[net-next,v3,3/3] net: dsa: rzn1-a5psw: add vlan support

  Add support for vlan operation (add, del, filtering) on the RZN1
driver. The a5psw switch supports up to 32 VLAN IDs with filtering,
tagged/untagged VLANs and PVID for each ports.

Signed-off-by: Clément Léger <clement.leger@bootlin.com>
---
 drivers/net/dsa/rzn1_a5psw.c | 167 +++++++++++++++++++++++++++++++++++
 drivers/net/dsa/rzn1_a5psw.h |   8 +-
 2 files changed, 172 insertions(+), 3 deletions(-)
  

On 2/8/23 08:17, Clément Léger wrote:
> Add support for vlan operation (add, del, filtering) on the RZN1
> driver. The a5psw switch supports up to 32 VLAN IDs with filtering,
> tagged/untagged VLANs and PVID for each ports.
> 
> Signed-off-by: Clément Léger <clement.leger@bootlin.com>

This looks good to me, just a few nits/suggestions below.

> ---
>   drivers/net/dsa/rzn1_a5psw.c | 167 +++++++++++++++++++++++++++++++++++
>   drivers/net/dsa/rzn1_a5psw.h |   8 +-
>   2 files changed, 172 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/dsa/rzn1_a5psw.c b/drivers/net/dsa/rzn1_a5psw.c
> index 0ce3948952db..de6b18ec647d 100644
> --- a/drivers/net/dsa/rzn1_a5psw.c
> +++ b/drivers/net/dsa/rzn1_a5psw.c
> @@ -583,6 +583,147 @@ static int a5psw_port_fdb_dump(struct dsa_switch *ds, int port,
>   	return ret;
>   }
>   
> +static int a5psw_port_vlan_filtering(struct dsa_switch *ds, int port,
> +				     bool vlan_filtering,
> +				     struct netlink_ext_ack *extack)
> +{
> +	u32 mask = BIT(port + A5PSW_VLAN_VERI_SHIFT) |
> +		   BIT(port + A5PSW_VLAN_DISC_SHIFT);
> +	struct a5psw *a5psw = ds->priv;
> +	u32 val = 0;
> +
> +	if (vlan_filtering)
> +		val = BIT(port + A5PSW_VLAN_VERI_SHIFT) |
> +		      BIT(port + A5PSW_VLAN_DISC_SHIFT);
> +
> +	a5psw_reg_rmw(a5psw, A5PSW_VLAN_VERIFY, mask, val);
> +
> +	return 0;
> +}
> +
> +static int a5psw_find_vlan_entry(struct a5psw *a5psw, u16 vid)
> +{
> +	u32 vlan_res;
> +	int i;
> +
> +	/* Find vlan for this port */
> +	for (i = 0; i < A5PSW_VLAN_COUNT; i++) {
> +		vlan_res = a5psw_reg_readl(a5psw, A5PSW_VLAN_RES(i));
> +		if (FIELD_GET(A5PSW_VLAN_RES_VLANID, vlan_res) == vid)
> +			return i;
> +	}
> +
> +	return -1;
> +}
> +
> +static int a5psw_get_vlan_res_entry(struct a5psw *a5psw, u16 newvid)

The name seems a bit misleading with respect to what it does, maybe 
a5psw_new_vlan_res_entry()?

> +{
> +	u32 vlan_res;
> +	int i;
> +
> +	/* Find a free VLAN entry */
> +	for (i = 0; i < A5PSW_VLAN_COUNT; i++) {
> +		vlan_res = a5psw_reg_readl(a5psw, A5PSW_VLAN_RES(i));
> +		if (!(FIELD_GET(A5PSW_VLAN_RES_PORTMASK, vlan_res))) {
> +			vlan_res = FIELD_PREP(A5PSW_VLAN_RES_VLANID, newvid);
> +			a5psw_reg_writel(a5psw, A5PSW_VLAN_RES(i), vlan_res);
> +			return i;
> +		}
> +	}
> +
> +	return -1;
> +}
> +
> +static void a5psw_port_vlan_tagged_cfg(struct a5psw *a5psw, int vlan_res_id,

