[PATCH 2/2] ALSA: usb-audio: Check connector value on resume

[Takashi Iwai]

On Wed, 24 Mar 2021 18:14:08 +0100,
Kai-Heng Feng wrote:
> 
> Rear Mic on Lenovo P620 cannot record after S3, despite that there's no
> error and the other two functions of the USB audio, Line In and Line
> Out, work just fine.
> 
> The mic starts to work again after running userspace app like "alsactl
> store". Following the lead, the evidence shows that as soon as connector
> status is queried, the mic can work again.
> 
> So also check connector value on resume to "wake up" the USB audio to
> make it functional.
> 
> This can be device specific, however I think this generic approach may
> benefit more than one device.
> 
> Signed-off-by: Kai-Heng Feng <kai.heng.feng at canonical.com>

Just to be sure: this workaround is always needed no matter whether
reset_resume is set or not?  If so, it's better to change the resume
callback to take reset_resume argument and call it always.  The
resume_connector() can be folded into there.


thanks,

Takashi

> ---
>  sound/usb/mixer.c | 18 ++++++++++++++++++
>  sound/usb/mixer.h |  1 +
>  2 files changed, 19 insertions(+)
> 
> diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
> index 98f5417a70e4..6a553d891b0f 100644
> --- a/sound/usb/mixer.c
> +++ b/sound/usb/mixer.c
> @@ -3631,11 +3631,28 @@ static int restore_mixer_value(struct usb_mixer_elem_list *list)
>  	return 0;
>  }
>  
> +static int resume_connector(struct usb_mixer_elem_list *list)
> +{
> +	struct usb_mixer_elem_info *cval = mixer_elem_list_to_info(list);
> +
> +	if (cval->val_type != USB_MIXER_BOOLEAN || cval->channels != 1)
> +		return 0;
> +
> +	return get_connector_value(cval, NULL, NULL);
> +}
> +
>  int snd_usb_mixer_resume(struct usb_mixer_interface *mixer, bool reset_resume)
>  {
>  	struct usb_mixer_elem_list *list;
>  	int id, err;
>  
> +	for (id = 0; id < MAX_ID_ELEMS; id++) {
> +		for_each_mixer_elem(list, mixer, id) {
> +			if (list->resume_connector)
> +				list->resume_connector(list);
> +		}
> +	}
> +
>  	if (reset_resume) {
>  		/* restore cached mixer values */
>  		for (id = 0; id < MAX_ID_ELEMS; id++) {
> @@ -3664,5 +3681,6 @@ void snd_usb_mixer_elem_init_std(struct usb_mixer_elem_list *list,
>  	list->dump = snd_usb_mixer_dump_cval;
>  #ifdef CONFIG_PM
>  	list->resume = restore_mixer_value;
> +	list->resume_connector = resume_connector;
>  #endif
>  }
> diff --git a/sound/usb/mixer.h b/sound/usb/mixer.h
> index c29e27ac43a7..843ccff0eea3 100644
> --- a/sound/usb/mixer.h
> +++ b/sound/usb/mixer.h
> @@ -69,6 +69,7 @@ struct usb_mixer_elem_list {
>  	bool is_std_info;
>  	usb_mixer_elem_dump_func_t dump;
>  	usb_mixer_elem_resume_func_t resume;
> +	usb_mixer_elem_resume_func_t resume_connector;
>  };
>  
>  /* iterate over mixer element list of the given unit id */
> -- 
> 2.30.2
>