linux-kernel - Re: [PATCH] ASoC: tegra: Fix uninitialized flat cache warning in tegra210

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Message-ID: <3c8b0ff11a7b5bcc26c2e99b7369cb50d48621ec.camel@svanheule.net>
Date: Mon, 08 Dec 2025 21:57:01 +0100
From: Sander Vanheule <sander@...nheule.net>
To: "Sheetal ." <sheetal@...dia.com>, linux-sound@...r.kernel.org, Mark
 Brown	 <broonie@...nel.org>
Cc: Liam Girdwood <lgirdwood@...il.com>, Jaroslav Kysela <perex@...ex.cz>, 
 Takashi Iwai <tiwai@...e.com>, Thierry Reding <thierry.reding@...il.com>,
 Jonathan Hunter	 <jonathanh@...dia.com>, Charles Keepax
 <ckeepax@...nsource.cirrus.com>, 	linux-tegra@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ASoC: tegra: Fix uninitialized flat cache warning in
 tegra210_ahub

Hi,

On Mon, 2025-12-08 at 10:50 +0530, Sheetal . wrote:
> From: sheetal <sheetal@...dia.com>
> 
> The tegra210_ahub driver started triggering a warning after commit
> e062bdfdd6ad ("regmap: warn users about uninitialized flat cache"),
> which flags drivers using REGCACHE_FLAT without register defaults.
> Since the driver omits default definitions because its registers are
> zero initialized, the following warning is shown:
> 
>   WARNING KERN tegra210-ahub 2900800.ahub: using zero-initialized flat cache,
> this may cause unexpected behavior
> 
> Switch to REGCACHE_FLAT_S which is the recommended cache type for
> sparse register maps without defaults. This cache type initializes
> entries on-demand from hardware, eliminating the warning while using
> memory efficiently.
> 
> Fixes: e062bdfdd6ad ("regmap: warn users about uninitialized flat cache")

I disagree with this tag. The commit is working as intended by giving a warning.

This device's reset state happens to match the zero-initialization of the flat
cache, so there were no issues here. An earlier version of this sparse flat
cache indicated a potential problem with another driver, so there are likely
drivers out there that do need fixing:

https://lore.kernel.org/all/a2f7e2c3-f072-40f7-a865-5693b82b636e@sirena.org.uk/


Regardless, this patch could still be material for 6.19 to avoid unneeded
warnings, but that's up to Mark.

Best,
Sander