mahfooz@amd.com>; Hung, Alex
> > > > > > <Alex.Hung@amd.com>; Mikita Lipski <mikita.lipski@amd.com>; Liu,
> > > > > > Wenjing <Wenjing.Liu@amd.com>; Francis, David
> > > > > > <David.Francis@amd.com>; open list:DRM DRIVERS <dri-
> > > > > > devel@lists.freedesktop.org>; open list <linux-kernel@vger.kernel.org>
> > > > > > Subject: [PATCH v2 1/4] drm/amdgpu/mst: Stop ignoring error codes and
> > > > > > deadlocking
> > > > > >
> > > > > > It appears that amdgpu makes the mistake of completely ignoring the return
> > > > > > values from the DP MST helpers, and instead just returns a simple true/false.
> > > > > > In this case, it seems to have come back to bite us because as a result of
> > > > > > simply returning false from compute_mst_dsc_configs_for_state(), amdgpu
> > > > > > had no way of telling when a deadlock happened from these helpers. This
> > > > > > could definitely result in some kernel splats.
> > > > > >
> > > > > > V2:
> > > > > > * Address Wayne's comments (fix another bunch of spots where we weren't
> > > > > >   passing down return codes)
> > > > > >
> > > > > > Signed-off-by: Lyude Paul <lyude@redhat.com>
> > > > > > Fixes: 8c20a1ed9b4f ("drm/amd/display: MST DSC compute fair share")
> > > > > > Cc: Harry Wentland <harry.wentland@amd.com>
> > > > > > Cc: <stable@vger.kernel.org> # v5.6+
> > > > > > ---
> > > > > >  .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c |  18 +-
> > > > > >  .../display/amdgpu_dm/amdgpu_dm_mst_types.c   | 235 ++++++++++------
> > > > > > --
> > > > > >  .../display/amdgpu_dm/amdgpu_dm_mst_types.h   |  12 +-
> > > > > >  3 files changed, 147 insertions(+), 118 deletions(-)
> > > > > >
> > > > > > diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > > > > > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > > > > > index 0db2a88cd4d7b..852a2100c6b38 100644
> > > > > > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > > > > > +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > > > > > @@ -6462,7 +6462,7 @@ static int
> > > > > > dm_update_mst_vcpi_slots_for_dsc(struct drm_atomic_state *state,
> > > > > >     struct drm_connector_state *new_con_state;
> > > > > >     struct amdgpu_dm_connector *aconnector;
> > > > > >     struct dm_connector_state *dm_conn_state;
> > > > > > -   int i, j;
> > > > > > +   int i, j, ret;
> > > > > >     int vcpi, pbn_div, pbn, slot_num = 0;
> > > > > >
> > > > > >     for_each_new_connector_in_state(state, connector,
> > > > > > new_con_state, i) { @@ -6509,8 +6509,11 @@ static int
> > > > > > dm_update_mst_vcpi_slots_for_dsc(struct drm_atomic_state *state,
> > > > > >                     dm_conn_state->pbn = pbn;
> > > > > >                     dm_conn_state->vcpi_slots = slot_num;
> > > > > >
> > > > > > -                   drm_dp_mst_atomic_enable_dsc(state, aconnector-
> > > > > > > port, dm_conn_state->pbn,
> > > > > > -                                                false);
> > > > > > +                   ret = drm_dp_mst_atomic_enable_dsc(state,
> > > > > > aconnector->port,
> > > > > > +                                                      dm_conn_state-
> > > > > > > pbn, false);
> > > > > > +                   if (ret < 0)
> > > > > > +                           return ret;
> > > > > > +
> > > > > >                     continue;
> > > > > >             }
> > > > > >
> > > > > > @@ -9523,10 +9526,9 @@ static int amdgpu_dm_atomic_check(struct
> > > > > > drm_device *dev,
> > > > > >
> > > > > >  #if defined(CONFIG_DRM_AMD_DC_DCN)
> > > > > >     if (dc_resource_is_dsc_encoding_supported(dc)) {
> > > > > > -           if (!pre_validate_dsc(state, &dm_state, vars)) {
> > > > > > -                   ret = -EINVAL;
> > > > > > +           ret = pre_validate_dsc(state, &dm_state, vars);
> > > > > > +           if (ret != 0)
> > > > > >                     goto fail;
