sound: usb-audio: do not make URBs longer than sync packet interval

Using more packets in one URB do avoid interrupts does not make sense
when we have a sync pipe whose packets generate interrupts more often.
Therefore, limit the URB size to the synchronization packet interval.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 2 insertions, 0 deletions

diff --git a/sound/usb/usbaudio.c b/sound/usb/usbaudio.c
index 44b9cdc8a83b..fa3f7a1dc5e1 100644
--- a/sound/usb/usbaudio.c
+++ b/sound/usb/usbaudio.c
@@ -1083,6 +1083,8 @@ static int init_substream_urbs(struct snd_usb_substream *subs, unsigned int peri
         } else
                 urb_packs = 1;
         urb_packs *= packs_per_ms;
+        if (subs->syncpipe)
+                urb_packs = min(urb_packs, 1 << subs->syncinterval);
 
         /* decide how many packets to be used */
         if (is_playback) {