linux-kernel - Re: [PATCH] of_mdio: Fix broken PHY IRQ in case of probe deferral

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Message-ID: <CAMuHMdV+jfh=EGt3SvjtrtVfWQ6P8ofp_JxeQZjRrSEfDWs5hA@mail.gmail.com>
Date:   Thu, 18 May 2017 22:36:13 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
        Sergei Shtylyov <sergei.shtylyov@...entembedded.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] of_mdio: Fix broken PHY IRQ in case of probe deferral

Hi Andrew,

On Thu, May 18, 2017 at 9:34 PM, Andrew Lunn <andrew@...n.ch> wrote:
>> > This most certainly works fine in the simple case where you have one PHY
>> > hanging off the MDIO bus, now what happens if you have several?
>> >
>> > Presumably, the first PHY that returns EPROBE_DEFER will make the entire
>> > bus registration return EPROB_DEFER as well, and so on, and so forth,
>> > but I am not sure if we will be properly unwinding the successful
>> > registration of PHYs that either don't have an interrupt, or did not
>> > return EPROBE_DEFER.
>> >
>> > It should be possible to mimic this behavior by using the fixed PHY, and
>> > possibly the dsa_loop.c driver which would create 4 ports, expecting 4
>> > fixed PHYs to be present.
>>
>> mdiobus_unregister(), called from of_mdiobus_register() on failure,
>> should do the unwinding, right?
>>
>> And when the driver is reprobed, all PHYs are reprobed, until they all
>> succeed.
>
> That is the theory. I looked at that while reviewing the patch. But
> this has probably not been tested in anger. It would be good to test
> this properly, with not just the first PHY returning -EPROBE_DEFER, to
> really test the unwind.

Unfortunately I don't have a board with multiple PHYs, so I cannot test
that case.

Does unbinding/rebinding a network driver with multiple PHYs currently
work? Or module unload/reload?

That should exercise a similar code path.

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