> > > > > > -           }
> > > > > >     }
> > > > > >  #endif
> > > > > >
> > > > > > @@ -9621,9 +9623,9 @@ static int amdgpu_dm_atomic_check(struct
> > > > > > drm_device *dev,
> > > > > >             }
> > > > > >
> > > > > >  #if defined(CONFIG_DRM_AMD_DC_DCN)
> > > > > > -           if (!compute_mst_dsc_configs_for_state(state, dm_state-
> > > > > > > context, vars)) {
> > > > > > +           ret = compute_mst_dsc_configs_for_state(state, dm_state-
> > > > > > > context, vars);
> > > > > > +           if (ret) {
> > > > > >
> > > > > >     DRM_DEBUG_DRIVER("compute_mst_dsc_configs_for_state()
> > > > > > failed\n");
> > > > > > -                   ret = -EINVAL;
> > > > > >                     goto fail;
> > > > > >             }
> > > > > >
> > > > > > diff --git
> > > > > > a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > > > > > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > > > > > index 6ff96b4bdda5c..bba2e8aaa2c20 100644
> > > > > > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > > > > > +++
> > > > > > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > > > > > @@ -703,13 +703,13 @@ static int bpp_x16_from_pbn(struct
> > > > > > dsc_mst_fairness_params param, int pbn)
> > > > > >     return dsc_config.bits_per_pixel;
> > > > > >  }
> > > > > >
> > > > > > -static bool increase_dsc_bpp(struct drm_atomic_state *state,
> > > > > > -                        struct drm_dp_mst_topology_state *mst_state,
> > > > > > -                        struct dc_link *dc_link,
> > > > > > -                        struct dsc_mst_fairness_params *params,
> > > > > > -                        struct dsc_mst_fairness_vars *vars,
> > > > > > -                        int count,
> > > > > > -                        int k)
> > > > > > +static int increase_dsc_bpp(struct drm_atomic_state *state,
> > > > > > +                       struct drm_dp_mst_topology_state *mst_state,
> > > > > > +                       struct dc_link *dc_link,
> > > > > > +                       struct dsc_mst_fairness_params *params,
> > > > > > +                       struct dsc_mst_fairness_vars *vars,
> > > > > > +                       int count,
> > > > > > +                       int k)
> > > > > >  {
> > > > > >     int i;
> > > > > >     bool bpp_increased[MAX_PIPES];
> > > > > > @@ -719,6 +719,7 @@ static bool increase_dsc_bpp(struct
> > > > > > drm_atomic_state *state,
> > > > > >     int remaining_to_increase = 0;
> > > > > >     int link_timeslots_used;
> > > > > >     int fair_pbn_alloc;
> > > > > > +   int ret = 0;
> > > > > >
> > > > > >     for (i = 0; i < count; i++) {
> > > > > >             if (vars[i + k].dsc_enabled) {
> > > > > > @@ -757,52 +758,60 @@ static bool increase_dsc_bpp(struct
> > > > > > drm_atomic_state *state,
> > > > > >
> > > > > >             if (initial_slack[next_index] > fair_pbn_alloc) {
> > > > > >                     vars[next_index].pbn += fair_pbn_alloc;
> > > > > > -                   if (drm_dp_atomic_find_time_slots(state,
> > > > > > -
> > > > > > params[next_index].port->mgr,
> > > > > > -
> > > > > > params[next_index].port,
> > > > > > -
> > > > > > vars[next_index].pbn) < 0)
> > > > > > -                           return false;
> > > > > > -                   if (!drm_dp_mst_atomic_check(state)) {
> > > > > > +                   ret = drm_dp_atomic_find_time_slots(state,
> > > > > > +
> > > > > > params[next_index].port->mgr,
> > > > > > +
> > > > > > params[next_index].port,
> > > > > > +
> > > > > > vars[next_index].pbn);
> > > > > > +                   if (ret < 0)
> > > > > > +                           return ret;
> > > > > > +
> > > > > > +                   ret = drm_dp_mst_atomic_check(state);
> > > > > > +                   if (ret == 0) {
> > > > > >                             vars[next_index].bpp_x16 =
