Re: [PATCH] ALSA: ac97: drop stale CMI9738 PCM-volume quirk

[Takashi Iwai]

On Wed, 29 Apr 2026 14:05:31 +0200,
Cássio Gabriel wrote:
> 
> patch_cm9738() still carries an old comment claiming that CMI9738
> has no PCM volume although AC97_PCM reacts, and then forces
> AC97_HAS_NO_PCM_VOL.
> 
> The CMI9738 datasheet documents register 0x18 as "PCM Out Vol"
> with mute and left/right volume fields, so that old assumption is
> not justified.

Well, that's actually the part the FIXME points to.  Although the spec
shows the register is available and the chip reads out, the volume
didn't seem reacting properly on the real hardware, as far as I
remember correctly.

So, it's really doubtful whether it's safe to cut off this workaround
just by reading the data sheet.


thanks,

Takashi

> 
> Remove the comment together with the no-PCM-volume override and let
> the generic AC97 mixer code probe AC97_PCM normally. It already
> checks the mute bit and the register's volume resolution before
> exposing controls.
> 
> This change is intentionally limited to CMI9738.
> 
> Signed-off-by: Cássio Gabriel <cassiogabrielcontato@xxxxxxxxx>
> ---
>  sound/pci/ac97/ac97_patch.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/sound/pci/ac97/ac97_patch.c b/sound/pci/ac97/ac97_patch.c
> index 64cc39dd2008..5e9f70c47ed5 100644
> --- a/sound/pci/ac97/ac97_patch.c
> +++ b/sound/pci/ac97/ac97_patch.c
> @@ -3002,9 +3002,6 @@ static const struct snd_ac97_build_ops patch_cm9738_ops = {
>  static int patch_cm9738(struct snd_ac97 * ac97)
>  {
>  	ac97->build_ops = &patch_cm9738_ops;
> -	/* FIXME: can anyone confirm below? */
> -	/* CM9738 has no PCM volume although the register reacts */
> -	ac97->flags |= AC97_HAS_NO_PCM_VOL;
>  	snd_ac97_write_cache(ac97, AC97_PCM, 0x8000);
>  
>  	return 0;
> 
> ---
> base-commit: 116ed8afab5e3217561a6a8bc4ca1c3d5d97830c
> change-id: 20260429-ac97-cmi9738-pcm-volume-898bf48a92dd
> 
> Best regards,
> --  
> Cássio Gabriel <cassiogabrielcontato@xxxxxxxxx>
>