unsigned int vlan_res_id

> +				       int port, bool set)
> +{
> +	u32 mask = A5PSW_VLAN_RES_WR_PORTMASK | A5PSW_VLAN_RES_RD_TAGMASK |
> +		   BIT(port);
> +	u32 vlan_res_off = A5PSW_VLAN_RES(vlan_res_id);
> +	u32 val = A5PSW_VLAN_RES_WR_TAGMASK, reg;
> +
> +	if (set)
> +		val |= BIT(port);
> +
> +	/* Toggle tag mask read */
> +	a5psw_reg_writel(a5psw, vlan_res_off, A5PSW_VLAN_RES_RD_TAGMASK);
> +	reg = a5psw_reg_readl(a5psw, vlan_res_off);
> +	a5psw_reg_writel(a5psw, vlan_res_off, A5PSW_VLAN_RES_RD_TAGMASK);
> +
> +	reg &= ~mask;
> +	reg |= val;
> +	a5psw_reg_writel(a5psw, vlan_res_off, reg);
> +}
> +
> +static void a5psw_port_vlan_cfg(struct a5psw *a5psw, int vlan_res_id, int port,

Likewise

> +				bool set)
> +{
> +	u32 mask = A5PSW_VLAN_RES_WR_TAGMASK | BIT(port);
> +	u32 reg = A5PSW_VLAN_RES_WR_PORTMASK;
> +
> +	if (set)
> +		reg |= BIT(port);
> +
> +	a5psw_reg_rmw(a5psw, A5PSW_VLAN_RES(vlan_res_id), mask, reg);
> +}
> +
> +static int a5psw_port_vlan_add(struct dsa_switch *ds, int port,
> +			       const struct switchdev_obj_port_vlan *vlan,
> +			       struct netlink_ext_ack *extack)
> +{
> +	bool tagged = !(vlan->flags & BRIDGE_VLAN_INFO_UNTAGGED);
> +	bool pvid = vlan->flags & BRIDGE_VLAN_INFO_PVID;
> +	struct a5psw *a5psw = ds->priv;
> +	u16 vid = vlan->vid;
> +	int vlan_res_id;
> +
> +	dev_dbg(a5psw->dev, "Add VLAN %d on port %d, %s, %s\n",
> +		vid, port, tagged ? "tagged" : "untagged",
> +		pvid ? "PVID" : "no PVID");
> +
> +	vlan_res_id = a5psw_find_vlan_entry(a5psw, vid);
> +	if (vlan_res_id < 0) {
> +		vlan_res_id = a5psw_get_vlan_res_entry(a5psw, vid);
> +		if (vlan_res_id < 0)
> +			return -EINVAL;

return -ENOSPC?

> +	}
> +
> +	a5psw_port_vlan_cfg(a5psw, vlan_res_id, port, true);
> +	if (tagged)
> +		a5psw_port_vlan_tagged_cfg(a5psw, vlan_res_id, port, true);
> +
> +	if (pvid) {
> +		a5psw_reg_rmw(a5psw, A5PSW_VLAN_IN_MODE_ENA, BIT(port),
> +			      BIT(port));
> +		a5psw_reg_writel(a5psw, A5PSW_SYSTEM_TAGINFO(port), vid);
> +	}
> +
> +	return 0;
> +}
> +
> +static int a5psw_port_vlan_del(struct dsa_switch *ds, int port,
> +			       const struct switchdev_obj_port_vlan *vlan)
> +{
> +	struct a5psw *a5psw = ds->priv;
> +	u16 vid = vlan->vid;
> +	int vlan_res_id;
> +
> +	dev_dbg(a5psw->dev, "Removing VLAN %d on port %d\n", vid, port);
> +
> +	vlan_res_id = a5psw_find_vlan_entry(a5psw, vid);
> +	if (vlan_res_id < 0)
> +		return -EINVAL;

