linux-kernel - [PATCH AUTOSEL 4.19 052/167] ALSA: pcm: Update hardware pointer before start capture

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Message-Id: <20190903162519.7136-52-sashal@kernel.org>
Date:   Tue,  3 Sep 2019 12:23:24 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Ricardo Biehl Pasquali <pasqualirb@...il.com>,
        Takashi Iwai <tiwai@...e.de>, Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 4.19 052/167] ALSA: pcm: Update hardware pointer before start capture

From: Ricardo Biehl Pasquali <pasqualirb@...il.com>

[ Upstream commit 64b6acf60b665fffd419c23886a1cbeeb253cfb4 ]

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@...il.com>
Signed-off-by: Takashi Iwai <tiwai@...e.de>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 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 7f71c2449af5e..40013b26f6719 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;
-- 
2.20.1