ASoC: mediatek: Increase periods_min in capture

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 <koro.chen@mediatek.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/sound/soc/mediatek/mtk-afe-pcm.c b/sound/soc/mediatek/mtk-afe-pcm.c
index d190fe017559b6a9ba40baff2f4dd8f05b88cb8e..f5baf3c38863f4eda4e31f2af8c612a6c23f3493 100644 (file)
--- 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)