netdev - Re: FEC MDIO read timeout on linkup

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Date:   Fri, 22 Apr 2022 12:55:22 -0300
From:   Fabio Estevam <festevam@...il.com>
To:     Francesco Dolcini <francesco.dolcini@...adex.com>
Cc:     Joakim Zhang <qiangqing.zhang@....com>,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        netdev <netdev@...r.kernel.org>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        "David S. Miller" <davem@...emloft.net>,
        Tim Harvey <tharvey@...eworks.com>
Subject: Re: FEC MDIO read timeout on linkup

Hi Francesco,

On Fri, Apr 22, 2022 at 12:26 PM Francesco Dolcini
<francesco.dolcini@...adex.com> wrote:
>
> Hello all,
> I have been recently trying to debug an issue with FEC driver erroring
> a MDIO read timeout during linkup [0]. At the beginning I was working
> with an old 5.4 kernel, but today I tried with the current master
> (5.18.0-rc3-00080-gd569e86915b7) and the issue is just there.
>
> I'm also aware of the old discussions on the topic and I tried to
> increase the timeout without success (even if I'm not sure is relevant
> with the newer polling solution).
>
> The issue was reproduced on an apalis-imx6 that has a KSZ9131
> ethernet connected to the FEC MAC.
>
> No load on the machine, 4 cores just idling during my test.
>
> What I can see from the code is that the timeout is coming from
> net/phy/micrel.c:kszphy_handle_interrupt().

For debugging purposes, could you try not to describe the Ethernet PHY
irq pin inside imx6qdl-apalis.dtsi?

Looking at its pinctrl, I don't see it has pull-up enabled. Is there
an external pull-up
on the KSZ9131 pin?