In capture, there is chance that hw_ptr reported at IRQ is
a little smaller than period_size due to internal AFE buffer.
In the case of ping-pong buffer:
|xxxxxxxxxxxxxxxxxxxxxxxxxxxx--|-----------------------------|
hw_ptr < period_size
This available buffer will not be read since its size is smaller than
avail_min (which is period_size by default), and read thread continues
to sleep. If the next hw_ptr is just a little larger than buffer_size,
overrun occurs. One more period can hold the possible unread buffer.
Signed-off-by: Koro Chen <[email protected]>
---
sound/soc/mediatek/mtk-afe-pcm.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
diff --git a/sound/soc/mediatek/mtk-afe-pcm.c b/sound/soc/mediatek/mtk-afe-pcm.c
index d190fe0..f5baf3c 100644
--- a/sound/soc/mediatek/mtk-afe-pcm.c
+++ b/sound/soc/mediatek/mtk-afe-pcm.c
@@ -549,6 +549,23 @@ static int mtk_afe_dais_startup(struct snd_pcm_substream
*substream,
memif->substream = substream;
snd_soc_set_runtime_hwparams(substream, &mtk_afe_hardware);
+
+ /*
+ * Capture cannot use ping-pong buffer since hw_ptr at IRQ may be
+ * smaller than period_size due to AFE's internal buffer.
+ * This easily leads to overrun when avail_min is period_size.
+ * One more period can hold the possible unread buffer.
+ */
+ if (substream->stream == SNDRV_PCM_STREAM_CAPTURE) {
+ ret = snd_pcm_hw_constraint_minmax(runtime,
+ SNDRV_PCM_HW_PARAM_PERIODS,
+ 3,
+
mtk_afe_hardware.periods_max);
+ if (ret < 0) {
+ dev_err(afe->dev, "hw_constraint_minmax failed\n");
+ return ret;
+ }
+ }
ret = snd_pcm_hw_constraint_integer(runtime,
SNDRV_PCM_HW_PARAM_PERIODS);
if (ret < 0)
--
1.7.9.5
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