> > > > > > bpp_x16_from_pbn(params[next_index], vars[next_index].pbn);
> > > > > >                     } else {
> > > > > >                             vars[next_index].pbn -= fair_pbn_alloc;
> > > > > > -                           if (drm_dp_atomic_find_time_slots(state,
> > > > > > -
> > > > > > params[next_index].port->mgr,
> > > > > > -
> > > > > > params[next_index].port,
> > > > > > -
> > > > > > vars[next_index].pbn) < 0)
> > > > > > -                                   return false;
> > > > > > +                           ret = drm_dp_atomic_find_time_slots(state,
> > > > > > +
> > > > > > params[next_index].port->mgr,
> > > > > > +
> > > > > > params[next_index].port,
> > > > > > +
> > > > > > vars[next_index].pbn);
> > > > > > +                           if (ret < 0)
> > > > > > +                                   return ret;
> > > > > >                     }
> > > > > >             } else {
> > > > > >                     vars[next_index].pbn += initial_slack[next_index];
> > > > > > -                   if (drm_dp_atomic_find_time_slots(state,
> > > > > > -
> > > > > > params[next_index].port->mgr,
> > > > > > -
> > > > > > params[next_index].port,
> > > > > > -
> > > > > > vars[next_index].pbn) < 0)
> > > > > > -                           return false;
> > > > > > -                   if (!drm_dp_mst_atomic_check(state)) {
> > > > > > +                   ret = drm_dp_atomic_find_time_slots(state,
> > > > > > +
> > > > > > params[next_index].port->mgr,
> > > > > > +
> > > > > > params[next_index].port,
> > > > > > +
> > > > > > vars[next_index].pbn);
> > > > > > +                   if (ret < 0)
> > > > > > +                           return ret;
> > > > > > +
> > > > > > +                   ret = drm_dp_mst_atomic_check(state);
> > > > > > +                   if (ret == 0) {
> > > > > >                             vars[next_index].bpp_x16 =
> > > > > > params[next_index].bw_range.max_target_bpp_x16;
> > > > > >                     } else {
> > > > > >                             vars[next_index].pbn -=
> > > > > > initial_slack[next_index];
> > > > > > -                           if (drm_dp_atomic_find_time_slots(state,
> > > > > > -
> > > > > > params[next_index].port->mgr,
> > > > > > -
> > > > > > params[next_index].port,
> > > > > > -
> > > > > > vars[next_index].pbn) < 0)
> > > > > > -                                   return false;
> > > > > > +                           ret = drm_dp_atomic_find_time_slots(state,
> > > > > > +
> > > > > > params[next_index].port->mgr,
> > > > > > +
> > > > > > params[next_index].port,
> > > > > > +
> > > > > > vars[next_index].pbn);
> > > > > > +                           if (ret < 0)
> > > > > > +                                   return ret;
> > > > > >                     }
> > > > > >             }
> > > > > >
> > > > > >             bpp_increased[next_index] = true;
> > > > > >             remaining_to_increase--;
> > > > > >     }
> > > > > > -   return true;
> > > > > > +   return 0;
> > > > > >  }
> > > > > >
> > > > > > -static bool try_disable_dsc(struct drm_atomic_state *state,
> > > > > > -                       struct dc_link *dc_link,
> > > > > > -                       struct dsc_mst_fairness_params *params,
> > > > > > -                       struct dsc_mst_fairness_vars *vars,
> > > > > > -                       int count,
> > > > > > -                       int k)
> > > > > > +static int try_disable_dsc(struct drm_atomic_state *state,
> > > > > > +                      struct dc_link *dc_link,
> > > > > > +                      struct dsc_mst_fairness_params *params,
> > > > > > +                      struct dsc_mst_fairness_vars *vars,
> > > > > > +                      int count,
> > > > > > +                      int k)
> > > > > >  {
> > > > > >     int i;
> > > > > >     bool tried[MAX_PIPES];
