[alsa-devel] [PATCH RFC 3/9] ALSA: hda: read trigger_timestamp immediately after starting DMA

[Pierre-Louis Bossart]

Make sure wallclock counter and trigger timestamp are read very
close to each other for better alignment.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com>
---
 sound/pci/hda/hda_controller.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/sound/pci/hda/hda_controller.c b/sound/pci/hda/hda_controller.c
index 8337645..6a9f8c8 100644
--- a/sound/pci/hda/hda_controller.c
+++ b/sound/pci/hda/hda_controller.c
@@ -562,6 +562,8 @@ static int azx_pcm_trigger(struct snd_pcm_substream *substream, int cmd)
 	azx_dev = get_azx_dev(substream);
 	trace_azx_pcm_trigger(chip, azx_dev, cmd);
 
+	substream->runtime->trigger_tstamp_latched = 0;
+
 	if (dsp_is_locked(azx_dev) || !azx_dev->prepared)
 		return -EPIPE;
 
@@ -657,6 +659,9 @@ static int azx_pcm_trigger(struct snd_pcm_substream *substream, int cmd)
 		azx_writel(chip, SSYNC, azx_readl(chip, SSYNC) & ~sbits);
 	if (start) {
 		azx_timecounter_init(substream, 0, 0);
+		snd_pcm_gettime(substream->runtime, &substream->runtime->trigger_tstamp);
+		substream->runtime->trigger_tstamp_latched = 1;
+
 		if (nsync > 1) {
 			cycle_t cycle_last;
 
-- 
2.1.0