netdev - Re: What's the expected path to recover from a PHY

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Message-ID: <CAJ-Vmo=rgT1e3pPQHffjmRoRmHsQrmfQdSTRHqqnNGeLGRZZHw@mail.gmail.com>
Date:	Mon, 16 Nov 2015 12:05:41 -0800
From:	Adrian Chadd <adrian@...ebsd.org>
To:	Florian Fainelli <f.fainelli@...il.com>
Cc:	netdev@...r.kernel.org
Subject: Re: What's the expected path to recover from a PHY_HALTED transition?

On 16 November 2015 at 11:48, Florian Fainelli <f.fainelli@...il.com> wrote:
> On 16/11/15 11:29, Adrian Chadd wrote:
>> hi,
>>
>> I'm debugging an issue on the Broadcom parts (using unimac-mdio.c as
>> the mdio bus) where i occasionally see MDIO bus read failures, which
>> causes phy.c to transition the PHY to PHY_HALTED. It stays in this
>> state until the link is bounced.
>
> There is a known problem with some Broadcom PHYs where the first MDIO
> read may fail, and this can actually show up randomly in time, not just
> the first read and that caused the PHY library to enter PHY_HALTED.
> Which part are you seeing this? unimac-mdio.c has a reset hook just for
> that cases.

It's the broadcom BCM7444.

The failure is -EIO from the unimac-mdio read method, which only
happens when the hardware returns MDIO_READ_FAIL.

>> So, what's the expectation to handle this and recover from it? is
>> there some userland piece monitoring things that I'm missing?
>
> There is not much you can do typically, but ignore or retry the read, or
> workaround it if you can, like what bcm7xxx.c does.

What's the reset hack in bcm7xxx.c ? I don't see anything obvious.

(I'm currently stuck on 3.14.13-1.2 from broadcom's stb tree.)

Thanks,



-adrian
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