diff mbox series

[v2,net-next,1/9] net: enetc: fix MAC Merge layer remaining enabled until a link down event

Message ID 20230418111459.811553-2-vladimir.oltean@nxp.com
State New
Headers
Series ethtool mm API consolidation |

Commit Message

Vladimir Oltean April 18, 2023, 11:14 a.m. UTC 
  Current enetc_set_mm() is designed to set the priv->active_offloads bit
ENETC_F_QBU for enetc_mm_link_state_update() to act on, but if the link
is already up, it modifies the ENETC_MMCSR_ME ("Merge Enable") bit
directly.

The problem is that it only *sets* ENETC_MMCSR_ME if the link is up, it
doesn't *clear* it if needed. So subsequent enetc_get_mm() calls still
see tx-enabled as true, up until a link down event, which is when
enetc_mm_link_state_update() will get called.

This is not a functional issue as far as I can assess. It has only come
up because I'd like to uphold a simple API rule in core ethtool code:
the pMAC cannot be disabled if TX is going to be enabled. Currently,
the fact that TX remains enabled for longer than expected (after the
enetc_set_mm() call that disables it) is going to violate that rule,
which is how it was caught.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
v1->v2: none

 drivers/net/ethernet/freescale/enetc/enetc_ethtool.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

Comments

Simon Horman April 20, 2023, 2:22 p.m. UTC | #1 
On Tue, Apr 18, 2023 at 02:14:51PM +0300, Vladimir Oltean wrote:
> Current enetc_set_mm() is designed to set the priv->active_offloads bit
> ENETC_F_QBU for enetc_mm_link_state_update() to act on, but if the link
> is already up, it modifies the ENETC_MMCSR_ME ("Merge Enable") bit
> directly.
> 
> The problem is that it only *sets* ENETC_MMCSR_ME if the link is up, it
> doesn't *clear* it if needed. So subsequent enetc_get_mm() calls still
> see tx-enabled as true, up until a link down event, which is when
> enetc_mm_link_state_update() will get called.
> 
> This is not a functional issue as far as I can assess. It has only come
> up because I'd like to uphold a simple API rule in core ethtool code:
> the pMAC cannot be disabled if TX is going to be enabled. Currently,
> the fact that TX remains enabled for longer than expected (after the
> enetc_set_mm() call that disables it) is going to violate that rule,
> which is how it was caught.
> 
> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>

Reviewed-by: Simon Horman <simon.horman@corigine.com>

> ---
> v1->v2: none
> 
>  drivers/net/ethernet/freescale/enetc/enetc_ethtool.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/net/ethernet/freescale/enetc/enetc_ethtool.c b/drivers/net/ethernet/freescale/enetc/enetc_ethtool.c
> index 838750a03cf6..ee1ea71fe79e 100644
> --- a/drivers/net/ethernet/freescale/enetc/enetc_ethtool.c
> +++ b/drivers/net/ethernet/freescale/enetc/enetc_ethtool.c
> @@ -1041,10 +1041,13 @@ static int enetc_set_mm(struct net_device *ndev, struct ethtool_mm_cfg *cfg,
>  	else
>  		priv->active_offloads &= ~ENETC_F_QBU;
>  
> -	/* If link is up, enable MAC Merge right away */
> -	if (!!(priv->active_offloads & ENETC_F_QBU) &&
> -	    !(val & ENETC_MMCSR_LINK_FAIL))
> -		val |= ENETC_MMCSR_ME;
> +	/* If link is up, enable/disable MAC Merge right away */
> +	if (!(val & ENETC_MMCSR_LINK_FAIL)) {
> +		if (!!(priv->active_offloads & ENETC_F_QBU))

nit: The !!() seems unnecessary,
     I wonder if it can be written in a simpler way as:

		if (priv->active_offloads & ENETC_F_QBU)

