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authorClemens Ladisch <clemens@ladisch.de>2005-08-12 15:19:39 +0200
committerJaroslav Kysela <perex@suse.cz>2005-08-30 08:45:16 +0200
commita93bf99077886d209f8e72bc134e1ceb36e76aa2 (patch)
treea26ba330656f9d0aa693dabea5c585e266a90555 /sound
parent71d848ca00a16179b17e58e5f51c2d9a6c4f97a2 (diff)
[ALSA] usb-audio: schedule high speed URBs with 1 ms alignment
USB generic driver The EHCI driver doesn't interrupt more than once per millisecond, and organizes all iso transfers with frame-sized ITDs, so we can (try to) be more efficient by aligning all URBs on frame boundaries. Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
Diffstat (limited to 'sound')
-rw-r--r--sound/usb/usbaudio.c20
1 files changed, 14 insertions, 6 deletions
diff --git a/sound/usb/usbaudio.c b/sound/usb/usbaudio.c
index 49075f06f84..a62d1313da1 100644
--- a/sound/usb/usbaudio.c
+++ b/sound/usb/usbaudio.c
@@ -893,7 +893,7 @@ static int init_substream_urbs(snd_usb_substream_t *subs, unsigned int period_by
{
unsigned int maxsize, n, i;
int is_playback = subs->direction == SNDRV_PCM_STREAM_PLAYBACK;
- unsigned int npacks[MAX_URBS], urb_packs, total_packs;
+ unsigned int npacks[MAX_URBS], urb_packs, total_packs, packs_per_ms;
/* calculate the frequency in 16.16 format */
if (snd_usb_get_speed(subs->dev) == USB_SPEED_FULL)
@@ -920,14 +920,18 @@ static int init_substream_urbs(snd_usb_substream_t *subs, unsigned int period_by
else
subs->curpacksize = maxsize;
+ if (snd_usb_get_speed(subs->dev) == USB_SPEED_HIGH)
+ packs_per_ms = 8 >> subs->datainterval;
+ else
+ packs_per_ms = 1;
+
if (is_playback) {
urb_packs = nrpacks;
urb_packs = max(urb_packs, (unsigned int)MIN_PACKS_URB);
urb_packs = min(urb_packs, (unsigned int)MAX_PACKS);
} else
urb_packs = 1;
- if (snd_usb_get_speed(subs->dev) == USB_SPEED_HIGH)
- urb_packs = (urb_packs * 8) >> subs->datainterval;
+ urb_packs *= packs_per_ms;
/* allocate a temporary buffer for playback */
if (is_playback) {
@@ -949,8 +953,12 @@ static int init_substream_urbs(snd_usb_substream_t *subs, unsigned int period_by
minsize -= minsize >> 2;
minsize = max(minsize, 1u);
total_packs = (period_bytes + minsize - 1) / minsize;
- if (total_packs < 2 * MIN_PACKS_URB)
- total_packs = 2 * MIN_PACKS_URB;
+ /* round up to multiple of packs_per_ms */
+ total_packs = (total_packs + packs_per_ms - 1)
+ & ~(packs_per_ms - 1);
+ /* we need at least two URBs for queueing */
+ if (total_packs < 2 * MIN_PACKS_URB * packs_per_ms)
+ total_packs = 2 * MIN_PACKS_URB * packs_per_ms;
} else {
total_packs = MAX_URBS * urb_packs;
}
@@ -972,7 +980,7 @@ static int init_substream_urbs(snd_usb_substream_t *subs, unsigned int period_by
subs->nurbs = 2;
npacks[0] = (total_packs + 1) / 2;
npacks[1] = total_packs - npacks[0];
- } else if (npacks[subs->nurbs-1] < MIN_PACKS_URB) {
+ } 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 */