linux-kernel - Re: [PATCH v2] net: fec: manage corner deferred probe condition

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Message-ID: <CAJ=UCjXvcpV9gAfXv8An-pp=CK8J=sGE_adAoKeNFG1C-sMgJA@mail.gmail.com>
Date:   Sun, 15 Jan 2023 23:23:51 +0100
From:   Pierluigi Passaro <pierluigi.passaro@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Pierluigi Passaro <pierluigi.p@...iscite.com>, wei.fang@....com,
        shenwei.wang@....com, xiaoning.wang@....com, linux-imx@....com,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, eran.m@...iscite.com,
        nate.d@...iscite.com, francesco.f@...iscite.com
Subject: Re: [PATCH v2] net: fec: manage corner deferred probe condition

On Sun, Jan 15, 2023 at 10:56 PM Andrew Lunn <andrew@...n.ch> wrote:
> On Sun, Jan 15, 2023 at 10:38:04PM +0100, Pierluigi Passaro wrote:
> > For dual fec interfaces, external phys can only be configured by fec0.
> > When the function of_mdiobus_register return -EPROBE_DEFER, the driver
> > is lately called to manage fec1, which wrongly register its mii_bus as
> > fec0_mii_bus.
> > When fec0 retry the probe, the previous assignement prevent the MDIO bus
> > registration.
> > Use a static boolean to trace the orginal MDIO bus deferred probe and
> > prevent further registrations until the fec0 registration completed
> > succesfully.
>
> The real problem here seems to be that fep->dev_id is not
> deterministic. I think a better fix would be to make the mdio bus name
> deterministic. Use pdev->id instead of fep->dev_id + 1. That is what
> most mdiobus drivers use.
>
Actually, the sequence is deterministic, fec0 and then fec1,
but sometimes the GPIO of fec0 is not yet available.
The EPROBE_DEFER does not prevent the second instance from being probed.
This is the origin of the problem.
>
>         Andrew