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ALSA: core: group read of pointer, tstamp and jiffies

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Group read of hw_ptr, tstamp and jiffies in a sequence
for better correlation. Previous code took timestamp at the
end, which could introduce delays between audio time and
system time.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Pierre-Louis Bossart 2012-05-22 14:54:02 -05:00 committed by Takashi Iwai
parent 599ed4b0ae
commit 3509a03f4d
1 changed files with 18 additions and 5 deletions
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23
sound/core/pcm_lib.c
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@ -313,9 +313,22 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream,
snd_pcm_uframes_t old_hw_ptr, new_hw_ptr, hw_base;
snd_pcm_sframes_t hdelta, delta;
unsigned long jdelta;
unsigned long curr_jiffies;
struct timespec curr_tstamp;
old_hw_ptr = runtime->status->hw_ptr;
/*
* group pointer, time and jiffies reads to allow for more
* accurate correlations/corrections.
* The values are stored at the end of this routine after
* corrections for hw_ptr position
*/
pos = substream->ops->pointer(substream);
curr_jiffies = jiffies;
if (runtime->tstamp_mode == SNDRV_PCM_TSTAMP_ENABLE)
snd_pcm_gettime(runtime, (struct timespec *)&curr_tstamp);
if (pos == SNDRV_PCM_POS_XRUN) {
xrun(substream);
return -EPIPE;
@ -343,7 +356,7 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream,
delta = runtime->hw_ptr_interrupt + runtime->period_size;
if (delta > new_hw_ptr) {
/* check for double acknowledged interrupts */
hdelta = jiffies - runtime->hw_ptr_jiffies;
hdelta = curr_jiffies - runtime->hw_ptr_jiffies;
if (hdelta > runtime->hw_ptr_buffer_jiffies/2) {
hw_base += runtime->buffer_size;
if (hw_base >= runtime->boundary)
@ -388,7 +401,7 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream,
* Without regular period interrupts, we have to check
* the elapsed time to detect xruns.
*/
jdelta = jiffies - runtime->hw_ptr_jiffies;
jdelta = curr_jiffies - runtime->hw_ptr_jiffies;
if (jdelta < runtime->hw_ptr_buffer_jiffies / 2)
goto no_delta_check;
hdelta = jdelta - delta * HZ / runtime->rate;
@ -430,7 +443,7 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream,
if (hdelta < runtime->delay)
goto no_jiffies_check;
hdelta -= runtime->delay;
jdelta = jiffies - runtime->hw_ptr_jiffies;
jdelta = curr_jiffies - runtime->hw_ptr_jiffies;
if (((hdelta * HZ) / runtime->rate) > jdelta + HZ/100) {
delta = jdelta /
(((runtime->period_size * HZ) / runtime->rate)
@ -492,9 +505,9 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream,
}
runtime->hw_ptr_base = hw_base;
runtime->status->hw_ptr = new_hw_ptr;
runtime->hw_ptr_jiffies = jiffies;
runtime->hw_ptr_jiffies = curr_jiffies;
if (runtime->tstamp_mode == SNDRV_PCM_TSTAMP_ENABLE)
snd_pcm_gettime(runtime, (struct timespec *)&runtime->status->tstamp);
runtime->status->tstamp = curr_tstamp;
return snd_pcm_update_state(substream, runtime);
}