-EINVAL looks legit here

> +
> +	a5psw_port_vlan_cfg(a5psw, vlan_res_id, port, false);
> +	a5psw_port_vlan_tagged_cfg(a5psw, vlan_res_id, port, false);
> +
> +	/* Disable PVID if the vid is matching the port one */
> +	if (vid == a5psw_reg_readl(a5psw, A5PSW_SYSTEM_TAGINFO(port)))
> +		a5psw_reg_rmw(a5psw, A5PSW_VLAN_IN_MODE_ENA, BIT(port), 0);
> +
> +	return 0;
> +}
> +
>   static u64 a5psw_read_stat(struct a5psw *a5psw, u32 offset, int port)
>   {
>   	u32 reg_lo, reg_hi;
> @@ -700,6 +841,27 @@ static void a5psw_get_eth_ctrl_stats(struct dsa_switch *ds, int port,
>   	ctrl_stats->MACControlFramesReceived = stat;
>   }
>   
> +static void a5psw_vlan_setup(struct a5psw *a5psw, int port)
> +{
> +	u32 reg;
> +
> +	/* Enable TAG always mode for the port, this is actually controlled
> +	 * by VLAN_IN_MODE_ENA field which will be used for PVID insertion
> +	 */
> +	reg = A5PSW_VLAN_IN_MODE_TAG_ALWAYS;
> +	reg <<= A5PSW_VLAN_IN_MODE_PORT_SHIFT(port);
> +	a5psw_reg_rmw(a5psw, A5PSW_VLAN_IN_MODE, A5PSW_VLAN_IN_MODE_PORT(port),
> +		      reg);

If we always enable VLAN mode, which VLAN ID do switch ports not part of 
a VLAN aware bridge get classified into?

> +
> +	/* Set transparent mode for output frame manipulation, this will depend
> +	 * on the VLAN_RES configuration mode
> +	 */
> +	reg = A5PSW_VLAN_OUT_MODE_TRANSPARENT;
> +	reg <<= A5PSW_VLAN_OUT_MODE_PORT_SHIFT(port);
> +	a5psw_reg_rmw(a5psw, A5PSW_VLAN_OUT_MODE,
> +		      A5PSW_VLAN_OUT_MODE_PORT(port), reg);

Sort of a follow-on to the previous question, what does transparent 
mean? Does that mean the frames ingressing with a certain VLAN tag will 
egress with the same VLAN tag in the absence of a VLAN configuration 
rewriting the tag?

> +}
> +
>   static int a5psw_setup(struct dsa_switch *ds)
>   {
>   	struct a5psw *a5psw = ds->priv;
> @@ -772,6 +934,8 @@ static int a5psw_setup(struct dsa_switch *ds)
>   		/* Enable management forward only for user ports */
>   		if (dsa_port_is_user(dp))
>   			a5psw_port_mgmtfwd_set(a5psw, port, true);
> +
> +		a5psw_vlan_setup(a5psw, port);
>   	}
>   
>   	return 0;
> @@ -801,6 +965,9 @@ static const struct dsa_switch_ops a5psw_switch_ops = {
>   	.port_bridge_flags = a5psw_port_bridge_flags,
>   	.port_stp_state_set = a5psw_port_stp_state_set,
>   	.port_fast_age = a5psw_port_fast_age,
> +	.port_vlan_filtering = a5psw_port_vlan_filtering,
> +	.port_vlan_add = a5psw_port_vlan_add,
> +	.port_vlan_del = a5psw_port_vlan_del,
>   	.port_fdb_add = a5psw_port_fdb_add,
>   	.port_fdb_del = a5psw_port_fdb_del,
>   	.port_fdb_dump = a5psw_port_fdb_dump,
> diff --git a/drivers/net/dsa/rzn1_a5psw.h b/drivers/net/dsa/rzn1_a5psw.h
> index c67abd49c013..2bad2e3edc2a 100644
> --- a/drivers/net/dsa/rzn1_a5psw.h
> +++ b/drivers/net/dsa/rzn1_a5psw.h
> @@ -50,7 +50,9 @@
>   #define A5PSW_VLAN_IN_MODE_TAG_ALWAYS		0x2
>   
>   #define A5PSW_VLAN_OUT_MODE		0x2C
> -#define A5PSW_VLAN_OUT_MODE_PORT(port)	(GENMASK(1, 0) << ((port) * 2))
> +#define A5PSW_VLAN_OUT_MODE_PORT_SHIFT(port)	((port) * 2)
> +#define A5PSW_VLAN_OUT_MODE_PORT(port)	(GENMASK(1, 0) << \
> +					A5PSW_VLAN_OUT_MODE_PORT_SHIFT(port))
>   #define A5PSW_VLAN_OUT_MODE_DIS		0x0
>   #define A5PSW_VLAN_OUT_MODE_STRIP	0x1
>   #define A5PSW_VLAN_OUT_MODE_TAG_THROUGH	0x2
> @@ -59,7 +61,7 @@
>   #define A5PSW_VLAN_IN_MODE_ENA		0x30
>   #define A5PSW_VLAN_TAG_ID		0x34
>   
> -#define A5PSW_SYSTEM_TAGINFO(port)	(0x200 + A5PSW_PORT_OFFSET(port))
> +#define A5PSW_SYSTEM_TAGINFO(port)	(0x200 + 4 * (port))
>   
>   #define A5PSW_AUTH_PORT(port)		(0x240 + 4 * (port))
>   #define A5PSW_AUTH_PORT_AUTHORIZED	BIT(0)
> @@ -68,7 +70,7 @@
>   #define A5PSW_VLAN_RES_WR_PORTMASK	BIT(30)
>   #define A5PSW_VLAN_RES_WR_TAGMASK	BIT(29)
>   #define A5PSW_VLAN_RES_RD_TAGMASK	BIT(28)
> -#define A5PSW_VLAN_RES_ID		GENMASK(16, 5)
> +#define A5PSW_VLAN_RES_VLANID		GENMASK(16, 5)
>   #define A5PSW_VLAN_RES_PORTMASK		GENMASK(4, 0)
>   
>   #define A5PSW_RXMATCH_CONFIG(port)	(0x3e80 + 4 * (port))
  

