linux-kernel - Re: [PATCH net-next 0/2] net: dsa: realtek: fix PHY register read corruption

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Date:   Wed, 16 Feb 2022 14:57:11 -0300
From:   Luiz Angelo Daros de Luca <luizluca@...il.com>
To:     Alvin Šipraga <alvin@...s.dk>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Michael Rasmussen <mir@...g-olufsen.dk>,
        Alvin Šipraga <alsi@...g-olufsen.dk>,
        Arınç ÜNAL <arinc.unal@...nc9.com>,
        "open list:NETWORKING DRIVERS" <netdev@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next 0/2] net: dsa: realtek: fix PHY register read corruption

> These two patches fix the issue reported by Arınç where PHY register
> reads sometimes return garbage data.
>
> MAINTAINERS: Please can you help me with the targetting of these two
> patches? This bug is present ca. 5.16, when the SMI version of the
> rtl8365mb driver was introduced. But now in net-next we have the MDIO
> interface from Luiz, where the issue is also present. I am sending what
> I think is an ideal patch series, but should I split it up and send the
> SMI-related changes to net and the MDIO changes to net-next? If so, how
> would I go about splitting it while preventing merge conflicts and build
> errors?
>
> For now I am sending it to net-next so that the whole thing can be
> reviewed. If it's applied, I would gladly backport the fix to the stable
> tree for 5.16, but I am still confused about what to do for 5.17.
>
> Thanks for your help.
>
>
> Alvin Šipraga (2):
>   net: dsa: realtek: allow subdrivers to externally lock regmap
>   net: dsa: realtek: rtl8365mb: serialize indirect PHY register access
>
>  drivers/net/dsa/realtek/realtek-mdio.c | 46 +++++++++++++++++++++-
>  drivers/net/dsa/realtek/realtek-smi.c  | 48 +++++++++++++++++++++--
>  drivers/net/dsa/realtek/realtek.h      |  2 +
>  drivers/net/dsa/realtek/rtl8365mb.c    | 54 ++++++++++++++++----------
>  4 files changed, 124 insertions(+), 26 deletions(-)
>
> --
> 2.35.0
>

Thanks for the fix, Alvin.

I still feel like we are trying to go around a regmap limitation
instead of fixing it there. If we control regmap lock (we can define a
custom lock/unlock) and create new regmap_{read,write}_nolock
variants, we'll just need to lock the regmap, do whatever you need,
and unlock it.

BTW, I believe that, for realtek-mdio, a regmap custom lock mechanism
could simply use mdio lock while realtek-smi already has priv->lock.

Regards,