ASoC: qcom: q6asm-dai: Add SNDRV_PCM_INFO_BATCH flag

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: 2a9e92d ("ASoC: qdsp6: q6asm: Add q6asm dai driver")
Signed-off-by: Stephan Gerhold <[email protected]>
Reviewed-by: Srinivas Kandagatla <[email protected]>
Cc: Srinivas Kandagatla <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Mark Brown <[email protected]>

sound/soc/qcom/qdsp6/q6asm-dai.c

@@ -78,7 +78,7 @@ 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 |
@@ -100,7 +100,7 @@ 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 |