> > > > > > @@ -810,6 +819,7 @@ static bool try_disable_dsc(struct drm_atomic_state
> > > > > > *state,
> > > > > >     int max_kbps_increase;
> > > > > >     int next_index;
> > > > > >     int remaining_to_try = 0;
> > > > > > +   int ret;
> > > > > >
> > > > > >     for (i = 0; i < count; i++) {
> > > > > >             if (vars[i + k].dsc_enabled
> > > > > > @@ -840,49 +850,52 @@ static bool try_disable_dsc(struct
> > > > > > drm_atomic_state *state,
> > > > > >                     break;
> > > > > >
> > > > > >             vars[next_index].pbn =
> > > > > > kbps_to_peak_pbn(params[next_index].bw_range.stream_kbps);
> > > > > > -           if (drm_dp_atomic_find_time_slots(state,
> > > > > > -                                             params[next_index].port-
> > > > > > > mgr,
> > > > > > -                                             params[next_index].port,
> > > > > > -                                             vars[next_index].pbn) < 0)
> > > > > > -                   return false;
> > > > > > +           ret = drm_dp_atomic_find_time_slots(state,
> > > > > > +                                               params[next_index].port-
> > > > > > > mgr,
> > > > > > +                                               params[next_index].port,
> > > > > > +                                               vars[next_index].pbn);
> > > > > > +           if (ret < 0)
> > > > > > +                   return ret;
> > > > > >
> > > > > > -           if (!drm_dp_mst_atomic_check(state)) {
> > > > > > +           ret = drm_dp_mst_atomic_check(state);
> > > > > > +           if (ret == 0) {
> > > > > >                     vars[next_index].dsc_enabled = false;
> > > > > >                     vars[next_index].bpp_x16 = 0;
> > > > > >             } else {
> > > > > >                     vars[next_index].pbn =
> > > > > > kbps_to_peak_pbn(params[next_index].bw_range.max_kbps);
> > > > > > -                   if (drm_dp_atomic_find_time_slots(state,
> > > > > > -
> > > > > > params[next_index].port->mgr,
> > > > > > -
> > > > > > params[next_index].port,
> > > > > > -
> > > > > > vars[next_index].pbn) < 0)
> > > > > > -                           return false;
> > > > > > +                   ret = drm_dp_atomic_find_time_slots(state,
> > > > > > +
> > > > > > params[next_index].port->mgr,
> > > > > > +
> > > > > > params[next_index].port,
> > > > > > +
> > > > > > vars[next_index].pbn);
> > > > > > +                   if (ret < 0)
> > > > > > +                           return ret;
> > > > > >             }
> > > > > >
> > > > > >             tried[next_index] = true;
> > > > > >             remaining_to_try--;
> > > > > >     }
> > > > > > -   return true;
> > > > > > +   return 0;
> > > > > >  }
> > > > > >
> > > > > > -static bool compute_mst_dsc_configs_for_link(struct drm_atomic_state
> > > > > > *state,
> > > > > > -                                        struct dc_state *dc_state,
> > > > > > -                                        struct dc_link *dc_link,
> > > > > > -                                        struct dsc_mst_fairness_vars *vars,
> > > > > > -                                        struct drm_dp_mst_topology_mgr
> > > > > > *mgr,
> > > > > > -                                        int *link_vars_start_index)
> > > > > > +static int compute_mst_dsc_configs_for_link(struct drm_atomic_state
> > > > > > *state,
> > > > > > +                                       struct dc_state *dc_state,
> > > > > > +                                       struct dc_link *dc_link,
> > > > > > +                                       struct dsc_mst_fairness_vars *vars,
> > > > > > +                                       struct drm_dp_mst_topology_mgr
> > > > > > *mgr,
> > > > > > +                                       int *link_vars_start_index)
> > > > > >  {
> > > > > >     struct dc_stream_state *stream;
