Re: [PATCH] ASoC: max98373: Mark cache dirty before entering sleep

[Pierre-Louis Bossart]

On 9/24/21 5:13 PM, Ryan Lee wrote:
> Amp lose its register values in case amp power loss or
> 'ForceReset' over Soundwire SCP_ctrl register(0x0044) or
> HW_RESET pin control during the audio suspend and resume.
> Mark cache dirty before audio suspension to restore
> existing values when audio resume.
> 
> Signed-off-by: Ryan Lee <ryans.lee@xxxxxxxxxxxxxxxxxxx>
> ---
>  sound/soc/codecs/max98373-sdw.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/sound/soc/codecs/max98373-sdw.c b/sound/soc/codecs/max98373-sdw.c
> index dc520effc61c..a7e4a6e880b0 100644
> --- a/sound/soc/codecs/max98373-sdw.c
> +++ b/sound/soc/codecs/max98373-sdw.c
> @@ -259,6 +259,7 @@ static __maybe_unused int max98373_suspend(struct device *dev)
>  		regmap_read(max98373->regmap, max98373->cache[i].reg, &max98373->cache[i].val);
>  
>  	regcache_cache_only(max98373->regmap, true);
> +	regcache_mark_dirty(max98373->regmap);

We already do the following sequence in max98373_io_init() when the
amplifier re-attaches:

	if (max98373->first_hw_init) {
		regcache_cache_bypass(max98373->regmap, false);
		regcache_mark_dirty(max98373->regmap);
	}

I don't see what marking the cache as dirty on suspend might do, we will
do a sync only in the resume step.

IIRC this is a patch that we've seen before and removed since it wasn't
aligned with any other codec driver.

Does this actually improve anything?