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ALSA: snd-usb: restore delay information 

Parts of commit 294c4fb8 ("ALSA: usb: refine delay information with USB
frame counter") were unfortunately lost during the refactoring of the
snd-usb driver in 3.5.

This patch adds them back, restoring the correct delay information
behaviour.

Signed-off-by: Daniel Mack <zonque@gmail.com>
Cc: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Cc: stable@kernel.org [3.5+]
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Daniel Mack 2012-08-30 18:52:29 +02:00 committed by Takashi Iwai
parent 03d2f44e96
commit fbcfbf5f67
1 changed files with 26 additions and 3 deletions
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29
sound/usb/pcm.c
View File

@ -1091,7 +1091,16 @@ static void prepare_playback_urb(struct snd_usb_substream *subs,
subs->hwptr_done += bytes;
if (subs->hwptr_done >= runtime->buffer_size * stride)
subs->hwptr_done -= runtime->buffer_size * stride;
/* update delay with exact number of samples queued */
runtime->delay = subs->last_delay;
runtime->delay += frames;
subs->last_delay = runtime->delay;
/* realign last_frame_number */
subs->last_frame_number = usb_get_current_frame_number(subs->dev);
subs->last_frame_number &= 0xFF; /* keep 8 LSBs */
spin_unlock_irqrestore(&subs->lock, flags);
urb->transfer_buffer_length = bytes;
if (period_elapsed)
@ -1109,12 +1118,26 @@ static void retire_playback_urb(struct snd_usb_substream *subs,
struct snd_pcm_runtime *runtime = subs->pcm_substream->runtime;
int stride = runtime->frame_bits >> 3;
int processed = urb->transfer_buffer_length / stride;
int est_delay;
spin_lock_irqsave(&subs->lock, flags);
if (processed > runtime->delay)
runtime->delay = 0;
est_delay = snd_usb_pcm_delay(subs, runtime->rate);
/* update delay with exact number of samples played */
if (processed > subs->last_delay)
subs->last_delay = 0;
else
runtime->delay -= processed;
subs->last_delay -= processed;
runtime->delay = subs->last_delay;
/*
* Report when delay estimate is off by more than 2ms.
* The error should be lower than 2ms since the estimate relies
* on two reads of a counter updated every ms.
*/
if (abs(est_delay - subs->last_delay) * 1000 > runtime->rate * 2)
snd_printk(KERN_DEBUG "delay: estimated %d, actual %d\n",
est_delay, subs->last_delay);
spin_unlock_irqrestore(&subs->lock, flags);
}