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From:   Andy Shevchenko <andy.shevchenko@gmail.com>
Date:   Fri, 1 Dec 2023 19:02:32 +0200
Message-ID: <CAHp75Vc4tB_CuT-e+gofanWK=mss-k_A-mqPo-8+Rv-aQ8tu_w@mail.gmail.com>
Subject: Re: [PATCH] tty: max310x: work around regmap->regcache data corruption
To:     Mark Brown <broonie@kernel.org>
Cc:     =?UTF-8?B?SmFuIEt1bmRyw6F0?= <jan.kundrat@cesnet.cz>,
        Cosmin Tanislav <cosmin.tanislav@analog.com>,
        linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org
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On Fri, Dec 1, 2023 at 6:21=E2=80=AFPM Mark Brown <broonie@kernel.org> wrot=
e:
> On Fri, Dec 01, 2023 at 03:51:51PM +0100, Jan Kundr=C3=A1t 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.

--=20
With Best Regards,
Andy Shevchenko