Re: [PATCH v2] ASoC: codecs: lpass-wsa-macro: rewrite the interpolator volume after enabling clocks

[Johan Hovold <johan@kernel.org>]

On Tue, Sep 29, 2026 at 07:57:55AM -0400, Liviu Nicoara wrote:
> Commit 902f497a1ff5 ("ASoC: codecs: lpass-wsa-macro: remove useless
> gain read/write sequence") removed the read and write of the digital
> volume register in wsa_macro_enable_interpolator(), on the grounds that
> writing back the value just read does nothing. The comment above it,
> "apply gain after int clk is enabled", was left in place.
> 
> On the Dell XPS 13 9345 (X1E80100, four WSA8845 amplifiers on two WSA
> macros) the write does something: a volume change made while the path
> is idle does not take effect when playback starts. Lowering the digital
> volume from 81 to 63 with nothing playing, then playing a test tone,
> gave about the same level as before the change. With the rewrite
> restored, lowering it from 81 to 69 while idle played audibly quieter,
> and restoring 81 while idle brought the level back. Changes made during
> playback take effect with or without the rewrite.
> 
> The register already holds the new value when this happens. Without the
> rewrite, after an idle change from 69 to 81, playback stayed at the old
> level while the register, read from the hardware through /dev/mem, held
> the new one (0xfd). Writing that same value back through /dev/mem
> brought the level up at once.
> 
> This is the behaviour described in commit 46188db080bd ("ASoC: codecs:
> lpass-wsa-macro: fix compander volume hack"): "the volume registers
> still need to be written after enabling clocks in order for any prior
> updates to take effect." The value read comes from the register cache,
> so the write pushes the last requested volume to the hardware once its
> clock runs.
> 
> Restore the rewrite in the interpolator's POST_PMU event only. The mix
> path event removed later in the same series is not brought back.
> 
> Fixes: 902f497a1ff5 ("ASoC: codecs: lpass-wsa-macro: remove useless gain read/write sequence")
> Cc: stable@vger.kernel.org
> Assisted-by: Claude:claude-opus-5-5
> Signed-off-by: Liviu Nicoara <lnicoara@thinkoid.org>
> ---
> 
> Notes:
>     Changes in v2:
>     - Cc stable (Johan Hovold).
>     - Add the /dev/mem read and rewrite from the v1 review.
>     - Link to v1: https://lore.kernel.org/all/20260924125940.22665-1-lnicoara@thinkoid.org/
>     
>     Tested on v7.2.6 on the machine above, by listening. This function is
>     unchanged between v7.2 and for-next; the driver's clocks moved to the
>     PM clock framework in cd054a6e272c after v7.2, which was not tested
>     here. Build-tested on broonie/for-next (arm64 defconfig).

Thanks for the v2.

Reviewed-by: Johan Hovold <johan@kernel.org>

Johan