> > > > > >     struct dsc_mst_fairness_params params[MAX_PIPES];
> > > > > >     struct amdgpu_dm_connector *aconnector;
> > > > > >     struct drm_dp_mst_topology_state *mst_state =
> > > > > > drm_atomic_get_mst_topology_state(state, mgr);
> > > > > >     int count = 0;
> > > > > > -   int i, k;
> > > > > > +   int i, k, ret;
> > > > > >     bool debugfs_overwrite = false;
> > > > > >
> > > > > >     memset(params, 0, sizeof(params));
> > > > > >
> > > > > >     if (IS_ERR(mst_state))
> > > > > > -           return false;
> > > > > > +           return PTR_ERR(mst_state);
> > > > > >
> > > > > >     mst_state->pbn_div = dm_mst_get_pbn_divider(dc_link);  #if
> > > > > > defined(CONFIG_DRM_AMD_DC_DCN) @@ -933,7 +946,7 @@ static bool
> > > > > > compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,
> > > > > >
> > > > > >     if (count == 0) {
> > > > > >             ASSERT(0);
> > > > > > -           return true;
> > > > > > +           return 0;
> > > > > >     }
> > > > > >
> > > > > >     /* k is start index of vars for current phy link used by mst hub */ @@
> > > > > > -947,13 +960,17 @@ static bool compute_mst_dsc_configs_for_link(struct
> > > > > > drm_atomic_state *state,
> > > > > >             vars[i + k].pbn =
> > > > > > kbps_to_peak_pbn(params[i].bw_range.stream_kbps);
> > > > > >             vars[i + k].dsc_enabled = false;
> > > > > >             vars[i + k].bpp_x16 = 0;
> > > > > > -           if (drm_dp_atomic_find_time_slots(state, params[i].port-
> > > > > > > mgr, params[i].port,
> > > > > > -                                             vars[i + k].pbn) < 0)
> > > > > > -                   return false;
> > > > > > +           ret = drm_dp_atomic_find_time_slots(state, params[i].port-
> > > > > > > mgr, params[i].port,
> > > > > > +                                               vars[i + k].pbn);
> > > > > > +           if (ret < 0)
> > > > > > +                   return ret;
> > > > > >     }
> > > > > > -   if (!drm_dp_mst_atomic_check(state) && !debugfs_overwrite) {
> > > > > > +   ret = drm_dp_mst_atomic_check(state);
> > > > > > +   if (ret == 0 && !debugfs_overwrite) {
> > > > > >             set_dsc_configs_from_fairness_vars(params, vars, count, k);
> > > > > > -           return true;
> > > > > > +           return 0;
> > > > > > +   } else if (ret != -ENOSPC) {
> > > > > > +           return ret;
> > > > > >     }
> > > > > >
> > > > > >     /* Try max compression */
> > > > > > @@ -962,31 +979,36 @@ static bool
> > > > > > compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,
> > > > > >                     vars[i + k].pbn =
> > > > > > kbps_to_peak_pbn(params[i].bw_range.min_kbps);
> > > > > >                     vars[i + k].dsc_enabled = true;
> > > > > >                     vars[i + k].bpp_x16 =
> > > > > > params[i].bw_range.min_target_bpp_x16;
> > > > > > -                   if (drm_dp_atomic_find_time_slots(state,
> > > > > > params[i].port->mgr,
> > > > > > -                                                     params[i].port, vars[i
> > > > > > + k].pbn) < 0)
> > > > > > -                           return false;
> > > > > > +                   ret = drm_dp_atomic_find_time_slots(state,
> > > > > > params[i].port->mgr,
> > > > > > +                                                       params[i].port,
> > > > > > vars[i + k].pbn);
> > > > > > +                   if (ret < 0)
> > > > > > +                           return ret;
> > > > > >             } else {
> > > > > >                     vars[i + k].pbn =
> > > > > > kbps_to_peak_pbn(params[i].bw_range.stream_kbps);
> > > > > >                     vars[i + k].dsc_enabled = false;
> > > > > >                     vars[i + k].bpp_x16 = 0;
> > > > > > -                   if (drm_dp_atomic_find_time_slots(state,
> > > > > > params[i].port->mgr,
> > > > > > -                                                     params[i].port, vars[i