On Wed, Feb 08, 2023 at 09:38:04AM -0800, Florian Fainelli wrote:
> > +	/* Enable TAG always mode for the port, this is actually controlled
> > +	 * by VLAN_IN_MODE_ENA field which will be used for PVID insertion
> > +	 */
> > +	reg = A5PSW_VLAN_IN_MODE_TAG_ALWAYS;
> > +	reg <<= A5PSW_VLAN_IN_MODE_PORT_SHIFT(port);
> > +	a5psw_reg_rmw(a5psw, A5PSW_VLAN_IN_MODE, A5PSW_VLAN_IN_MODE_PORT(port),
> > +		      reg);
> 
> If we always enable VLAN mode, which VLAN ID do switch ports not part of a
> VLAN aware bridge get classified into?

Good question. I'd guess 0, since otherwise, the VLAN-unaware FDB
entries added with a5psw_port_fdb_add() wouldn't work.

But the driver has to survive the following chain of commands, which, by
looking at the current code structure, it doesn't:

ip link add br0 type bridge vlan_filtering 0
ip link set swp0 master br0 # PVID should remain at a value chosen privately by the driver
bridge vlan add dev swp0 vid 100 pvid untagged # PVID should not change in hardware yet
ip link set br0 type bridge vlan_filtering 1 # PVID should change to 100 now
ip link set br0 type bridge vlan_filtering 0 # PVID should change to the value chosen by the driver

Essentially, what I'm saying is that VLANs added with "bridge vlan add"
should only be active while vlan_filtering=1.

If you search for "commit_pvid" in drivers/net/dsa, you'll find a number
of drivers which have a more elaborate code structure which allows the
commands above to work properly.
  

On Wed, Feb 08, 2023 at 05:17:49PM +0100, Clément Léger wrote:
> +static void a5psw_port_vlan_tagged_cfg(struct a5psw *a5psw, int vlan_res_id,
> +				       int port, bool set)
> +{
> +	u32 mask = A5PSW_VLAN_RES_WR_PORTMASK | A5PSW_VLAN_RES_RD_TAGMASK |
> +		   BIT(port);
> +	u32 vlan_res_off = A5PSW_VLAN_RES(vlan_res_id);
> +	u32 val = A5PSW_VLAN_RES_WR_TAGMASK, reg;
> +
> +	if (set)
> +		val |= BIT(port);
> +
> +	/* Toggle tag mask read */
> +	a5psw_reg_writel(a5psw, vlan_res_off, A5PSW_VLAN_RES_RD_TAGMASK);
> +	reg = a5psw_reg_readl(a5psw, vlan_res_off);
> +	a5psw_reg_writel(a5psw, vlan_res_off, A5PSW_VLAN_RES_RD_TAGMASK);

Is it intentional that this register is written twice?

