1 files changed, 61 insertions, 45 deletions

diff --git a/sound/usb/endpoint.c b/sound/usb/endpoint.c
index 93e970f2b3c0..21dc6422d747 100644
--- a/sound/usb/endpoint.c
+++ b/sound/usb/endpoint.c
@@ -574,11 +574,14 @@ static int data_ep_set_params(struct snd_usb_endpoint *ep,
 			      snd_pcm_format_t pcm_format,
 			      unsigned int channels,
 			      unsigned int period_bytes,
+			      unsigned int frames_per_period,
+			      unsigned int periods_per_buffer,
 			      struct audioformat *fmt,
 			      struct snd_usb_endpoint *sync_ep)
 {
-	unsigned int maxsize, i, urb_packs, total_packs, packs_per_ms;
-	int is_playback = usb_pipeout(ep->pipe);
+	unsigned int maxsize, minsize, packs_per_ms, max_packs_per_urb;
+	unsigned int max_packs_per_period, urbs_per_period, urb_packs;
+	unsigned int max_urbs, i;
 	int frame_bits = snd_pcm_format_physical_width(pcm_format) * channels;
 
 	if (pcm_format == SNDRV_PCM_FORMAT_DSD_U16_LE && fmt->dsd_dop) {
@@ -611,58 +614,67 @@ static int data_ep_set_params(struct snd_usb_endpoint *ep,
 	else
 		ep->curpacksize = maxsize;
 
-	if (snd_usb_get_speed(ep->chip->dev) != USB_SPEED_FULL)
+	if (snd_usb_get_speed(ep->chip->dev) != USB_SPEED_FULL) {
 		packs_per_ms = 8 >> ep->datainterval;
-	else
-		packs_per_ms = 1;
-
-	if (is_playback && !snd_usb_endpoint_implicit_feedback_sink(ep)) {
-		urb_packs = max(ep->chip->nrpacks, 1);
-		urb_packs = min(urb_packs, (unsigned int) MAX_PACKS);
+		max_packs_per_urb = MAX_PACKS_HS;
 	} else {
-		urb_packs = 1;
+		packs_per_ms = 1;
+		max_packs_per_urb = MAX_PACKS;
 	}
+	if (sync_ep && !snd_usb_endpoint_implicit_feedback_sink(ep))
+		max_packs_per_urb = min(max_packs_per_urb,
+					1U << sync_ep->syncinterval);
+	max_packs_per_urb = max(1u, max_packs_per_urb >> ep->datainterval);
 
-	urb_packs *= packs_per_ms;
+	/*
+	 * Capture endpoints need to use small URBs because there's no way
+	 * to tell in advance where the next period will end, and we don't
+	 * want the next URB to complete much after the period ends.
+	 *
+	 * Playback endpoints with implicit sync much use the same parameters
+	 * as their corresponding capture endpoint.
+	 */
+	if (usb_pipein(ep->pipe) ||
+			snd_usb_endpoint_implicit_feedback_sink(ep)) {
 
-	if (sync_ep && !snd_usb_endpoint_implicit_feedback_sink(ep))
-		urb_packs = min(urb_packs, 1U << sync_ep->syncinterval);
+		/* make capture URBs <= 1 ms and smaller than a period */
+		urb_packs = min(max_packs_per_urb, packs_per_ms);
+		while (urb_packs > 1 && urb_packs * maxsize >= period_bytes)
+			urb_packs >>= 1;
+		ep->nurbs = MAX_URBS;
 
