[PATCH net-next v2 1/1] net: macb: fix negative max_mtu size for sama5d3

[PATCH net-next v2 1/1] net: macb: fix negative max_mtu size for sama5d3

[Oleksij Rempel]

JML register on probe will return zero . This register is configured
later on macb_init_hw() which is called on open.
Since we have zero, after header and FCS length subtraction we will get
negative max_mtu size. This issue was affecting DSA drivers with MTU support
(for example KSZ9477).

Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
---
changes v2:
- properly describe fail reason
- simplify max_mtu logic

 drivers/net/ethernet/cadence/macb_main.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
index d89098f4ede8..d0ea8dbfa213 100644
--- a/drivers/net/ethernet/cadence/macb_main.c
+++ b/drivers/net/ethernet/cadence/macb_main.c
@@ -4913,8 +4913,8 @@ static int macb_probe(struct platform_device *pdev)
 
 	/* MTU range: 68 - 1500 or 10240 */
 	dev->min_mtu = GEM_MTU_MIN_SIZE;
-	if (bp->caps & MACB_CAPS_JUMBO)
-		dev->max_mtu = gem_readl(bp, JML) - ETH_HLEN - ETH_FCS_LEN;
+	if ((bp->caps & MACB_CAPS_JUMBO) && bp->jumbo_max_len)
+		dev->max_mtu = bp->jumbo_max_len - ETH_HLEN - ETH_FCS_LEN;
 	else
 		dev->max_mtu = ETH_DATA_LEN;
 
-- 
2.30.2

Re: [PATCH net-next v2 1/1] net: macb: fix negative max_mtu size for sama5d3

[Claudiu.Beznea]

On 17.06.2022 10:16, Oleksij Rempel wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> JML register on probe will return zero . This register is configured
> later on macb_init_hw() which is called on open.
> Since we have zero, after header and FCS length subtraction we will get
> negative max_mtu size. This issue was affecting DSA drivers with MTU support
> (for example KSZ9477).
> 
> Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>

Reviewed-by: Claudiu Beznea <claudiu.beznea@microchip.com>


> ---
> changes v2:
> - properly describe fail reason
> - simplify max_mtu logic
> 
>  drivers/net/ethernet/cadence/macb_main.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/ethernet/cadence/macb_main.c b/drivers/net/ethernet/cadence/macb_main.c
> index d89098f4ede8..d0ea8dbfa213 100644
> --- a/drivers/net/ethernet/cadence/macb_main.c
> +++ b/drivers/net/ethernet/cadence/macb_main.c
> @@ -4913,8 +4913,8 @@ static int macb_probe(struct platform_device *pdev)
> 
>         /* MTU range: 68 - 1500 or 10240 */
>         dev->min_mtu = GEM_MTU_MIN_SIZE;
> -       if (bp->caps & MACB_CAPS_JUMBO)
> -               dev->max_mtu = gem_readl(bp, JML) - ETH_HLEN - ETH_FCS_LEN;
> +       if ((bp->caps & MACB_CAPS_JUMBO) && bp->jumbo_max_len)
> +               dev->max_mtu = bp->jumbo_max_len - ETH_HLEN - ETH_FCS_LEN;
>         else
>                 dev->max_mtu = ETH_DATA_LEN;
> 
> --
> 2.30.2
> 

Re: [PATCH net-next v2 1/1] net: macb: fix negative max_mtu size for sama5d3

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (master)
by David S. Miller <davem@davemloft.net>:

On Fri, 17 Jun 2022 09:16:07 +0200 you wrote:
> JML register on probe will return zero . This register is configured
> later on macb_init_hw() which is called on open.
> Since we have zero, after header and FCS length subtraction we will get
> negative max_mtu size. This issue was affecting DSA drivers with MTU support
> (for example KSZ9477).
> 
> Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
> 
> [...]

Here is the summary with links:
  - [net-next,v2,1/1] net: macb: fix negative max_mtu size for sama5d3
    https://git.kernel.org/netdev/net-next/c/46e31db55da8

You are awesome, thank you!
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