> +			val |= ENETC_MMCSR_ME;
> +		else
> +			val &= ~ENETC_MMCSR_ME;
> +	}
>  
>  	val &= ~ENETC_MMCSR_VT_MASK;
>  	val |= ENETC_MMCSR_VT(cfg->verify_time);
> -- 
> 2.34.1
>
Vladimir Oltean April 20, 2023, 5:03 p.m. UTC | #2 
On Thu, Apr 20, 2023 at 04:22:04PM +0200, Simon Horman wrote:
> > -	/* If link is up, enable MAC Merge right away */
> > -	if (!!(priv->active_offloads & ENETC_F_QBU) &&
> > -	    !(val & ENETC_MMCSR_LINK_FAIL))
> > -		val |= ENETC_MMCSR_ME;
> > +	/* If link is up, enable/disable MAC Merge right away */
> > +	if (!(val & ENETC_MMCSR_LINK_FAIL)) {
> > +		if (!!(priv->active_offloads & ENETC_F_QBU))
> 
> nit: The !!() seems unnecessary,
>      I wonder if it can be written in a simpler way as:
> 
> 		if (priv->active_offloads & ENETC_F_QBU)

I agree. Normally I omit the double negation in simple statements like this.
Here I didn't, because the expression was split into 2 "if" conditions,
and I kept the individual terms as-is for some reason.

Since the generated object code is absolutely the same either way, I would not
resend just for minor style comments such as this one, if you don't mind.
However, I do appreciate the review and I'll pay more attention to this
detail in the future.
Simon Horman April 21, 2023, 9:01 a.m. UTC | #3 
On Thu, Apr 20, 2023 at 08:03:54PM +0300, Vladimir Oltean wrote:
> On Thu, Apr 20, 2023 at 04:22:04PM +0200, Simon Horman wrote:
> > > -	/* If link is up, enable MAC Merge right away */
> > > -	if (!!(priv->active_offloads & ENETC_F_QBU) &&
> > > -	    !(val & ENETC_MMCSR_LINK_FAIL))
> > > -		val |= ENETC_MMCSR_ME;
> > > +	/* If link is up, enable/disable MAC Merge right away */
> > > +	if (!(val & ENETC_MMCSR_LINK_FAIL)) {
> > > +		if (!!(priv->active_offloads & ENETC_F_QBU))
> > 
> > nit: The !!() seems unnecessary,
> >      I wonder if it can be written in a simpler way as:
> > 
> > 		if (priv->active_offloads & ENETC_F_QBU)
> 
> I agree. Normally I omit the double negation in simple statements like this.
> Here I didn't, because the expression was split into 2 "if" conditions,
> and I kept the individual terms as-is for some reason.
> 
> Since the generated object code is absolutely the same either way, I would not
> resend just for minor style comments such as this one, if you don't mind.
> However, I do appreciate the review and I'll pay more attention to this
> detail in the future.

Thanks. I agree the result should be same.
No need to resend because of this.
diff mbox series

Patch

diff --git a/drivers/net/ethernet/freescale/enetc/enetc_ethtool.c b/drivers/net/ethernet/freescale/enetc/enetc_ethtool.c
index 838750a03cf6..ee1ea71fe79e 100644
--- a/drivers/net/ethernet/freescale/enetc/enetc_ethtool.c
+++ b/drivers/net/ethernet/freescale/enetc/enetc_ethtool.c
@@ -1041,10 +1041,13 @@  static int enetc_set_mm(struct net_device *ndev, struct ethtool_mm_cfg *cfg,
 	else
 		priv->active_offloads &= ~ENETC_F_QBU;
 
-	/* If link is up, enable MAC Merge right away */
-	if (!!(priv->active_offloads & ENETC_F_QBU) &&
-	    !(val & ENETC_MMCSR_LINK_FAIL))
-		val |= ENETC_MMCSR_ME;
+	/* If link is up, enable/disable MAC Merge right away */
+	if (!(val & ENETC_MMCSR_LINK_FAIL)) {
+		if (!!(priv->active_offloads & ENETC_F_QBU))
+			val |= ENETC_MMCSR_ME;
+		else
+			val &= ~ENETC_MMCSR_ME;
+	}
 
 	val &= ~ENETC_MMCSR_VT_MASK;
 	val |= ENETC_MMCSR_VT(cfg->verify_time);