[ALSA] usb-audio: optimize handling of capture URBs
USB generic driver
When preparing capture URBs, we don't need to stop when we cross a
period boundary because we now never handle more than one millisecond of
data per URB anyway.
When handling captured data, use an extra flag to call
snd_pcm_period_elapsed() no more than once. This allows us to move the
period boundary checking code before the copying of the data which
avoids a second locking of the substream's lock.
Signed-off-by: Clemens Ladisch <clemens@ladisch.de>
diff --git a/sound/usb/usbaudio.c b/sound/usb/usbaudio.c
index a62d131..a703d96 100644
--- a/sound/usb/usbaudio.c
+++ b/sound/usb/usbaudio.c
@@ -311,27 +311,18 @@
struct urb *urb)
{
int i, offs;
- unsigned long flags;
snd_urb_ctx_t *ctx = (snd_urb_ctx_t *)urb->context;
offs = 0;
urb->dev = ctx->subs->dev; /* we need to set this at each time */
- urb->number_of_packets = 0;
- spin_lock_irqsave(&subs->lock, flags);
for (i = 0; i < ctx->packets; i++) {
urb->iso_frame_desc[i].offset = offs;
urb->iso_frame_desc[i].length = subs->curpacksize;
offs += subs->curpacksize;
- urb->number_of_packets++;
- subs->transfer_sched += subs->curframesize;
- if (subs->transfer_sched >= runtime->period_size) {
- subs->transfer_sched -= runtime->period_size;
- break;
- }
}
- spin_unlock_irqrestore(&subs->lock, flags);
urb->transfer_buffer = ctx->buf;
urb->transfer_buffer_length = offs;
+ urb->number_of_packets = ctx->packets;
#if 0 // for check
if (! urb->bandwidth) {
int bustime;
@@ -359,6 +350,7 @@
unsigned char *cp;
int i;
unsigned int stride, len, oldptr;
+ int period_elapsed = 0;
stride = runtime->frame_bits >> 3;
@@ -378,6 +370,10 @@
if (subs->hwptr_done >= runtime->buffer_size)
subs->hwptr_done -= runtime->buffer_size;
subs->transfer_done += len;
+ if (subs->transfer_done >= runtime->period_size) {
+ subs->transfer_done -= runtime->period_size;
+ period_elapsed = 1;
+ }
spin_unlock_irqrestore(&subs->lock, flags);
/* copy a data chunk */
if (oldptr + len > runtime->buffer_size) {
@@ -388,15 +384,9 @@
} else {
memcpy(runtime->dma_area + oldptr * stride, cp, len * stride);
}
- /* update the pointer, call callback if necessary */
- spin_lock_irqsave(&subs->lock, flags);
- if (subs->transfer_done >= runtime->period_size) {
- subs->transfer_done -= runtime->period_size;
- spin_unlock_irqrestore(&subs->lock, flags);
- snd_pcm_period_elapsed(subs->pcm_substream);
- } else
- spin_unlock_irqrestore(&subs->lock, flags);
}
+ if (period_elapsed)
+ snd_pcm_period_elapsed(subs->pcm_substream);
return 0;
}