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

["Rhodes, David" <drhodes@opensource.cirrus.com>]

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@cirrus.com> for more information on the ASoC driver for CS35L41.
> Please also cc patches@opensource.cirrus.com.
> 
> 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@collabora.com>

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