[alsa-devel] [PATCH] ASoC: OMAP: Set minimum buffer size constraint for McBSP2 in OMAP3

[Jarkko Nikula]

Signed-off-by: Jarkko Nikula <jarkko.nikula at nokia.com>
---
 sound/soc/omap/omap-mcbsp.c |   11 +++++++++++
 1 files changed, 11 insertions(+), 0 deletions(-)

diff --git a/sound/soc/omap/omap-mcbsp.c b/sound/soc/omap/omap-mcbsp.c
index d6882be..9c09b94 100644
--- a/sound/soc/omap/omap-mcbsp.c
+++ b/sound/soc/omap/omap-mcbsp.c
@@ -146,6 +146,17 @@ static int omap_mcbsp_dai_startup(struct snd_pcm_substream *substream,
 	struct omap_mcbsp_data *mcbsp_data = to_mcbsp(cpu_dai->private_data);
 	int err = 0;
 
+	if (cpu_is_omap343x() && mcbsp_data->bus_id == 1) {
+		/*
+		 * McBSP2 in OMAP3 has 1024 * 32-bit internal audio buffer.
+		 * Set constraint for minimum buffer size to the same than FIFO
+		 * size in order to avoid underruns in playback startup because
+		 * HW is keeping the DMA request active until FIFO is filled.
+		 */
+		snd_pcm_hw_constraint_minmax(substream->runtime,
+			SNDRV_PCM_HW_PARAM_BUFFER_BYTES, 4096, UINT_MAX);
+	}
+
 	if (!cpu_dai->active)
 		err = omap_mcbsp_request(mcbsp_data->bus_id);
 
-- 
1.6.2