[PATCH net-next] net: dsa: mv88e6xxx: don't set non-existing learn2all bit for 6220/6250

[PATCH net-next] net: dsa: mv88e6xxx: don't set non-existing learn2all bit for 6220/6250

[Rasmus Villemoes]

The 6220 and 6250 switches do not have a learn2all bit in global1, ATU
control register; bit 3 is reserved.

On the switches that do have that bit, it is used to control whether
learning frames are sent out the ports that have the message_port bit
set. So rather than adding yet another chip method, use the existence
of the ->port_setup_message_port method as a proxy for determining
whether the learn2all bit exists (and should be set).

Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
---

This doesn't fix anything from what I can tell, in particular not the
VLAN problems I'm having, so just tagging for net-next. But I do think
it's worth it on the general principle of not poking around in
undocumented/reserved bits.

 drivers/net/dsa/mv88e6xxx/chip.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/net/dsa/mv88e6xxx/chip.c b/drivers/net/dsa/mv88e6xxx/chip.c
index 25449f634889..0245f3dfc1cd 100644
--- a/drivers/net/dsa/mv88e6xxx/chip.c
+++ b/drivers/net/dsa/mv88e6xxx/chip.c
@@ -1347,9 +1347,11 @@ static int mv88e6xxx_atu_setup(struct mv88e6xxx_chip *chip)
 	if (err)
 		return err;
 
-	err = mv88e6xxx_g1_atu_set_learn2all(chip, true);
-	if (err)
-		return err;
+	if (chip->info->ops->port_setup_message_port) {
+		err = mv88e6xxx_g1_atu_set_learn2all(chip, true);
+		if (err)
+			return err;
+	}
 
 	return mv88e6xxx_g1_atu_set_age_time(chip, 300000);
 }
-- 
2.23.0

Re: [PATCH net-next] net: dsa: mv88e6xxx: don't set non-existing learn2all bit for 6220/6250

[Andrew Lunn]

On Tue, Dec 08, 2020 at 10:01:09AM +0100, Rasmus Villemoes wrote:
> The 6220 and 6250 switches do not have a learn2all bit in global1, ATU
> control register; bit 3 is reserved.
> 
> On the switches that do have that bit, it is used to control whether
> learning frames are sent out the ports that have the message_port bit
> set. So rather than adding yet another chip method, use the existence
> of the ->port_setup_message_port method as a proxy for determining
> whether the learn2all bit exists (and should be set).
> 
> Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
> ---
> 
> This doesn't fix anything from what I can tell, in particular not the
> VLAN problems I'm having, so just tagging for net-next. But I do think
> it's worth it on the general principle of not poking around in
> undocumented/reserved bits.
> 
>  drivers/net/dsa/mv88e6xxx/chip.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/dsa/mv88e6xxx/chip.c b/drivers/net/dsa/mv88e6xxx/chip.c
> index 25449f634889..0245f3dfc1cd 100644
> --- a/drivers/net/dsa/mv88e6xxx/chip.c
> +++ b/drivers/net/dsa/mv88e6xxx/chip.c
> @@ -1347,9 +1347,11 @@ static int mv88e6xxx_atu_setup(struct mv88e6xxx_chip *chip)
>  	if (err)
>  		return err;
>  
> -	err = mv88e6xxx_g1_atu_set_learn2all(chip, true);
> -	if (err)
> -		return err;
> +	if (chip->info->ops->port_setup_message_port) {
> +		err = mv88e6xxx_g1_atu_set_learn2all(chip, true);
> +		if (err)
> +			return err;
> +	}

Hi Rasmus

This needs a comment in the code explaining why this odd structure is
used.

	Andrew

[PATCH net-next v2] net: dsa: mv88e6xxx: don't set non-existing learn2all bit for 6220/6250

[Rasmus Villemoes]

The 6220 and 6250 switches do not have a learn2all bit in global1, ATU
control register; bit 3 is reserverd.

On the switches that do have that bit, it is used to control whether
learning frames are sent out the ports that have the message_port bit
set. So rather than adding yet another chip method, use the existence
of the ->port_setup_message_port method as a proxy for determining
whether the learn2all bit exists (and should be set).

Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
---
v2: add comment explaining why ->port_setup_message_port is being used.

This doesn't fix anything from what I can tell, in particular not the
VLAN problems I'm having, so just tagging for net-next. But I do think
it's worth it on the general principle of not poking around in
undocumented/reserved bits.


 drivers/net/dsa/mv88e6xxx/chip.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/net/dsa/mv88e6xxx/chip.c b/drivers/net/dsa/mv88e6xxx/chip.c
index d68074a2f240..2068f2759fc9 100644
--- a/drivers/net/dsa/mv88e6xxx/chip.c
+++ b/drivers/net/dsa/mv88e6xxx/chip.c
@@ -1346,9 +1346,16 @@ static int mv88e6xxx_atu_setup(struct mv88e6xxx_chip *chip)
 	if (err)
 		return err;
 
-	err = mv88e6xxx_g1_atu_set_learn2all(chip, true);
-	if (err)
-		return err;
+	/* The chips that have a "learn2all" bit in Global1, ATU
+	 * Control are precisely those whose port registers have a
+	 * Message Port bit in Port Control 1 and hence implement
+	 * ->port_setup_message_port.
+	 */
+	if (chip->info->ops->port_setup_message_port) {
+		err = mv88e6xxx_g1_atu_set_learn2all(chip, true);
+		if (err)
+			return err;
+	}
 
 	return mv88e6xxx_g1_atu_set_age_time(chip, 300000);
 }
-- 
2.23.0

Re: [PATCH net-next v2] net: dsa: mv88e6xxx: don't set non-existing learn2all bit for 6220/6250

[Jakub Kicinski]

On Thu, 10 Dec 2020 12:06:44 +0100 Rasmus Villemoes wrote:
> The 6220 and 6250 switches do not have a learn2all bit in global1, ATU
> control register; bit 3 is reserverd.
> 
> On the switches that do have that bit, it is used to control whether
> learning frames are sent out the ports that have the message_port bit
> set. So rather than adding yet another chip method, use the existence
> of the ->port_setup_message_port method as a proxy for determining
> whether the learn2all bit exists (and should be set).
> 
> Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>

Applied.