linux-kernel - [PATCH 5.6 014/167] ASoC: qcom: q6asm-dai: Add SNDRV_PCM_INFO

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Date:   Tue, 28 Apr 2020 20:23:10 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Stephan Gerhold <stephan@...hold.net>,
        Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        Mark Brown <broonie@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.6 014/167] ASoC: qcom: q6asm-dai: Add SNDRV_PCM_INFO_BATCH flag

From: Stephan Gerhold <stephan@...hold.net>

[ Upstream commit 7f2430cda819a9ecb1df5a0f3ef4f1c20db3f811 ]

At the moment, playing audio with PulseAudio with the qdsp6 driver
results in distorted sound. It seems like its timer-based scheduling
does not work properly with qdsp6 since setting tsched=0 in
the PulseAudio configuration avoids the issue.

Apparently this happens when the pointer() callback is not accurate
enough. There is a SNDRV_PCM_INFO_BATCH flag that can be used to stop
PulseAudio from using timer-based scheduling by default.

According to https://www.alsa-project.org/pipermail/alsa-devel/2014-March/073816.html:

    The flag is being used in the sense explained in the previous audio
    meeting -- the data transfer granularity isn't fine enough but aligned
    to the period size (or less).

q6asm-dai reports the position as multiple of

    prtd->pcm_count = snd_pcm_lib_period_bytes(substream)

so it indeed just a multiple of the period size.

Therefore adding the flag here seems appropriate and makes audio
work out of the box.

Fixes: 2a9e92d371db ("ASoC: qdsp6: q6asm: Add q6asm dai driver")
Signed-off-by: Stephan Gerhold <stephan@...hold.net>
Reviewed-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Cc: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
Link: https://lore.kernel.org/r/20200330175210.47518-1-stephan@gerhold.net
Signed-off-by: Mark Brown <broonie@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 sound/soc/qcom/qdsp6/q6asm-dai.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sound/soc/qcom/qdsp6/q6asm-dai.c b/sound/soc/qcom/qdsp6/q6asm-dai.c
index c0d422d0ab94f..d7dc80ede8927 100644
--- a/sound/soc/qcom/qdsp6/q6asm-dai.c
+++ b/sound/soc/qcom/qdsp6/q6asm-dai.c
@@ -73,7 +73,7 @@ struct q6asm_dai_data {
 };
 
 static const struct snd_pcm_hardware q6asm_dai_hardware_capture = {
-	.info =                 (SNDRV_PCM_INFO_MMAP |
+	.info =                 (SNDRV_PCM_INFO_MMAP | SNDRV_PCM_INFO_BATCH |
 				SNDRV_PCM_INFO_BLOCK_TRANSFER |
 				SNDRV_PCM_INFO_MMAP_VALID |
 				SNDRV_PCM_INFO_INTERLEAVED |
@@ -95,7 +95,7 @@ static const struct snd_pcm_hardware q6asm_dai_hardware_capture = {
 };
 
 static struct snd_pcm_hardware q6asm_dai_hardware_playback = {
-	.info =                 (SNDRV_PCM_INFO_MMAP |
+	.info =                 (SNDRV_PCM_INFO_MMAP | SNDRV_PCM_INFO_BATCH |
 				SNDRV_PCM_INFO_BLOCK_TRANSFER |
 				SNDRV_PCM_INFO_MMAP_VALID |
 				SNDRV_PCM_INFO_INTERLEAVED |
-- 
2.20.1