Commit 160389c8 authored by Clemens Ladisch's avatar Clemens Ladisch Committed by Takashi Iwai
Browse files

sound: usb-audio: make URB sizes more equal 



Distribute the packets evenly among the URBs, instead of making all URBs
except the last one to have the maximum size.  This makes the timing of
pointer updates more regular and removes some special cases from the
code.

Signed-off-by: default avatarClemens Ladisch <clemens@ladisch.de>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent 4d788e04

sound/usb/usbaudio.c

+5 −24
Original line number Diff line number Diff line
@@ -1035,9 +1035,9 @@ static void release_substream_urbs(struct snd_usb_substream *subs, int force) 
static int init_substream_urbs(struct snd_usb_substream *subs, unsigned int period_bytes,

			       unsigned int rate, unsigned int frame_bits)

{

	unsigned int maxsize, n, i;

	unsigned int maxsize, i;

	int is_playback = subs->direction == SNDRV_PCM_STREAM_PLAYBACK;

	unsigned int npacks[MAX_URBS], urb_packs, total_packs, packs_per_ms;

	unsigned int urb_packs, total_packs, packs_per_ms;



	/* calculate the frequency in 16.16 format */

	if (snd_usb_get_speed(subs->dev) == USB_SPEED_FULL)
@@ -1109,31 +1109,11 @@ static int init_substream_urbs(struct snd_usb_substream *subs, unsigned int peri 
		/* too much... */

		subs->nurbs = MAX_URBS;

		total_packs = MAX_URBS * urb_packs;

	}

	n = total_packs;

	for (i = 0; i < subs->nurbs; i++) {

		npacks[i] = n > urb_packs ? urb_packs : n;

		n -= urb_packs;

	}

	if (subs->nurbs <= 1) {

	} else if (subs->nurbs < 2) {

		/* too little - we need at least two packets

		 * to ensure contiguous playback/capture

		 */

		subs->nurbs = 2;

		npacks[0] = (total_packs + 1) / 2;

		npacks[1] = total_packs - npacks[0];

	} else if (npacks[subs->nurbs-1] < MIN_PACKS_URB * packs_per_ms) {

		/* the last packet is too small.. */

		if (subs->nurbs > 2) {

			/* merge to the first one */

			npacks[0] += npacks[subs->nurbs - 1];

			subs->nurbs--;

		} else {

			/* divide to two */

			subs->nurbs = 2;

			npacks[0] = (total_packs + 1) / 2;

			npacks[1] = total_packs - npacks[0];

		}

	}



	/* allocate and initialize data urbs */
@@ -1141,7 +1121,8 @@ static int init_substream_urbs(struct snd_usb_substream *subs, unsigned int peri 
		struct snd_urb_ctx *u = &subs->dataurb[i];

		u->index = i;

		u->subs = subs;

		u->packets = npacks[i];

		u->packets = (i + 1) * total_packs / subs->nurbs

			- i * total_packs / subs->nurbs;

		u->buffer_size = maxsize * u->packets;

		if (subs->fmt_type == USB_FORMAT_TYPE_II)

			u->packets++; /* for transfer delimiter */

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