linux-kernel - Re: [PATCH] regmap: Ensure range selector registers are updated after cache sync

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Message-ID: <66c2f5d4-23de-4faf-a816-919516927f94@sirena.org.uk>
Date:   Thu, 26 Oct 2023 17:22:11 +0100
From:   Mark Brown <broonie@...nel.org>
To:     Hector Martin <marcan@...can.st>, linux-kernel@...r.kernel.org
Cc:     stable@...r.kernel.org
Subject: Re: [PATCH] regmap: Ensure range selector registers are updated
 after cache sync

On Thu, Oct 26, 2023 at 04:49:19PM +0100, Mark Brown wrote:
> When we sync the register cache we do so with the cache bypassed in order
> to avoid overhead from writing the synced values back into the cache. If
> the regmap has ranges and the selector register for those ranges is in a
> register which is cached this has the unfortunate side effect of meaning
> that the physical and cached copies of the selector register can be out of
> sync after a cache sync. The cache will have whatever the selector was when
> the sync started and the hardware will have the selector for the register
> that was synced last.

Given the nearness to the release I've dropped this into my CI and am
intending to just apply it as soon as that's done in the hopes that it
hits tomorrow's -next and gets a bit more coverage, it would be great if
you could confirm if this fixes the systems where you saw the original
issue.

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