[RFC][PATCH] ALSA: pcm_dmaengine: Use more shorter periods for SEGMENT granularity PCM DMA

[Marek Vasut <marex@nabladev.com>]

The segment granularity PCM DMA updates PCM pointer at the end of every
segment. In case the segments are too long, which happens with pipewire,
it may happen that pcm_lib wait_for_avail() will time out while waiting
for PCM pointer update and playback will fail with IO error.

In case of SEGMENT granularity, use 8 shorter segments over the default
2 long segments set in dmaengine_pcm_set_runtime_hwparams(). That gives
the DMA engine some chance to update the PCM pointer every once in a
while and prevent the timeout.

Signed-off-by: Marek Vasut <marex@nabladev.com>
---
Cc: Jaroslav Kysela <perex@perex.cz>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Mark Brown <broonie@kernel.org>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Takashi Iwai <tiwai@suse.com>
Cc: linux-sound@vger.kernel.org
---
 sound/core/pcm_dmaengine.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/sound/core/pcm_dmaengine.c b/sound/core/pcm_dmaengine.c
index 1306b04be171a..092ce958e1aee 100644
--- a/sound/core/pcm_dmaengine.c
+++ b/sound/core/pcm_dmaengine.c
@@ -424,6 +424,10 @@ int snd_dmaengine_pcm_refine_runtime_hwparams(
 			hw->info |= SNDRV_PCM_INFO_PAUSE | SNDRV_PCM_INFO_RESUME;
 		if (dma_caps.residue_granularity <= DMA_RESIDUE_GRANULARITY_SEGMENT)
 			hw->info |= SNDRV_PCM_INFO_BATCH;
+		if (dma_caps.residue_granularity == DMA_RESIDUE_GRANULARITY_SEGMENT) {
+			hw->periods_min = 8;
+			hw->period_bytes_max /= 8;
+		}
 
 		if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
 			addr_widths = dma_caps.dst_addr_widths;
-- 
2.53.0