netdev - Re: [PATCH v4 1/3] dsa: marvell: Provide per device information about max frame size

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Date:   Fri, 6 Jan 2023 16:51:09 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     Lukasz Majewski <lukma@...x.de>
Cc:     Andrew Lunn <andrew@...n.ch>, Eric Dumazet <edumazet@...gle.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Russell King <linux@...linux.org.uk>,
        Paolo Abeni <pabeni@...hat.com>,
        Alexander Duyck <alexander.duyck@...il.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/3] dsa: marvell: Provide per device information
 about max frame size

On Fri, Jan 06, 2023 at 11:16:49AM +0100, Lukasz Majewski wrote:
> Different Marvell DSA switches support different size of max frame
> bytes to be sent. This value corresponds to the memory allocated
> in switch to store single frame.
> 
> For example mv88e6185 supports max 1632 bytes, which is now in-driver
> standard value. On the other hand - mv88e6250 supports 2048 bytes.
> To be more interresting - devices supporting jumbo frames - use yet
> another value (10240 bytes)
> 
> As this value is internal and may be different for each switch IC,
> new entry in struct mv88e6xxx_info has been added to store it.
> 
> This commit doesn't change the code functionality - it just provides
> the max frame size value explicitly - up till now it has been
> assigned depending on the callback provided by the IC driver
> (e.g. .set_max_frame_size, .port_set_jumbo_size).
> 
> Signed-off-by: Lukasz Majewski <lukma@...x.de>
> 
> ---
> Changes for v2:
> - Define max_frame_size with default value of 1632 bytes,
> - Set proper value for the mv88e6250 switch SoC (linkstreet) family
> 
> Changes for v3:
> - Add default value for 1632B of the max frame size (to avoid problems
>   with not defined values)
> 
> Changes for v4:
> - Rework the mv88e6xxx_get_max_mtu() by using per device defined
>   max_frame_size value
> 
> - Add WARN_ON_ONCE() when max_frame_size is not defined
> 
> - Add description for the new 'max_frame_size' member of mv88e6xxx_info
> ---
>  drivers/net/dsa/mv88e6xxx/chip.c | 41 ++++++++++++++++++++++++++++----
>  drivers/net/dsa/mv88e6xxx/chip.h |  6 +++++
>  2 files changed, 42 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/net/dsa/mv88e6xxx/chip.c b/drivers/net/dsa/mv88e6xxx/chip.c
> index 242b8b325504..fc6d98c4a029 100644
> --- a/drivers/net/dsa/mv88e6xxx/chip.c
> +++ b/drivers/net/dsa/mv88e6xxx/chip.c
> @@ -3545,11 +3545,10 @@ static int mv88e6xxx_get_max_mtu(struct dsa_switch *ds, int port)
>  {
>  	struct mv88e6xxx_chip *chip = ds->priv;
>  
> -	if (chip->info->ops->port_set_jumbo_size)
> -		return 10240 - VLAN_ETH_HLEN - EDSA_HLEN - ETH_FCS_LEN;
> -	else if (chip->info->ops->set_max_frame_size)
> -		return 1632 - VLAN_ETH_HLEN - EDSA_HLEN - ETH_FCS_LEN;
> -	return 1522 - VLAN_ETH_HLEN - EDSA_HLEN - ETH_FCS_LEN;
> +	WARN_ON_ONCE(!chip->info->max_frame_size);
> +
> +	return chip->info->max_frame_size - VLAN_ETH_HLEN - EDSA_HLEN
> +		- ETH_FCS_LEN;

VLAN_ETH_HLEN (18) + EDSA_HLEN (8) + ETH_FCS_LEN (4) = 30

>  }
>  
>  static int mv88e6xxx_change_mtu(struct dsa_switch *ds, int port, int new_mtu)
> @@ -4955,6 +4954,7 @@ static const struct mv88e6xxx_ops mv88e6250_ops = {
>  	.avb_ops = &mv88e6352_avb_ops,
>  	.ptp_ops = &mv88e6250_ptp_ops,
>  	.phylink_get_caps = mv88e6250_phylink_get_caps,
> +	.set_max_frame_size = mv88e6185_g1_set_max_frame_size,
>  };
>  
>  static const struct mv88e6xxx_ops mv88e6290_ops = {
> @@ -5543,6 +5543,7 @@ static const struct mv88e6xxx_info mv88e6xxx_table[] = {
>  		.num_internal_phys = 5,
>  		.max_vid = 4095,
>  		.max_sid = 63,
> +		.max_frame_size = 1522,

1522 - 30 = 1492.

I don't believe that there are switches which don't support the standard
MTU of 1500 ?!

>  		.port_base_addr = 0x10,
>  		.phy_base_addr = 0x0,
>  		.global1_addr = 0x1b,

Note that I see this behavior isn't new. But I've simulated it, and it
will produce the following messages on probe:

[    7.425752] mscc_felix 0000:00:00.5 swp0 (uninitialized): PHY [0000:00:00.3:10] driver [Microsemi GE VSC8514 SyncE] (irq=POLL)
[    7.437516] mscc_felix 0000:00:00.5: nonfatal error -34 setting MTU to 1500 on port 0
[    7.588585] mscc_felix 0000:00:00.5 swp1 (uninitialized): PHY [0000:00:00.3:11] driver [Microsemi GE VSC8514 SyncE] (irq=POLL)
[    7.600433] mscc_felix 0000:00:00.5: nonfatal error -34 setting MTU to 1500 on port 1
[    7.752613] mscc_felix 0000:00:00.5 swp2 (uninitialized): PHY [0000:00:00.3:12] driver [Microsemi GE VSC8514 SyncE] (irq=POLL)
[    7.764457] mscc_felix 0000:00:00.5: nonfatal error -34 setting MTU to 1500 on port 2
[    7.900771] mscc_felix 0000:00:00.5 swp3 (uninitialized): PHY [0000:00:00.3:13] driver [Microsemi GE VSC8514 SyncE] (irq=POLL)
[    7.912501] mscc_felix 0000:00:00.5: nonfatal error -34 setting MTU to 1500 on port 3

I wonder, shouldn't we first fix that, and apply this patch set afterwards?