ALSA: usb-audio: Avoid killing in-flight URBs during draining

While draining a stream, ALSA PCM core stops the stream by issuing
snd_pcm_stop() after all data has been sent out.  And, at PCM trigger
stop, currently USB-audio driver kills the in-flight URBs explicitly,
then at sync-stop ops, sync with the finish of all remaining URBs.
This might result in a drop of the drained samples as most of
USB-audio devices / hosts allow relatively long in-flight samples (as
a sort of FIFO).

For avoiding the trimming, this patch changes the stream-stop behavior
during PCM draining state.  Under that condition, the pending URBs
won't be killed.  The leftover in-flight URBs are caught by the
sync-stop operation that shall be performed after the trigger-stop
operation.

Link: https://lore.kernel.org/r/20210929080844.11583-10-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

1 files changed, 8 insertions, 8 deletions

diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index d5a14e5b9ad3..f09c7380a923 100644
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -219,16 +219,16 @@ int snd_usb_init_pitch(struct snd_usb_audio *chip,
 	return 0;
 }
 
-static bool stop_endpoints(struct snd_usb_substream *subs)
+static bool stop_endpoints(struct snd_usb_substream *subs, bool keep_pending)
 {
 	bool stopped = 0;
 
 	if (test_and_clear_bit(SUBSTREAM_FLAG_SYNC_EP_STARTED, &subs->flags)) {
-		snd_usb_endpoint_stop(subs->sync_endpoint);
+		snd_usb_endpoint_stop(subs->sync_endpoint, keep_pending);
 		stopped = true;
 	}
 	if (test_and_clear_bit(SUBSTREAM_FLAG_DATA_EP_STARTED, &subs->flags)) {
-		snd_usb_endpoint_stop(subs->data_endpoint);
+		snd_usb_endpoint_stop(subs->data_endpoint, keep_pending);
 		stopped = true;
 	}
 	return stopped;
@@ -261,7 +261,7 @@ static int start_endpoints(struct snd_usb_substream *subs)
 	return 0;
 
  error:
-	stop_endpoints(subs);
+	stop_endpoints(subs, false);
 	return err;
 }
 
@@ -437,7 +437,7 @@ static int configure_endpoints(struct snd_usb_audio *chip,
 
 	if (subs->data_endpoint->need_setup) {
 		/* stop any running stream beforehand */
-		if (stop_endpoints(subs))
+		if (stop_endpoints(subs, false))
 			sync_pending_stops(subs);
 		err = snd_usb_endpoint_configure(chip, subs->data_endpoint);
 		if (err < 0)
@@ -572,7 +572,7 @@ static int snd_usb_hw_free(struct snd_pcm_substream *substream)
 	subs->cur_audiofmt = NULL;
 	mutex_unlock(&chip->mutex);
 	if (!snd_usb_lock_shutdown(chip)) {
-		if (stop_endpoints(subs))
+		if (stop_endpoints(subs, false))
 			sync_pending_stops(subs);
 		close_endpoints(chip, subs);
 		snd_usb_unlock_shutdown(chip);
@@ -1559,7 +1559,7 @@ static int snd_usb_substream_playback_trigger(struct snd_pcm_substream *substrea
 		return 0;
 	case SNDRV_PCM_TRIGGER_SUSPEND:
 	case SNDRV_PCM_TRIGGER_STOP:
-		stop_endpoints(subs);
+		stop_endpoints(subs, substream->runtime->status->state == SNDRV_PCM_STATE_DRAINING);
 		snd_usb_endpoint_set_callback(subs->data_endpoint,
 					      NULL, NULL, NULL);
 		subs->running = 0;
@@ -1607,7 +1607,7 @@ static int snd_usb_substream_capture_trigger(struct snd_pcm_substream *substream
 		return 0;
 	case SNDRV_PCM_TRIGGER_SUSPEND:
 	case SNDRV_PCM_TRIGGER_STOP:
-		stop_endpoints(subs);
+		stop_endpoints(subs, false);
 		fallthrough;
 	case SNDRV_PCM_TRIGGER_PAUSE_PUSH:
 		snd_usb_endpoint_set_callback(subs->data_endpoint,