[PATCH] ALSA: usb-audio: Explicitly set up the clock selector

[Geraldo Nascimento]

Thanks, Dr. Iwai!

I haven't tested the finalized patch yet, but I'll give it a shot on top of
5.12-rc7. Should be OK, nevertheless thorough testing is always a good idea.

Regards,
Geraldo

Em Ter, 13 de abr de 2021 05:41, Takashi Iwai <tiwai at suse.de> escreveu:

> In the current code, we have some assumption that the audio clock
> selector has been set up implicitly and don't want to touch it unless
> it's really needed for the fallback autoclock setup.  This works for
> most devices but some seem having a problem.  Partially this was
> covered for the devices with a single connector at the initialization
> phase (commit 086b957cc17f "ALSA: usb-audio: Skip the clock selector
> inquiry for single connections"), but also there are cases where the
> wrong clock set up is kept silently.  The latter seems to be the cause
> of the noises on Behringer devices.
>
> In this patch, we explicitly set up the audio clock selector whenever
> the appropriate node is found.
>
> Reported-by: Geraldo Nascimento <geraldogabriel at gmail.com>
> BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=199327
> Link:
> https://lore.kernel.org/r/CAEsQvcvF7LnO8PxyyCxuRCx=7jNeSCvFAd-+dE0g_rd1rOxxdw@mail.gmail.com
> Cc: <stable at vger.kernel.org>
> Signed-off-by: Takashi Iwai <tiwai at suse.de>
> ---
>  sound/usb/clock.c | 18 ++++++++++++++----
>  1 file changed, 14 insertions(+), 4 deletions(-)
>
> diff --git a/sound/usb/clock.c b/sound/usb/clock.c
> index a746802d0ac3..17bbde73d4d1 100644
> --- a/sound/usb/clock.c
> +++ b/sound/usb/clock.c
> @@ -296,7 +296,7 @@ static int __uac_clock_find_source(struct
> snd_usb_audio *chip,
>
>         selector = snd_usb_find_clock_selector(chip->ctrl_intf, entity_id);
>         if (selector) {
> -               int ret, i, cur;
> +               int ret, i, cur, err;
>
>                 if (selector->bNrInPins == 1) {
>                         ret = 1;
> @@ -324,13 +324,17 @@ static int __uac_clock_find_source(struct
> snd_usb_audio *chip,
>                 ret = __uac_clock_find_source(chip, fmt,
>                                               selector->baCSourceID[ret -
> 1],
>                                               visited, validate);
> +               if (ret > 0) {
> +                       err = uac_clock_selector_set_val(chip, entity_id,
> cur);
> +                       if (err < 0)
> +                               return err;
> +               }
> +
>                 if (!validate || ret > 0 || !chip->autoclock)
>                         return ret;
>
>                 /* The current clock source is invalid, try others. */
>                 for (i = 1; i <= selector->bNrInPins; i++) {
> -                       int err;
> -
>                         if (i == cur)
>                                 continue;
>
> @@ -396,7 +400,7 @@ static int __uac3_clock_find_source(struct
> snd_usb_audio *chip,
>
>         selector = snd_usb_find_clock_selector_v3(chip->ctrl_intf,
> entity_id);
>         if (selector) {
> -               int ret, i, cur;
> +               int ret, i, cur, err;
>
>                 /* the entity ID we are looking for is a selector.
>                  * find out what it currently selects */
> @@ -418,6 +422,12 @@ static int __uac3_clock_find_source(struct
> snd_usb_audio *chip,
>                 ret = __uac3_clock_find_source(chip, fmt,
>                                                selector->baCSourceID[ret -
> 1],
>                                                visited, validate);
> +               if (ret > 0) {
> +                       err = uac_clock_selector_set_val(chip, entity_id,
> cur);
> +                       if (err < 0)
> +                               return err;
> +               }
> +
>                 if (!validate || ret > 0 || !chip->autoclock)
>                         return ret;
>
> --
> 2.26.2
>
>