> > > > > > + k].pbn) < 0)
> > > > > > -                           return false;
> > > > > > +                   ret = drm_dp_atomic_find_time_slots(state,
> > > > > > params[i].port->mgr,
> > > > > > +                                                       params[i].port,
> > > > > > vars[i + k].pbn);
> > > > > > +                   if (ret < 0)
> > > > > > +                           return ret;
> > > > > >             }
> > > > > >     }
> > > > > > -   if (drm_dp_mst_atomic_check(state))
> > > > > > -           return false;
> > > > > > +   ret = drm_dp_mst_atomic_check(state);
> > > > > > +   if (ret != 0)
> > > > > > +           return ret;
> > > > > >
> > > > > >     /* Optimize degree of compression */
> > > > > > -   if (!increase_dsc_bpp(state, mst_state, dc_link, params, vars, count,
> > > > > > k))
> > > > > > -           return false;
> > > > > > +   ret = increase_dsc_bpp(state, mst_state, dc_link, params, vars,
> > > > > > count, k);
> > > > > > +   if (ret < 0)
> > > > > > +           return ret;
> > > > > >
> > > > > > -   if (!try_disable_dsc(state, dc_link, params, vars, count, k))
> > > > > > -           return false;
> > > > > > +   ret = try_disable_dsc(state, dc_link, params, vars, count, k);
> > > > > > +   if (ret < 0)
> > > > > > +           return ret;
> > > > > >
> > > > > >     set_dsc_configs_from_fairness_vars(params, vars, count, k);
> > > > > >
> > > > > > -   return true;
> > > > > > +   return 0;
> > > > > >  }
> > > > > >
> > > > > >  static bool is_dsc_need_re_compute(
> > > > > > @@ -1087,15 +1109,16 @@ static bool is_dsc_need_re_compute(
> > > > > >     return is_dsc_need_re_compute;
> > > > > >  }
> > > > > >
> > > > > > -bool compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> > > > > > -                                  struct dc_state *dc_state,
> > > > > > -                                  struct dsc_mst_fairness_vars *vars)
> > > > > > +int compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> > > > > > +                                 struct dc_state *dc_state,
> > > > > > +                                 struct dsc_mst_fairness_vars *vars)
> > > > > >  {
> > > > > >     int i, j;
> > > > > >     struct dc_stream_state *stream;
> > > > > >     bool computed_streams[MAX_PIPES];
> > > > > >     struct amdgpu_dm_connector *aconnector;
> > > > > >     int link_vars_start_index = 0;
> > > > > > +   int ret = 0;
> > > > > >
> > > > > >     for (i = 0; i < dc_state->stream_count; i++)
> > > > > >             computed_streams[i] = false;
> > > > > > @@ -1118,17 +1141,19 @@ bool compute_mst_dsc_configs_for_state(struct
> > > > > > drm_atomic_state *state,
> > > > > >                     continue;
> > > > > >
> > > > > >             if (dcn20_remove_stream_from_ctx(stream->ctx->dc,
> > > > > > dc_state, stream) != DC_OK)
> > > > > > -                   return false;
> > > > > > +                   return -EINVAL;
> > > > > >
> > > > > >             if (!is_dsc_need_re_compute(state, dc_state, stream->link))
> > > > > >                     continue;
> > > > > >
> > > > > >             mutex_lock(&aconnector->mst_mgr.lock);
> > > > > > -           if (!compute_mst_dsc_configs_for_link(state, dc_state,
> > > > > > stream->link, vars,
> > > > > > -                                                 &aconnector->mst_mgr,
> > > > > > -                                                 &link_vars_start_index)) {
> > > > > > +
> > > > > > +           ret = compute_mst_dsc_configs_for_link(state, dc_state,
> > > > > > stream->link, vars,
> > > > > > +                                                  &aconnector->mst_mgr,
> > > > > > +                                                  &link_vars_start_index);
> > > > > > +           if (ret != 0) {
> > > > > >                     mutex_unlock(&aconnector->mst_mgr.lock);
