netdev - Re: [PATCH] net: ethernet: fec: Clear stale flag in IEVENT register before MII transfers

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Message-ID: <dbf9184d-adb2-6377-414b-0593ecb89149@pengutronix.de>
Date:   Fri, 11 Dec 2020 16:19:48 +0100
From:   Marian Cichy <mci@...gutronix.de>
To:     Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
        Andrew Lunn <andrew@...n.ch>
Cc:     netdev@...r.kernel.org, Fugang Duan <fugang.duan@....com>,
        "David S. Miller" <davem@...emloft.net>, kernel@...gutronix.de
Subject: Re: [PATCH] net: ethernet: fec: Clear stale flag in IEVENT register
 before MII transfers



On 12/9/20 5:51 PM, Uwe Kleine-König wrote:
> Hi Andrew,
>
> On Wed, Dec 09, 2020 at 03:44:13PM +0100, Andrew Lunn wrote:
>> On Wed, Dec 09, 2020 at 11:29:59AM +0100, Uwe Kleine-König wrote:
>> Do you have
>>
>> ommit 1e6114f51f9d4090390fcec2f5d67d8cc8dc4bfc
>> Author: Greg Ungerer <gerg@...ux-m68k.org>
>> Date:   Wed Oct 28 15:22:32 2020 +1000
>>
>>      net: fec: fix MDIO probing for some FEC hardware blocks
>>      
>>      Some (apparently older) versions of the FEC hardware block do not like
>>      the MMFR register being cleared to avoid generation of MII events at
>>      initialization time. The action of clearing this register results in no
>>      future MII events being generated at all on the problem block. This means
>>      the probing of the MDIO bus will find no PHYs.
>>      
>>      Create a quirk that can be checked at the FECs MII init time so that
>>      the right thing is done. The quirk is set as appropriate for the FEC
>>      hardware blocks that are known to need this.
>>
>> in your tree?
> Unless I did something wrong I also saw the failure with v5.10-rc$latest
> earlier today.
>
> ... some time later ...
>
> Argh, I checked my git reflog and the newest release I tested was
> 5.9-rc8.
>
> I wonder if my patch is a simpler and more straight forward fix for the
> problem however, but that might also be because I don't understand the
> comment touched by 1e6114f51f9d4090390fcec2f5d67d8cc8dc4bfc without
> checking the reference manual (which I didn't).
>
> @Marian: As it's you who has to work on this i.MX25 machine, can you
> maybe test if using a kernel > 5.10-rc3 (or cherry-picking
> 1e6114f51f9d4090390fcec2f5d67d8cc8dc4bfc) fixes the problem for you?

Tested it on 5.10-rc7 and the problem is fixed without your previous patch.

Best regards,
Marian

>
> Best regards
> Uwe
>