Re: [PATCH] ASoC: cs35l41: Restore register state after system sleep

[Rhodes, David]

On 6/16/26 11:31 AM, Stefan Binding wrote:
> Hi,
>
> I have some concerns about this patch.
>
> This driver is used for more than just the Steam Deck, so we would need to ensure that this patch doesn't break those systems.
> There are some potential complexities around cs35l41 with respect to Boost and DSP enablement that need careful thought when supporting system sleep.
>
> The HDA equivalent driver for cs35l41 does have support for system sleep, but this driver works very differently.
>
> I recommend reaching out to David Rhodes <david.rhodes@xxxxxxxxxx> for more information on the ASoC driver for CS35L41.
> Please also cc patches@xxxxxxxxxxxxxxxxxxxxx.
>
> Thanks,
>
> Stefan
>
> On 15/06/2026 15:54, Nícolas F. R. A. Prado wrote:
> > Currently, on the Steam Deck LCD when the system goes into hibernation
> > and resumes back, the speakers are silent when playing with:
> >
> >    aplay -D plughw:acp5x,1 /usr/share/sounds/alsa/Front_Left.wav
> >
> > A crude workaround was to, after resuming the system, bypassing the
> > regmap cache on the cs35l41 devices, before playing:
> >
> >    echo 1 > /sys/kernel/debug/regmap/spi-VLV1776\:00/cache_bypass
> >    echo 1 > /sys/kernel/debug/regmap/spi-VLV1776\:01/cache_bypass
> >
> > That indicated that the hardware registers had gone out of sync with
> > the regmap cache due to the power down in system hibernation.
> >
> > Fix the issue by, before system sleep, marking the regcache as cache
> > only, and after system sleep, resetting the hardware and restoring the
> > hardware registers from the regcache.
> >
> > This gets the sound working on the Steam Deck LCD after resume from S4.
> >
> > While the issue was only observed on S4 on this platform, the callbacks
> > for suspend/resume are also set in the same way to account for platforms
> > that might power down the chip on S3 as well.
> >
> > Note that this change does not take care of restoring the DSP state,
> > since the affected platform does not use the DSP and it couldn't be
> > tested, so it is only shut down on resume so it can be reinitialized in
> > a future DSP preload event.
> >
> > Assisted-by: Copilot:claude-sonnet-4.6
> > Signed-off-by: Nícolas F. R. A. Prado <nfraprado@xxxxxxxxxxxxx>

Hi Nicholas,

I share Stefan's concerns about this patch affecting other devices. I 
also wonder if there is a less crude workaround for your system's behavior.

The existing driver uses runtime_suspend/runtime_resume to enter and 
exit a low power 'hibernation' mode 
(wm_adsp_hibernate/cs35l41_enter_hibernate). In this mode the part will 
lose some configuration so the regmap is put into cache_only for the 
duration of the sleep and synced when waking up.

Are you sure the device is not just missing a runtime_resume after the 
system is in S4? This whole sequence of sys operations should only be 
needed if the amp is completely losing power.

Thanks,
David