A portion of USB Headsets loses previous sound volume setting after a suspend resume

[Takashi Iwai]

On Thu, 09 Sep 2021 12:21:46 +0200,
En-Shuo Hsu wrote:
> 
> Hi 
> 
> We recently found that some USB headsets may fall back to their full volume
> after a suspend and resume. We think the issue is caused by the logic of 
> mixer_ctl_feature_put in sound/usb/mixer.c:
> 
> err = snd_usb_get_cur_mix_value(cval, c + 1, cnt, &oval);
> if (err < 0)
>   return filter_error(cval, err);
>   val = ucontrol->value.integer.value[cnt];
>   val = get_abs_value(cval, val);
> if (oval != val) {
>   snd_usb_set_cur_mix_value(cval, c + 1, cnt, val);
>   changed = 1;
> }
> 
> The existing codes get the existing mixer control value and ignore the set if
> the val doesn't change. However, in the suspend and resume case, the USB
> headset's control value is actually changed.
> 
> Removing the cache logic is a potential fix, but a better solution may be to
> properly handle the suspend resume scenario in snd_usb_get_cur_mix_value. We
> may need to mark the cache in usb_mixer_elem_info to be dirty.
> 
> The issue is verified to be reproduced with Dell WH3022 and Logitech USB
> Headset H340 by:
> 1. Boot to OS.
> 2. Plug in the headset and check sound output.
> 3. Play an audio/video and keep with low volume.
> 4. Suspend.
> 5. Resume.
> 6. When audio/video is played, the headset's sound output can't keep the
> original volume. --> issue "
> 
> Would like to know your thoughts on this issue.

USB-audio driver has an assumption that the normal resume code
presumes the configuration while reset_resume needs the full
initialization, but this looks too naive, then.

Could you check the following works?


Takashi

--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -1080,7 +1080,7 @@ static int __usb_audio_resume(struct usb_interface *intf, bool reset_resume)
 	 * we just notify and restart the mixers
 	 */
 	list_for_each_entry(mixer, &chip->mixer_list, list) {
-		err = snd_usb_mixer_resume(mixer, reset_resume);
+		err = snd_usb_mixer_resume(mixer, true /*reset_resume*/);
 		if (err < 0)
 			goto err_out;
 	}