[PATCH] ASoC: Intel: bxt: Refine the HW contraint of Ref capture.

[Harry Pan]

The patch restricts the HW contraint of the refcap of WoV stream
in single channel (mono) and 16k Hz based on platform implementation.

Such that, the userspace program can rely on correct HW parameters
through the ALSA library call to manipulate the device.

Signed-off-by: Harry Pan <harry.pan@xxxxxxxxx>
---
 sound/soc/intel/boards/bxt_da7219_max98357a.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/sound/soc/intel/boards/bxt_da7219_max98357a.c b/sound/soc/intel/boards/bxt_da7219_max98357a.c
index ce35ec7884d1..382f71228807 100644
--- a/sound/soc/intel/boards/bxt_da7219_max98357a.c
+++ b/sound/soc/intel/boards/bxt_da7219_max98357a.c
@@ -338,8 +338,23 @@ static const struct snd_pcm_hw_constraint_list constraints_16000 = {
 	.list  = rates_16000,
 };
 
+static const unsigned int ch_mono[] = {
+	1,
+};
+
+static const struct snd_pcm_hw_constraint_list constraints_refcap = {
+	.count = ARRAY_SIZE(ch_mono),
+	.list  = ch_mono,
+};
+
 static int broxton_refcap_startup(struct snd_pcm_substream *substream)
 {
+	substream->runtime->hw.channels_max = 1;
+
+	snd_pcm_hw_constraint_list(substream->runtime, 0,
+					SNDRV_PCM_HW_PARAM_CHANNELS,
+					&constraints_refcap);
+
 	return snd_pcm_hw_constraint_list(substream->runtime, 0,
 			SNDRV_PCM_HW_PARAM_RATE,
 			&constraints_16000);
-- 
2.13.5