ALSA: usb-audio: Save mixer status only once at suspend

The suspend callback of usb-audio driver may be called multiple times
per suspend when multiple USB interfaces are bound to a single sound
card instance.  In such a case, it's superfluous to save the mixer
values multiple times.  This patch fixes it by checking the counter.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 3 insertions, 2 deletions

diff --git a/sound/usb/card.c b/sound/usb/card.c
index 893d5a1afc3c..e769d3977716 100644
--- a/sound/usb/card.c
+++ b/sound/usb/card.c
@@ -695,8 +695,9 @@ static int usb_audio_suspend(struct usb_interface *intf, pm_message_t message)
                         chip->autosuspended = 1;
         }
 
-        list_for_each_entry(mixer, &chip->mixer_list, list)
-                snd_usb_mixer_suspend(mixer);
+        if (chip->num_suspended_intf == 1)
+                list_for_each_entry(mixer, &chip->mixer_list, list)
+                        snd_usb_mixer_suspend(mixer);
 
         return 0;
 }