> > > > > > -                   return false;
> > > > > > +                   return ret;
> > > > > >             }
> > > > > >             mutex_unlock(&aconnector->mst_mgr.lock);
> > > > > >
> > > > > > @@ -1143,22 +1168,22 @@ bool compute_mst_dsc_configs_for_state(struct
> > > > > > drm_atomic_state *state,
> > > > > >
> > > > > >             if (stream->timing.flags.DSC == 1)
> > > > > >                     if (dc_stream_add_dsc_to_resource(stream->ctx-
> > > > > > > dc, dc_state, stream) != DC_OK)
> > > > > > -                           return false;
> > > > > > +                           return -EINVAL;
> > > > > >     }
> > > > > >
> > > > > > -   return true;
> > > > > > +   return ret;
> > > > > >  }
> > > > > >
> > > > > > -static bool
> > > > > > -   pre_compute_mst_dsc_configs_for_state(struct drm_atomic_state
> > > > > > *state,
> > > > > > -                                         struct dc_state *dc_state,
> > > > > > -                                         struct dsc_mst_fairness_vars
> > > > > > *vars)
> > > > > > +static int pre_compute_mst_dsc_configs_for_state(struct
> > > > > > drm_atomic_state *state,
> > > > > > +                                            struct dc_state *dc_state,
> > > > > > +                                            struct dsc_mst_fairness_vars
> > > > > > *vars)
> > > > > >  {
> > > > > >     int i, j;
> > > > > >     struct dc_stream_state *stream;
> > > > > >     bool computed_streams[MAX_PIPES];
> > > > > >     struct amdgpu_dm_connector *aconnector;
> > > > > >     int link_vars_start_index = 0;
> > > > > > +   int ret;
> > > > > >
> > > > > >     for (i = 0; i < dc_state->stream_count; i++)
> > > > > >             computed_streams[i] = false;
> > > > > > @@ -1184,11 +1209,12 @@ static bool
> > > > > >                     continue;
> > > > > >
> > > > > >             mutex_lock(&aconnector->mst_mgr.lock);
> > > > > > -           if (!compute_mst_dsc_configs_for_link(state, dc_state,
> > > > > > stream->link, vars,
> > > > > > -                                                 &aconnector->mst_mgr,
> > > > > > -                                                 &link_vars_start_index)) {
> > > > > > +           ret = compute_mst_dsc_configs_for_link(state, dc_state,
> > > > > > stream->link, vars,
> > > > > > +                                                  &aconnector->mst_mgr,
> > > > > > +                                                  &link_vars_start_index);
> > > > > > +           if (ret != 0) {
> > > > > >                     mutex_unlock(&aconnector->mst_mgr.lock);
> > > > > > -                   return false;
> > > > > > +                   return ret;
> > > > > >             }
> > > > > >             mutex_unlock(&aconnector->mst_mgr.lock);
> > > > > >
> > > > > > @@ -1198,7 +1224,7 @@ static bool
> > > > > >             }
> > > > > >     }
> > > > > >
> > > > > > -   return true;
> > > > > > +   return ret;
> > > > > >  }
> > > > > >
> > > > > >  static int find_crtc_index_in_state_by_stream(struct drm_atomic_state
> > > > > > *state, @@ -1253,9 +1279,9 @@ static bool
> > > > > > is_dsc_precompute_needed(struct drm_atomic_state *state)
> > > > > >     return ret;
> > > > > >  }
> > > > > >
> > > > > > -bool pre_validate_dsc(struct drm_atomic_state *state,
> > > > > > -                 struct dm_atomic_state **dm_state_ptr,
> > > > > > -                 struct dsc_mst_fairness_vars *vars)
> > > > > > +int pre_validate_dsc(struct drm_atomic_state *state,
> > > > > > +                struct dm_atomic_state **dm_state_ptr,
> > > > > > +                struct dsc_mst_fairness_vars *vars)
> > > > > >  {
> > > > > >     int i;
> > > > > >     struct dm_atomic_state *dm_state;
> > > > > > @@ -1264,11 +1290,12 @@ bool pre_validate_dsc(struct drm_atomic_state
> > > > > > *state,
> > > > > >