> +
> +	reg &= ~mask;
> +	reg |= val;
> +	a5psw_reg_writel(a5psw, vlan_res_off, reg);
> +}
  

Hi Clement,
On Wed, 2023-02-08 at 17:17 +0100, Clément Léger wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you
> know the content is safe
> 
> Add support for vlan operation (add, del, filtering) on the RZN1
> driver. The a5psw switch supports up to 32 VLAN IDs with filtering,
> tagged/untagged VLANs and PVID for each ports.
> 
> Signed-off-by: Clément Léger <clement.leger@bootlin.com>
> ---
>  drivers/net/dsa/rzn1_a5psw.c | 167
> +++++++++++++++++++++++++++++++++++
>  drivers/net/dsa/rzn1_a5psw.h |   8 +-
>  2 files changed, 172 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/dsa/rzn1_a5psw.c
> b/drivers/net/dsa/rzn1_a5psw.c
> index 0ce3948952db..de6b18ec647d 100644
> --- a/drivers/net/dsa/rzn1_a5psw.c
> +++ b/drivers/net/dsa/rzn1_a5psw.c
> @@ -583,6 +583,147 @@ static int a5psw_port_fdb_dump(struct
> dsa_switch *ds, int port,
>         return ret;
>  }
> 
> +static int a5psw_port_vlan_filtering(struct dsa_switch *ds, int
> port,
> +                                    bool vlan_filtering,
> +                                    struct netlink_ext_ack *extack)
> +{
> +       u32 mask = BIT(port + A5PSW_VLAN_VERI_SHIFT) |
> +                  BIT(port + A5PSW_VLAN_DISC_SHIFT);

nit: if initialization of mask is separated from declaration may
increase the readability.

> +       struct a5psw *a5psw = ds->priv;
> +       u32 val = 0;
> +
> +       if (vlan_filtering)
> +               val = BIT(port + A5PSW_VLAN_VERI_SHIFT) |
> +                     BIT(port + A5PSW_VLAN_DISC_SHIFT);
> +
> +       a5psw_reg_rmw(a5psw, A5PSW_VLAN_VERIFY, mask, val);
> +
> +       return 0;
> +}
> +
> +
> +static void a5psw_port_vlan_tagged_cfg(struct a5psw *a5psw, int
> vlan_res_id,
> +                                      int port, bool set)
> +{
> +       u32 mask = A5PSW_VLAN_RES_WR_PORTMASK |
> A5PSW_VLAN_RES_RD_TAGMASK |
> +                  BIT(port);

same here.

