linux-kernel - Re: [PATCH net-next] phy: micrel: ksz8041nl: do not use power down mode

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Date:   Mon, 18 Oct 2021 11:53:03 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Francesco Dolcini <francesco.dolcini@...adex.com>,
        f.fainelli@...il.com, Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Stefan Agner <stefan@...er.ch>,
        Marcel Ziswiler <marcel.ziswiler@...adex.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] phy: micrel: ksz8041nl: do not use power down
 mode



Le 18/10/2021 à 11:42, Francesco Dolcini a écrit :
> From: Stefan Agner <stefan@...er.ch>
> 
> Some Micrel KSZ8041NL PHY chips exhibit continous RX errors after using
> the power down mode bit (0.11). If the PHY is taken out of power down
> mode in a certain temperature range, the PHY enters a weird state which
> leads to continously reporting RX errors. In that state, the MAC is not
> able to receive or send any Ethernet frames and the activity LED is
> constantly blinking. Since Linux is using the suspend callback when the
> interface is taken down, ending up in that state can easily happen
> during a normal startup.
> 
> Micrel confirmed the issue in errata DS80000700A [*], caused by abnormal
> clock recovery when using power down mode. Even the latest revision (A4,
> Revision ID 0x1513) seems to suffer that problem, and according to the
> errata is not going to be fixed.
> 
> Remove the suspend/resume callback to avoid using the power down mode
> completely.

As far as I can see in the ERRATA, KSZ8041 RNLI also has the bug.
Shoudn't you also remove the suspend/resume on that one (which follows 
in ksphy_driver[])

Christophe

> 
> [*] https://ww1.microchip.com/downloads/en/DeviceDoc/80000700A.pdf
> 
> Signed-off-by: Stefan Agner <stefan@...er.ch>
> Acked-by: Marcel Ziswiler <marcel.ziswiler@...adex.com>
> Signed-off-by: Francesco Dolcini <francesco.dolcini@...adex.com>
> 
> ---
> There was a previous attempt to merge a similar patch, see
> https://lore.kernel.org/all/2ee9441d-1b3b-de6d-691d-b615c04c69d0@gmail.com/.
> ---
>   drivers/net/phy/micrel.c | 2 --
>   1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/net/phy/micrel.c b/drivers/net/phy/micrel.c
> index ff452669130a..1f28d5fae677 100644
> --- a/drivers/net/phy/micrel.c
> +++ b/drivers/net/phy/micrel.c
> @@ -1676,8 +1676,6 @@ static struct phy_driver ksphy_driver[] = {
>   	.get_sset_count = kszphy_get_sset_count,
>   	.get_strings	= kszphy_get_strings,
>   	.get_stats	= kszphy_get_stats,
> -	.suspend	= genphy_suspend,
> -	.resume		= genphy_resume,
>   }, {
>   	.phy_id		= PHY_ID_KSZ8041RNLI,
>   	.phy_id_mask	= MICREL_PHY_ID_MASK,
>