> > > > > >     if (!is_dsc_precompute_needed(state)) {
> > > > > >             DRM_INFO_ONCE("DSC precompute is not needed.\n");
> > > > > > -           return true;
> > > > > > +           return 0;
> > > > > >     }
> > > > > > -   if (dm_atomic_get_state(state, dm_state_ptr)) {
> > > > > > +   ret = dm_atomic_get_state(state, dm_state_ptr);
> > > > > > +   if (ret != 0) {
> > > > > >             DRM_INFO_ONCE("dm_atomic_get_state() failed\n");
> > > > > > -           return false;
> > > > > > +           return ret;
> > > > > >     }
> > > > > >     dm_state = *dm_state_ptr;
> > > > > >
> > > > > > @@ -1280,7 +1307,7 @@ bool pre_validate_dsc(struct drm_atomic_state
> > > > > > *state,
> > > > > >
> > > > > >     local_dc_state = kmemdup(dm_state->context, sizeof(struct
> > > > > > dc_state), GFP_KERNEL);
> > > > > >     if (!local_dc_state)
> > > > > > -           return false;
> > > > > > +           return -ENOMEM;
> > > > > >
> > > > > >     for (i = 0; i < local_dc_state->stream_count; i++) {
> > > > > >             struct dc_stream_state *stream = dm_state->context-
> > > > > > > streams[i]; @@ -1316,9 +1343,9 @@ bool pre_validate_dsc(struct
> > > > > > drm_atomic_state *state,
> > > > > >     if (ret != 0)
> > > > > >             goto clean_exit;
> > > > > >
> > > > > > -   if (!pre_compute_mst_dsc_configs_for_state(state, local_dc_state,
> > > > > > vars)) {
> > > > > > +   ret = pre_compute_mst_dsc_configs_for_state(state, local_dc_state,
> > > > > > vars);
> > > > > > +   if (ret != 0) {
> > > > > >
> > > > > >     DRM_INFO_ONCE("pre_compute_mst_dsc_configs_for_state()
> > > > > > failed\n");
> > > > > > -           ret = -EINVAL;
> > > > > >             goto clean_exit;
> > > > > >     }
> > > > > >
> > > > > > @@ -1349,7 +1376,7 @@ bool pre_validate_dsc(struct drm_atomic_state
> > > > > > *state,
> > > > > >
> > > > > >     kfree(local_dc_state);
> > > > > >
> > > > > > -   return (ret == 0);
> > > > > > +   return ret;
> > > > > >  }
> > > > > >
> > > > > >  static unsigned int kbps_from_pbn(unsigned int pbn) diff --git
> > > > > > a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> > > > > > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> > > > > > index b92a7c5671aa2..97fd70df531bf 100644
> > > > > > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> > > > > > +++
> > > > > > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> > > > > > @@ -53,15 +53,15 @@ struct dsc_mst_fairness_vars {
> > > > > >     struct amdgpu_dm_connector *aconnector;  };
> > > > > >
> > > > > > -bool compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> > > > > > -                                  struct dc_state *dc_state,
> > > > > > -                                  struct dsc_mst_fairness_vars *vars);
> > > > > > +int compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> > > > > > +                                 struct dc_state *dc_state,
> > > > > > +                                 struct dsc_mst_fairness_vars *vars);
> > > > > >
> > > > > >  bool needs_dsc_aux_workaround(struct dc_link *link);
> > > > > >
> > > > > > -bool pre_validate_dsc(struct drm_atomic_state *state,
> > > > > > -                 struct dm_atomic_state **dm_state_ptr,
> > > > > > -                 struct dsc_mst_fairness_vars *vars);
> > > > > > +int pre_validate_dsc(struct drm_atomic_state *state,
> > > > > > +                struct dm_atomic_state **dm_state_ptr,
> > > > > > +                struct dsc_mst_fairness_vars *vars);
> > > > > >
> > > > > >  enum dc_status dm_dp_mst_is_port_support_mode(
> > > > > >     struct amdgpu_dm_connector *aconnector,
> > > > > > --
> > > > > > 2.37.3
> > > > >
> > > >
> > > > --
> > > > Cheers,
> > > >  Lyude Paul (she/her)
> > > >  Software Engineer at Red Hat
> > > >
> > >
> >
>
> --
> Cheers,
>  Lyude Paul (she/her)
>  Software Engineer at Red Hat
>