netdev - Re: [PATCH] net: dsa: mv88e6060: report max mtu 1536

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Date:   Wed, 10 Aug 2022 13:08:18 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Sergei Antonov <saproj@...il.com>
Cc:     netdev@...r.kernel.org, Florian Fainelli <f.fainelli@...il.com>
Subject: Re: [PATCH] net: dsa: mv88e6060: report max mtu 1536

Hi Sergei,

On Wed, Aug 10, 2022 at 11:27:45AM +0300, Sergei Antonov wrote:
> This driver sets the MaxFrameSize bit to 1 during setup,
> see GLOBAL_CONTROL_MAX_FRAME_1536 in mv88e6060_setup_global().
> Thus MTU is always 1536.
> Introduce mv88e6060_port_max_mtu() to report it back to system.
> 
> Signed-off-by: Sergei Antonov <saproj@...il.com>
> CC: Vladimir Oltean <olteanv@...il.com>
> CC: Florian Fainelli <f.fainelli@...il.com>
> ---
>  drivers/net/dsa/mv88e6060.c | 7 ++++++-
>  drivers/net/dsa/mv88e6060.h | 1 +
>  2 files changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/dsa/mv88e6060.c b/drivers/net/dsa/mv88e6060.c
> index a4c6eb9a52d0..c53734379b96 100644
> --- a/drivers/net/dsa/mv88e6060.c
> +++ b/drivers/net/dsa/mv88e6060.c
> @@ -160,7 +160,6 @@ static int mv88e6060_setup_addr(struct mv88e6060_priv *priv)
>  	u16 val;
>  
>  	eth_random_addr(addr);
> -

Extraneous change.

>  	val = addr[0] << 8 | addr[1];
>  
>  	/* The multicast bit is always transmitted as a zero, so the switch uses
> @@ -212,6 +211,11 @@ static int mv88e6060_setup(struct dsa_switch *ds)
>  	return 0;
>  }
>  
> +static int mv88e6060_port_max_mtu(struct dsa_switch *ds, int port)
> +{
> +	return MV88E6060_MAX_MTU;
> +}

Does this solve any problem? It's ok for the hardware MTU to be higher
than advertised. The problem is when the hardware doesn't accept what
the stack thinks it should.

> +
>  static int mv88e6060_port_to_phy_addr(int port)
>  {
>  	if (port >= 0 && port < MV88E6060_PORTS)
> @@ -247,6 +251,7 @@ mv88e6060_phy_write(struct dsa_switch *ds, int port, int regnum, u16 val)
>  static const struct dsa_switch_ops mv88e6060_switch_ops = {
>  	.get_tag_protocol = mv88e6060_get_tag_protocol,
>  	.setup		= mv88e6060_setup,
> +	.port_max_mtu	= mv88e6060_port_max_mtu,
>  	.phy_read	= mv88e6060_phy_read,
>  	.phy_write	= mv88e6060_phy_write,
>  };
> diff --git a/drivers/net/dsa/mv88e6060.h b/drivers/net/dsa/mv88e6060.h
> index 6c13c2421b64..382fe462fb2d 100644
> --- a/drivers/net/dsa/mv88e6060.h
> +++ b/drivers/net/dsa/mv88e6060.h
> @@ -11,6 +11,7 @@
>  #define __MV88E6060_H
>  
>  #define MV88E6060_PORTS	6
> +#define MV88E6060_MAX_MTU	1536
>  
>  #define REG_PORT(p)		(0x8 + (p))
>  #define PORT_STATUS		0x00
> -- 
> 2.32.0
> 

You're the first person to submit a patch on mv88e6060 that I see.
Is there a board with this switch available somewhere? Does the driver
still work?