[PATCH v2 3/4] ASoC: davinci-mcasp: Constraint on the period and buffer size based on FIFO usage

[Peter Ujfalusi <peter.ujfalusi@ti.com>]

We need to place constraint on the period and buffer size if the read
or write AFIFO is enabled and it is configured for more than one word
otherwise the DMA will fail in buffer configuration where the sizes
are not aligned with the requested FIFO configuration.

Some application (like mplayer) needs the constraint placed on the
buffer size as well. If only period size is constrained they might
fail to figure out the allowed buffer configuration.

Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
---
 sound/soc/davinci/davinci-mcasp.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/sound/soc/davinci/davinci-mcasp.c b/sound/soc/davinci/davinci-mcasp.c
index a01ae97c90aa..3ca6e8c4568a 100644
--- a/sound/soc/davinci/davinci-mcasp.c
+++ b/sound/soc/davinci/davinci-mcasp.c
@@ -720,6 +720,7 @@ static int davinci_mcasp_startup(struct snd_pcm_substream *substream,
 				 struct snd_soc_dai *dai)
 {
 	struct davinci_mcasp *mcasp = snd_soc_dai_get_drvdata(dai);
+	int afifo_numevt;
 
 	if (mcasp->version == MCASP_VERSION_4)
 		snd_soc_dai_set_dma_data(dai, substream,
@@ -727,6 +728,21 @@ static int davinci_mcasp_startup(struct snd_pcm_substream *substream,
 	else
 		snd_soc_dai_set_dma_data(dai, substream, mcasp->dma_params);
 
+	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK)
+		afifo_numevt = mcasp->txnumevt;
+	else
+		afifo_numevt = mcasp->rxnumevt;
+
+	if (afifo_numevt > 1) {
+		snd_pcm_hw_constraint_step(substream->runtime, 0,
+					   SNDRV_PCM_HW_PARAM_PERIOD_SIZE,
+					   afifo_numevt);
+
+		snd_pcm_hw_constraint_step(substream->runtime, 0,
+					   SNDRV_PCM_HW_PARAM_BUFFER_SIZE,
+					   afifo_numevt);
+	}
+
 	return 0;
 }
 
-- 
1.9.0