> +       u32 vlan_res_off = A5PSW_VLAN_RES(vlan_res_id);
> +       u32 val = A5PSW_VLAN_RES_WR_TAGMASK, reg;
> +
> +       if (set)
> +               val |= BIT(port);
> +
> +       /* Toggle tag mask read */
> +       a5psw_reg_writel(a5psw, vlan_res_off,
> A5PSW_VLAN_RES_RD_TAGMASK);
> +       reg = a5psw_reg_readl(a5psw, vlan_res_off);
> +       a5psw_reg_writel(a5psw, vlan_res_off,
> A5PSW_VLAN_RES_RD_TAGMASK+static int a5psw_port_vlan_add(struct
> dsa_switch *ds, int port,
> > +                              const struct switchdev_obj_port_vlan
> > *vlan,
> > +                              struct netlink_ext_ack *extack)
> > +{
> > +       bool tagged = !(vlan->flags & BRIDGE_VLAN_INFO_UNTAGGED);
> > +       bool pvid = vlan->flags & BRIDGE_VLAN_INFO_PVID;
> > +       struct a5psw *a5psw = ds->priv;
> > +       u16 vid = vlan->vid;
> > +       int vlan_res_id;
> > +
> > +       dev_dbg(a5psw->dev, "Add VLAN %d on port %d, %s, %s\n",
> > +               vid, port, tagged ? "tagged" : "untagged",
> > +               pvid ? "PVID" : "no PVID");
> > +
> > +       vlan_res_id = a5psw_find_vlan_entry(a5psw, vid);
> > +       if (vlan_res_id < 0) {
> > +               vlan_res_id = a5psw_get_vlan_res_entry(a5psw, vid);
> > +               if (vlan_res_id < 0)
> > +                       return -EINVAL;
> > +       }
> > +
> > +       a5psw_port_vlan_cfg(a5psw, vlan_res_id, port, true);
> > +       if (tagged)
> > +               a5psw_port_vlan_tagged_cfg(a5psw, vlan_res_id,
> port,
> > true);
> > +
> > +       if (pvid) {
> > +               a5psw_reg_rmw(a5psw, A5PSW_VLAN_IN_MODE_ENA,
> > BIT(port),
> > +                             BIT(port));
> > +               a5psw_reg_writel(a5psw, A5PSW_SYSTEM_TAGINFO(port),
> > vid);
> > +       }
> > +
> > +       return 0;
> > +}
> > +
>
  

Le Thu, 9 Feb 2023 00:02:19 +0200,
Vladimir Oltean <olteanv@gmail.com> a écrit :

> On Wed, Feb 08, 2023 at 09:38:04AM -0800, Florian Fainelli wrote:
> > > +	/* Enable TAG always mode for the port, this is actually controlled
> > > +	 * by VLAN_IN_MODE_ENA field which will be used for PVID insertion
> > > +	 */
> > > +	reg = A5PSW_VLAN_IN_MODE_TAG_ALWAYS;
> > > +	reg <<= A5PSW_VLAN_IN_MODE_PORT_SHIFT(port);
> > > +	a5psw_reg_rmw(a5psw, A5PSW_VLAN_IN_MODE, A5PSW_VLAN_IN_MODE_PORT(port),
> > > +		      reg);  
> > 
> > If we always enable VLAN mode, which VLAN ID do switch ports not part of a
> > VLAN aware bridge get classified into?  
> 
> Good question. I'd guess 0, since otherwise, the VLAN-unaware FDB
> entries added with a5psw_port_fdb_add() wouldn't work.

The name of the mode is probably missleading. When setting VLAN_IN_MODE
with A5PSW_VLAN_IN_MODE_TAG_ALWAYS, the input packet will be tagged
_only_ if VLAN_IN_MODE_ENA port bit is set. If this bit is not set,
packet will passthrough transparently. This bit is actually enabled in
a5psw_port_vlan_add() when a PVID is set and unset when the PVID is
removed. Maybe the comment above these lines was not clear enough.

> 
> But the driver has to survive the following chain of commands, which, by
> looking at the current code structure, it doesn't:
> 
> ip link add br0 type bridge vlan_filtering 0
> ip link set swp0 master br0 # PVID should remain at a value chosen privately by the driver
> bridge vlan add dev swp0 vid 100 pvid untagged # PVID should not change in hardware yet
> ip link set br0 type bridge vlan_filtering 1 # PVID should change to 100 now
> ip link set br0 type bridge vlan_filtering 0 # PVID should change to the value chosen by the driver
> 
> Essentially, what I'm saying is that VLANs added with "bridge vlan add"
> should only be active while vlan_filtering=1.
> 
> If you search for "commit_pvid" in drivers/net/dsa, you'll find a number
> of drivers which have a more elaborate code structure which allows the
> commands above to work properly.
  

