netdev - Re: [PATCH] net: mvpp2: add delay at the end of .mac

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Date:   Thu, 28 Apr 2022 10:59:59 +0200
From:   Marcin Wojtas <mw@...ihalf.com>
To:     Baruch Siach <baruch@...s.co.il>
Cc:     Russell King <linux@...linux.org.uk>,
        netdev <netdev@...r.kernel.org>,
        Baruch Siach <baruch.siach@...lu.com>
Subject: Re: [PATCH] net: mvpp2: add delay at the end of .mac_prepare

Hi Baruch,

śr., 27 kwi 2022 o 17:05 Baruch Siach <baruch@...s.co.il> napisał(a):
>
> From: Baruch Siach <baruch.siach@...lu.com>
>
> Without this delay PHY mode switch from XLG to SGMII fails in a weird
> way. Rx side works. However, Tx appears to work as far as the MAC is
> concerned, but packets don't show up on the wire.
>
> Tested with Marvell 10G 88X3310 PHY.
>
> Signed-off-by: Baruch Siach <baruch.siach@...lu.com>
> ---
>
> Not sure this is the right fix. Let me know if you have any better
> suggestion for me to test.
>
> The same issue and fix reproduce with both v5.18-rc4 and v5.10.110.
> ---
>  drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> index 1a835b48791b..8823efe396b1 100644
> --- a/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> +++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2_main.c
> @@ -6432,6 +6432,8 @@ static int mvpp2_mac_prepare(struct phylink_config *config, unsigned int mode,
>                 }
>         }
>
> +       mdelay(10);
> +
>         return 0;
>  }
>

Thank you for the patch and debug effort, however at first glance it
seems that adding delay may be a work-around and cover an actual root
cause (maybe Russell will have more input here).

Can you share exact reproduction steps?

Best regards,
Marcin