ALSA: usb-audio: support delay calculation on capture streams
Enable delay report on capture path. The delay is reset when an
URB is retired and increment at each call to .pointer based
on frame counter changes. The precision of the delay
information is limited to 1ms as in the playback case.
This reverts commit 3f94fad09538ec988919ec3f371841182df71d04.
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c
index c659310..3a38447 100644
--- a/sound/usb/pcm.c
+++ b/sound/usb/pcm.c
@@ -59,7 +59,12 @@
/* Approximation based on number of samples per USB frame (ms),
some truncation for 44.1 but the estimate is good enough */
- est_delay = subs->last_delay - (frame_diff * rate / 1000);
+ est_delay = frame_diff * rate / 1000;
+ if (subs->direction == SNDRV_PCM_STREAM_PLAYBACK)
+ est_delay = subs->last_delay - est_delay;
+ else
+ est_delay = subs->last_delay + est_delay;
+
if (est_delay < 0)
est_delay = 0;
return est_delay;
@@ -78,8 +83,7 @@
return SNDRV_PCM_POS_XRUN;
spin_lock(&subs->lock);
hwptr_done = subs->hwptr_done;
- if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
- substream->runtime->delay = snd_usb_pcm_delay(subs,
+ substream->runtime->delay = snd_usb_pcm_delay(subs,
substream->runtime->rate);
spin_unlock(&subs->lock);
return hwptr_done / (substream->runtime->frame_bits >> 3);
@@ -1147,6 +1151,10 @@
int i, period_elapsed = 0;
unsigned long flags;
unsigned char *cp;
+ int current_frame_number;
+
+ /* read frame number here, update pointer in critical section */
+ current_frame_number = usb_get_current_frame_number(subs->dev);
stride = runtime->frame_bits >> 3;
@@ -1180,6 +1188,15 @@
subs->transfer_done -= runtime->period_size;
period_elapsed = 1;
}
+ /* capture delay is by construction limited to one URB,
+ * reset delays here
+ */
+ runtime->delay = subs->last_delay = 0;
+
+ /* realign last_frame_number */
+ subs->last_frame_number = current_frame_number;
+ subs->last_frame_number &= 0xFF; /* keep 8 LSBs */
+
spin_unlock_irqrestore(&subs->lock, flags);
/* copy a data chunk */
if (oldptr + bytes > runtime->buffer_size * stride) {
