netdev - Re: [PATCH 0/9] renesas: Add compatible properties to Ethernet PHY nodes

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Message-ID: <CAMuHMdU6Mrfina3+2iW+RKaujk57JSRtmixRPn1b0d2w5dZ3eA@mail.gmail.com>
Date:   Thu, 23 Sep 2021 13:00:11 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>
Cc:     Biju Das <biju.das.jz@...renesas.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Adam Ford <aford173@...il.com>,
        Grygorii Strashko <grygorii.strashko@...com>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        netdev <netdev@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Geert Uytterhoeven <geert+renesas@...der.be>
Subject: Re: [PATCH 0/9] renesas: Add compatible properties to Ethernet PHY nodes

On Thu, Sep 9, 2021 at 10:49 AM Geert Uytterhoeven
<geert+renesas@...der.be> wrote:
> If an Ethernet PHY reset is asserted when the Ethernet driver is
> initialized, the PHY cannot be probed:
>
>     mdio_bus ee700000.ethernet-ffffffff: MDIO device at address 1 is missing
>
> This happens because the Linux PHY subsystem tries to read the PHY
> Identifier registers before handling PHY reset.  Hence if the PHY reset
> was asserted before, identification fails.
>
> An easy way to reproduce this issue is by using kexec to launch a new
> kernel (the PHY reset will be asserted before starting the new kernel),
> or by unbinding and rebinding the Ethernet driver (the PHY reset will be
> asserted during unbind), e.g. on koelsch:
>
>     echo ee700000.ethernet > /sys/bus/platform/drivers/sh-eth/unbind
>     $ echo ee700000.ethernet > /sys/bus/platform/drivers/sh-eth/bind
>
> The recommended approach[1][2] seems to be working around this issue by
> adding compatible values to all ethernet-phy nodes, so Linux can
> identify the PHY at any time, without reading the PHY ID from the
> device, and regardless of the state of the PHY reset line.
>
> Hence this patch series adds such compatible values to all Ethernet PHY
> subnodes representing PHYs on all boards with Renesas ARM and ARM64
> SoCs.  For easier review, I have split the series in one patch per PHY
> model.
>
> On most boards, I could verify the actual PHY ID at runtime[3], on other
> boards I had to resort to schematics.
>
> Kexec and Ethernet driver rebind have been tested on Koelsch and
> Salvator-XS.
>
> I plan to queue these in renesas-devel for v5.16.
>
> Thanks for your comments!

I'd be very grateful for comments (e.g. Acked-by) from the Ethernet
PHY people.
Thanks again!

> [1] "Re: [PATCH] RFC: net: phy: of phys probe/reset issue"
>     https://lore.kernel.org/r/ade12434-adf2-6ea7-24ce-ce45ad2e1b5e@gmail.com/
> [2] "PHY reset may still be asserted during MDIO probe"
>     https://lore.kernel.org/r/CAMuHMdXno2OUHqsAfO0z43JmGkFehD+FJ2dEjEsr_P53oAAPxA@mail.gmail.com
> [3] The easiest way to obtain the PHY ID is by adding a debug print to
>     drivers/net/phy/phy_device.c:get_phy_c22_id(), _before_ applying
>     this patch.
>
> Geert Uytterhoeven (9):
>   ARM: dts: renesas: Add compatible properties to KSZ8041 Ethernet PHYs
>   ARM: dts: renesas: Add compatible properties to KSZ8081 Ethernet PHYs
>   ARM: dts: renesas: Add compatible properties to KSZ9031 Ethernet PHYs
>   iARM: dts: renesas: Add compatible properties to LAN8710A Ethernet
>     PHYs
>   ARM: dts: renesas: Add compatible properties to RTL8201FL Ethernet
>     PHYs
>   ARM: dts: renesas: Add compatible properties to uPD6061x Ethernet PHYs
>   arm64: dts: renesas: Add compatible properties to AR8031 Ethernet PHYs
>   arm64: dts: renesas: Add compatible properties to KSZ9031 Ethernet
>     PHYs
>   arm64: dts: renesas: Add compatible properties to RTL8211E Ethernet
>     PHYs

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds