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Commit 3509a03f authored by Pierre-Louis Bossart's avatar Pierre-Louis Bossart Committed by Takashi Iwai
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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: default avatarPierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: default avatarTakashi Iwai <tiwai@suse.de>
parent 599ed4b0

sound/core/pcm_lib.c

+18 −5
Original line number Diff line number Diff line
@@ -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);

}