Le Thu, 9 Feb 2023 00:03:09 +0200,
Vladimir Oltean <olteanv@gmail.com> a écrit :

> On Wed, Feb 08, 2023 at 05:17:49PM +0100, Clément Léger wrote:
> > +static void a5psw_port_vlan_tagged_cfg(struct a5psw *a5psw, int vlan_res_id,
> > +				       int port, bool set)
> > +{
> > +	u32 mask = A5PSW_VLAN_RES_WR_PORTMASK | A5PSW_VLAN_RES_RD_TAGMASK |
> > +		   BIT(port);
> > +	u32 vlan_res_off = A5PSW_VLAN_RES(vlan_res_id);
> > +	u32 val = A5PSW_VLAN_RES_WR_TAGMASK, reg;
> > +
> > +	if (set)
> > +		val |= BIT(port);
> > +
> > +	/* Toggle tag mask read */
> > +	a5psw_reg_writel(a5psw, vlan_res_off, A5PSW_VLAN_RES_RD_TAGMASK);
> > +	reg = a5psw_reg_readl(a5psw, vlan_res_off);
> > +	a5psw_reg_writel(a5psw, vlan_res_off, A5PSW_VLAN_RES_RD_TAGMASK);  
> 
> Is it intentional that this register is written twice?

Yes, the A5PSW_VLAN_RES_RD_TAGMASK bit is a toggle-bit (toggled
by writing a 1 in it) and it allows to read the tagmask (for
vlan tagging) instead of the portmask (for vlan membership):

"""
b28 read_tagmask:

Select contents of mask bits (4:0) when reading the
register. If this bit is set during a write into the register, all
other bits of the write are ignored (i.e. 30,29,16:0) and the bit 28 of
the register toggles (1-> 0; 0-> 1). This is used only to allow
changing the bit 28 without changing any table contents.
"""

> 
> > +
> > +	reg &= ~mask;
> > +	reg |= val;
> > +	a5psw_reg_writel(a5psw, vlan_res_off, reg);
> > +}
  

Le Wed, 8 Feb 2023 09:38:04 -0800,
Florian Fainelli <f.fainelli@gmail.com> a écrit :

> > +static void a5psw_vlan_setup(struct a5psw *a5psw, int port)
> > +{
> > +	u32 reg;
> > +
> > +	/* Enable TAG always mode for the port, this is actually controlled
> > +	 * by VLAN_IN_MODE_ENA field which will be used for PVID insertion
> > +	 */
> > +	reg = A5PSW_VLAN_IN_MODE_TAG_ALWAYS;
> > +	reg <<= A5PSW_VLAN_IN_MODE_PORT_SHIFT(port);
> > +	a5psw_reg_rmw(a5psw, A5PSW_VLAN_IN_MODE, A5PSW_VLAN_IN_MODE_PORT(port),
> > +		      reg);  
> 
> If we always enable VLAN mode, which VLAN ID do switch ports not part of 
> a VLAN aware bridge get classified into?

As answered on Vladimir question, it is VLAN_IN_MODE_ENAnot always VLAN enabled as
stated by the comment above but only if VLAN_IN_MODE_ENA is set (which
is done when setting a PVID only).

> 
> > +
> > +	/* Set transparent mode for output frame manipulation, this will depend
> > +	 * on the VLAN_RES configuration mode
> > +	 */
> > +	reg = A5PSW_VLAN_OUT_MODE_TRANSPARENT;
> > +	reg <<= A5PSW_VLAN_OUT_MODE_PORT_SHIFT(port);
> > +	a5psw_reg_rmw(a5psw, A5PSW_VLAN_OUT_MODE,
> > +		      A5PSW_VLAN_OUT_MODE_PORT(port), reg);  
> 
> Sort of a follow-on to the previous question, what does transparent 
> mean? Does that mean the frames ingressing with a certain VLAN tag will 
> egress with the same VLAN tag in the absence of a VLAN configuration 
> rewriting the tag?

Yes, here is an excerpt of the documentation which should clarified your
question (VLAN Table is actually stored in VLAN_RES registers):

- If frame’s VLAN id is found in the VLAN table (see Section
4.5.3.9(3)(b), VLAN Domain Resolution / VLAN Table) and the port is
defined as tagged for the VLAN, the frame is not modified.

- If frame’s VLAN id is found in the VLAN table and the port is defined
as untagged for the VLAN, the first VLAN tag is removed from the frame.

- If frame’s VLAN id is not found in the VLAN table, the frame is not
modified.

Thanks,