aboutsummaryrefslogtreecommitdiff
path: root/sound
diff options
context:
space:
mode:
authorPierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>2012-05-22 14:54:02 -0500
committerTakashi Iwai <tiwai@suse.de>2012-05-23 01:50:29 +0200
commit3509a03f4dcf7fedb8880180fed3f7f791ce5598 (patch)
tree9be4d6f21e9fe84926b96b39fbb825c537168011 /sound
parent599ed4b0aeceb6d45ea33f64639e745e3da72766 (diff)
downloadlinux-3509a03f4dcf7fedb8880180fed3f7f791ce5598.tar.gz
ALSA: core: group read of pointer, tstamp and jiffies
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>
Diffstat (limited to 'sound')
-rw-r--r--sound/core/pcm_lib.c23
1 files changed, 18 insertions, 5 deletions
diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index faedb1481b2..8f312fa6c28 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -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);
}