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

[Rhodes, David]

On 7/21/26 3:08 PM, Nícolas F. R. A. Prado wrote:

> Also, since on my system the DSP is not used, the early return in the
> runtime suspend/resume `if (!cs35l41->dsp.preloaded || !cs35l41-
> > dsp.cs_dsp.running)` means that the runtime suspend/resume callbacks
> are no-ops on my system.

The Steam Deck LCD should be using the DSP firmware. Valve distributed 
this initially but it was added to linux-firmware early last year.
See 'cirrus/cs35l41-dsp1-spk-prot-vlv1776.bin'.

> Nonetheless, I tried simply marking the regcache dirty and syncing it
> upon system resume, mimicking the runtime suspend/resume, as follows:

> Given that my patch that fully reinitializes the hardware works, while
> this doesn't, I'm inclined to believe that the chip loses power during
> S4 indeed, at which point just restoring the register state is no
> longer enough. But perhaps you could shed more light into this since
> you're much more familiar with this hardware than I am.
>
> Thanks,
> Nícolas

Thank you for looking into this. I agree with your conclusion that the 
chip is fully losing power. With that in mind, your implementation makes 
sense.

Given the above comments about disabling the DSP on your system, I have 
to ask: Are you working on a 'standard' Steam Deck, or have you made 
other changes to the power management that aren't present on a typical 
device? Has this always been an issue affecting the Steam Deck LCD?

The Steam Deck is the primary use for this ASoC driver. Valve is 
regularly updating the kernel in their OS releases, so I don't want to 
make any changes that affect the out-of-box behavior. Of course if you 
are in touch with Valve and submitting this on their behalf, no worries 
and I'd love to see an Ack from someone on their side.

Thanks,
David