ALSA: usb-audio: Reduce latency at playback start

[linux-2.6-microblaze.git] / sound / usb / pcm.c

diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index e26d373..c66831e 100644 (file)
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -613,11 +613,6 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
        subs->last_frame_number = 0;
        runtime->delay = 0;
 
-       /* for playback, submit the URBs now; otherwise, the first hwptr_done
-        * updates for all URBs would happen at the same time when starting */
-       if (subs->direction == SNDRV_PCM_STREAM_PLAYBACK)
-               ret = start_endpoints(subs);
-
  unlock:
        snd_usb_unlock_shutdown(chip);
        return ret;
@@ -1430,6 +1425,7 @@ static int snd_usb_substream_playback_trigger(struct snd_pcm_substream *substrea
                                              int cmd)
 {
        struct snd_usb_substream *subs = substream->runtime->private_data;
+       int err;
 
        switch (cmd) {
        case SNDRV_PCM_TRIGGER_START:
@@ -1440,6 +1436,14 @@ static int snd_usb_substream_playback_trigger(struct snd_pcm_substream *substrea
                                              prepare_playback_urb,
                                              retire_playback_urb,
                                              subs);
+               if (cmd == SNDRV_PCM_TRIGGER_START) {
+                       err = start_endpoints(subs);
+                       if (err < 0) {
+                               snd_usb_endpoint_set_callback(subs->data_endpoint,
+                                                             NULL, NULL, NULL);
+                               return err;
+                       }
+               }
                subs->running = 1;
                dev_dbg(&subs->dev->dev, "%d:%d Start Playback PCM\n",
                        subs->cur_audiofmt->iface,