[PATCH] ALSA: pcm: Update hardware pointer before start capture

From: Ricardo Biehl Pasquali <pasqualirb@gmail.com>
To: alsa-devel@alsa-project.org
Cc: tiwai@suse.de
Subject: [PATCH] ALSA: pcm: Update hardware pointer before start capture
Date: Fri, 7 Sep 2018 16:58:54 -0300	[thread overview]
Message-ID: <20180907195854.GA17424@localhost.localdomain> (raw)

This ensures the transfer loop won't waste a run to read
the few frames (if any) between start and hw_ptr update.
It will wait for the next interrupt with wait_for_avail().

Signed-off-by: Ricardo Biehl Pasquali <pasqualirb@gmail.com>
---
 sound/core/pcm_lib.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index 7f71c2449..40013b26f 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -2172,6 +2172,10 @@ snd_pcm_sframes_t __snd_pcm_lib_xfer(struct snd_pcm_substream *substream,
 	if (err < 0)
 		goto _end_unlock;
 
+	runtime->twake = runtime->control->avail_min ? : 1;
+	if (runtime->status->state == SNDRV_PCM_STATE_RUNNING)
+		snd_pcm_update_hw_ptr(substream);
+
 	if (!is_playback &&
 	    runtime->status->state == SNDRV_PCM_STATE_PREPARED) {
 		if (size >= runtime->start_threshold) {
@@ -2185,10 +2189,8 @@ snd_pcm_sframes_t __snd_pcm_lib_xfer(struct snd_pcm_substream *substream,
 		}
 	}
 
-	runtime->twake = runtime->control->avail_min ? : 1;
-	if (runtime->status->state == SNDRV_PCM_STATE_RUNNING)
-		snd_pcm_update_hw_ptr(substream);
 	avail = snd_pcm_avail(substream);
+
 	while (size > 0) {
 		snd_pcm_uframes_t frames, appl_ptr, appl_ofs;
 		snd_pcm_uframes_t cont;
-- 
2.17.1
