1 files changed, 58 insertions, 9 deletions

diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index a1298f379428..f782ce19bf5a 100644
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -212,7 +212,7 @@ int snd_usb_init_pitch(struct snd_usb_audio *chip, int iface,
 	}
 }
 
-static int start_endpoints(struct snd_usb_substream *subs)
+static int start_endpoints(struct snd_usb_substream *subs, int can_sleep)
 {
 	int err;
 
@@ -225,7 +225,7 @@ static int start_endpoints(struct snd_usb_substream *subs)
 		snd_printdd(KERN_DEBUG "Starting data EP @%p\n", ep);
 
 		ep->data_subs = subs;
-		err = snd_usb_endpoint_start(ep);
+		err = snd_usb_endpoint_start(ep, can_sleep);
 		if (err < 0) {
 			clear_bit(SUBSTREAM_FLAG_DATA_EP_STARTED, &subs->flags);
 			return err;
@@ -236,10 +236,25 @@ static int start_endpoints(struct snd_usb_substream *subs)
 	    !test_and_set_bit(SUBSTREAM_FLAG_SYNC_EP_STARTED, &subs->flags)) {
 		struct snd_usb_endpoint *ep = subs->sync_endpoint;
 
+		if (subs->data_endpoint->iface != subs->sync_endpoint->iface ||
+		    subs->data_endpoint->alt_idx != subs->sync_endpoint->alt_idx) {
+			err = usb_set_interface(subs->dev,
+						subs->sync_endpoint->iface,
+						subs->sync_endpoint->alt_idx);
+			if (err < 0) {
+				snd_printk(KERN_ERR
+					   "%d:%d:%d: cannot set interface (%d)\n",
+					   subs->dev->devnum,
+					   subs->sync_endpoint->iface,
+					   subs->sync_endpoint->alt_idx, err);
+				return -EIO;
+			}
+		}
+
 		snd_printdd(KERN_DEBUG "Starting sync EP @%p\n", ep);
 
 		ep->sync_slave = subs->data_endpoint;
-		err = snd_usb_endpoint_start(ep);
+		err = snd_usb_endpoint_start(ep, can_sleep);
 		if (err < 0) {
 			clear_bit(SUBSTREAM_FLAG_SYNC_EP_STARTED, &subs->flags);
 			return err;
@@ -547,7 +562,7 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
 	/* 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)
-		return start_endpoints(subs);
+		return start_endpoints(subs, 1);
 
 	return 0;
 }
@@ -1029,6 +1044,7 @@ static void prepare_playback_urb(struct snd_usb_substream *subs,
 				 struct urb *urb)
 {
 	struct snd_pcm_runtime *runtime = subs->pcm_substream->runtime;
+	struct snd_usb_endpoint *ep = subs->data_endpoint;
 	struct snd_urb_ctx *ctx = urb->context;
 	unsigned int counts, frames, bytes;
 	int i, stride, period_elapsed = 0;
@@ -1040,7 +1056,11 @@ static void prepare_playback_urb(struct snd_usb_substream *subs,
 	urb->number_of_packets = 0;
 	spin_lock_irqsave(&subs->lock, flags);
 	for (i = 0; i < ctx->packets; i++) {
-		counts = ctx->packet_size[i];
+		if (ctx->packet_size[i])
+			counts = ctx->packet_size[i];
+		else
+			counts = snd_usb_endpoint_next_packet_size(ep);
+
 		/* set up descriptor */
 		urb->iso_frame_desc[i].offset = frames * stride;
 		urb->iso_frame_desc[i].length = counts * stride;
@@ -1091,7 +1111,16 @@ static void prepare_playback_urb(struct snd_usb_substream *subs,
 	subs->hwptr_done += bytes;
 	if (subs->hwptr_done >= runtime->buffer_size * stride)
 		subs->hwptr_done -= runtime->buffer_size * stride;
+
+	/* update delay with exact number of samples queued */
+	runtime->delay = subs->last_delay;
 	runtime->delay += frames;
+	subs->last_delay = runtime->delay;
+
+	/* realign last_frame_number */
+	subs->last_frame_number = usb_get_current_frame_number(subs->dev);
+	subs->last_frame_number &= 0xFF; /* keep 8 LSBs */
+
 	spin_unlock_irqrestore(&subs->lock, flags);
 	urb->transfer_buffer_length = bytes;
 	if (period_elapsed)
@@ -1109,12 +1138,32 @@ static void retire_playback_urb(struct snd_usb_substream *subs,
 	struct snd_pcm_runtime *runtime = subs->pcm_substream->runtime;
 	int stride = runtime->frame_bits >> 3;
 	int processed = urb->transfer_buffer_length / stride;
+	int est_delay;
+
+	/* ignore the delay accounting when procssed=0 is given, i.e.
+	 * silent payloads are procssed before handling the actual data
+	 */
+	if (!processed)
+		return;
 
 	spin_lock_irqsave(&subs->lock, flags);
-	if (processed > runtime->delay)
-		runtime->delay = 0;
+	est_delay = snd_usb_pcm_delay(subs, runtime->rate);
+	/* update delay with exact number of samples played */
+	if (processed > subs->last_delay)
+		subs->last_delay = 0;
 	else
-		runtime->delay -= processed;
+		subs->last_delay -= processed;
+	runtime->delay = subs->last_delay;
+
+	/*
+	 * Report when delay estimate is off by more than 2ms.
+	 * The error should be lower than 2ms since the estimate relies
+	 * on two reads of a counter updated every ms.
+	 */
+	if (abs(est_delay - subs->last_delay) * 1000 > runtime->rate * 2)
+		snd_printk(KERN_DEBUG "delay: estimated %d, actual %d\n",
+			est_delay, subs->last_delay);
+
 	spin_unlock_irqrestore(&subs->lock, flags);
 }
 
@@ -1172,7 +1221,7 @@ static int snd_usb_substream_capture_trigger(struct snd_pcm_substream *substream
 
 	switch (cmd) {
 	case SNDRV_PCM_TRIGGER_START:
-		err = start_endpoints(subs);
+		err = start_endpoints(subs, 0);
 		if (err < 0)
 			return err;