-	/* decide how many packets to be used */
-	if (is_playback && !snd_usb_endpoint_implicit_feedback_sink(ep)) {
-		unsigned int minsize, maxpacks;
+	/*
+	 * Playback endpoints without implicit sync are adjusted so that
+	 * a period fits as evenly as possible in the smallest number of
+	 * URBs.  The total number of URBs is adjusted to the size of the
+	 * ALSA buffer, subject to the MAX_URBS and MAX_QUEUE limits.
+	 */
+	} else {
 		/* determine how small a packet can be */
-		minsize = (ep->freqn >> (16 - ep->datainterval))
-			  * (frame_bits >> 3);
+		minsize = (ep->freqn >> (16 - ep->datainterval)) *
+				(frame_bits >> 3);
 		/* with sync from device, assume it can be 12% lower */
 		if (sync_ep)
 			minsize -= minsize >> 3;
 		minsize = max(minsize, 1u);
-		total_packs = (period_bytes + minsize - 1) / minsize;
-		/* we need at least two URBs for queueing */
-		if (total_packs < 2) {
-			total_packs = 2;
-		} else {
-			/* and we don't want too long a queue either */
-			maxpacks = max(MAX_QUEUE * packs_per_ms, urb_packs * 2);
-			total_packs = min(total_packs, maxpacks);
-		}
-	} else {
-		while (urb_packs > 1 && urb_packs * maxsize >= period_bytes)
-			urb_packs >>= 1;
-		total_packs = MAX_URBS * urb_packs;
-	}
 
-	ep->nurbs = (total_packs + urb_packs - 1) / urb_packs;
-	if (ep->nurbs > MAX_URBS) {
-		/* too much... */
-		ep->nurbs = MAX_URBS;
-		total_packs = MAX_URBS * urb_packs;
-	} else if (ep->nurbs < 2) {
-		/* too little - we need at least two packets
-		 * to ensure contiguous playback/capture
-		 */
-		ep->nurbs = 2;
+		/* how many packets will contain an entire ALSA period? */
+		max_packs_per_period = DIV_ROUND_UP(period_bytes, minsize);
+
+		/* how many URBs will contain a period? */
+		urbs_per_period = DIV_ROUND_UP(max_packs_per_period,
+				max_packs_per_urb);
+		/* how many packets are needed in each URB? */
+		urb_packs = DIV_ROUND_UP(max_packs_per_period, urbs_per_period);
+
+		/* limit the number of frames in a single URB */
+		ep->max_urb_frames = DIV_ROUND_UP(frames_per_period,
+					urbs_per_period);
+
+		/* try to use enough URBs to contain an entire ALSA buffer */
+		max_urbs = min((unsigned) MAX_URBS,
+				MAX_QUEUE * packs_per_ms / urb_packs);
+		ep->nurbs = min(max_urbs, urbs_per_period * periods_per_buffer);
 	}
 
 	/* allocate and initialize data urbs */
@@ -670,8 +682,7 @@ static int data_ep_set_params(struct snd_usb_endpoint *ep,
 		struct snd_urb_ctx *u = &ep->urb[i];
 		u->index = i;
 		u->ep = ep;
-		u->packets = (i + 1) * total_packs / ep->nurbs
-			- i * total_packs / ep->nurbs;
+		u->packets = urb_packs;
 		u->buffer_size = maxsize * u->packets;
 
 		if (fmt->fmt_type == UAC_FORMAT_TYPE_II)
@@ -748,6 +759,8 @@ out_of_memory:
  * @pcm_format: the audio fomat.
  * @channels: the number of audio channels.
  * @period_bytes: the number of bytes in one alsa period.
+ * @period_frames: the number of frames in one alsa period.
+ * @buffer_periods: the number of periods in one alsa buffer.
  * @rate: the frame rate.
  * @fmt: the USB audio format information
  * @sync_ep: the sync endpoint to use, if any
@@ -760,6 +773,8 @@ int snd_usb_endpoint_set_params(struct snd_usb_endpoint *ep,
 				snd_pcm_format_t pcm_format,
 				unsigned int channels,
 				unsigned int period_bytes,
+				unsigned int period_frames,
+				unsigned int buffer_periods,
 				unsigned int rate,
 				struct audioformat *fmt,
 				struct snd_usb_endpoint *sync_ep)
@@ -793,7 +808,8 @@ int snd_usb_endpoint_set_params(struct snd_usb_endpoint *ep,
 	switch (ep->type) {
 	case  SND_USB_ENDPOINT_TYPE_DATA:
 		err = data_ep_set_params(ep, pcm_format, channels,
-					 period_bytes, fmt, sync_ep);
+					 period_bytes, period_frames,
+					 buffer_periods, fmt, sync_ep);
 		break;
 	case  SND_USB_ENDPOINT_TYPE_SYNC:
 		err = sync_ep_set_params(ep, fmt);