linux-kernel - Re: [PATCH v1 0/3] Clean up and fix error handling in mdio_mux

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Message-ID: <7hfsvng2mj.fsf@baylibre.com>
Date:   Thu, 05 Aug 2021 11:36:36 -0700
From:   Kevin Hilman <khilman@...libre.com>
To:     Marc Zyngier <maz@...nel.org>,
        Saravana Kannan <saravanak@...gle.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Neil Armstrong <narmstrong@...libre.com>,
        kernel-team@...roid.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 0/3] Clean up and fix error handling in mdio_mux_init()

Marc Zyngier <maz@...nel.org> writes:

> Hi Saravana,
>
> On Wed, 04 Aug 2021 22:43:29 +0100,
> Saravana Kannan <saravanak@...gle.com> wrote:
>> 
>> This patch series was started due to -EPROBE_DEFER not being handled
>> correctly in mdio_mux_init() and causing issues [1]. While at it, I also
>> did some more error handling fixes and clean ups. The -EPROBE_DEFER fix is
>> the last patch.
>> 
>> Ideally, in the last patch we'd treat any error similar to -EPROBE_DEFER
>> but I'm not sure if it'll break any board/platforms where some child
>> mdiobus never successfully registers. If we treated all errors similar to
>> -EPROBE_DEFER, then none of the child mdiobus will work and that might be a
>> regression. If people are sure this is not a real case, then I can fix up
>> the last patch to always fail the entire mdio-mux init if any of the child
>> mdiobus registration fails.
>> 
>> Cc: Marc Zyngier <maz@...nel.org>
>> Cc: Neil Armstrong <narmstrong@...libre.com>
>> Cc: Kevin Hilman <khilman@...libre.com>
>> [1] - https://lore.kernel.org/lkml/CAGETcx95kHrv8wA-O+-JtfH7H9biJEGJtijuPVN0V5dUKUAB3A@mail.gmail.com/#t
>> 
>> Saravana Kannan (3):
>>   net: mdio-mux: Delete unnecessary devm_kfree
>>   net: mdio-mux: Don't ignore memory allocation errors
>>   net: mdio-mux: Handle -EPROBE_DEFER correctly
>> 
>>  drivers/net/mdio/mdio-mux.c | 37 ++++++++++++++++++++++++-------------
>>  1 file changed, 24 insertions(+), 13 deletions(-)
>
> Thanks for this. I've just gave it a go on my test platform, and this
> indeed addresses the issues I was seeing [1].
>
> Acked-by: Marc Zyngier <maz@...nel.org>
> Tested-by: Marc Zyngier <maz@...nel.org>

I wasn't seeing the same issues as Marc, but am heavily using everything
as modules on a few platforms using this code, and I'm not seeing any
regressions.

Thanks Saravana for finding the root cause here.

Acked-by: Kevin Hilman <khilman@...libre.com>
Signed-off-by: Kevin Hilman <khilman@...libre.com>

Kevin