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

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Date:   Mon, 18 Oct 2021 09:52:49 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Francesco Dolcini <francesco.dolcini@...adex.com>
Cc:     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>,
        christophe.leroy@...roup.eu, 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

On Mon, 18 Oct 2021 11:42:58 +0200 Francesco Dolcini wrote:
> 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.
> 
> [*] 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>

Is this the correct fixes tag?

Fixes: 1a5465f5d6a2 ("phy/micrel: Add suspend/resume support to Micrel PHYs")

Should we leave a comment in place of the callbacks referring 
to the errata?