linux-kernel - Re: [PATCH] tty: max310x: work around regmap->regcache data corruption

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Message-ID: <CAHp75Vc4tB_CuT-e+gofanWK=mss-k_A-mqPo-8+Rv-aQ8tu_w@mail.gmail.com>
Date:   Fri, 1 Dec 2023 19:02:32 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Mark Brown <broonie@...nel.org>
Cc:     Jan Kundrát <jan.kundrat@...net.cz>,
        Cosmin Tanislav <cosmin.tanislav@...log.com>,
        linux-serial@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tty: max310x: work around regmap->regcache data corruption

On Fri, Dec 1, 2023 at 6:21 PM Mark Brown <broonie@...nel.org> wrote:
> On Fri, Dec 01, 2023 at 03:51:51PM +0100, Jan Kundrát wrote:
>
> > The TL;DR summary is that the regmap_noinc_write spills over the data
> > that are correctly written to the HW also to the following registers in
> > the regcache. As a result, regcache then contains user-controlled
> > garbage which will be used later for bit updates on unrelated registers.
>
> > I was investigating a regression that happened somewhere between 5.12.4
> > (plus 14 of our patches) and v6.5.9 (plus 7 of our patches). Our
>
> Can you reproduce this with current kernels?  That's not even an up to
> date v6.5 - we're up to v6.5.13 now from the looks of things including
> one upstream fix that looks potentially relevant.

Indeed, the 984a4afdc87a ("regmap: prevent noinc writes from
clobbering cache") seems quite relevant.

-- 
With Best Regards,
Andy Shevchenko