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

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Message-ID: <f66cf0a3-4d63-4548-8648-e93a1ef995e2@sirena.org.uk>
Date:   Fri, 1 Dec 2023 16:21:42 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Jan Kundrát <jan.kundrat@...net.cz>
Cc:     Cosmin Tanislav <cosmin.tanislav@...log.com>,
        linux-serial@...r.kernel.org,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tty: max310x: work around regmap->regcache data
 corruption

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.  The most direct thing
would be to write a kunit test demonstrating the issue with current
mainline.

If things are already fine with mainline then you'd need to talk to the
stable maintainers about what they've chosen to backport.  

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