ASoC: davinci-mcasp: Support for one channel (mono) audio

Mono audio can be achieved by configuring McASP to transmit/receive only
during one timeslot. McASP will still going to generate clocks for the
other slot(s), but will only use the single slot to transmit/receive.
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/davinci/davinci-mcasp.c

@@ -629,7 +629,7 @@ static int davinci_mcasp_ch_constraint(struct davinci_mcasp *mcasp, int stream,
 	if (mcasp->tdm_mask[stream])
 		slots = hweight32(mcasp->tdm_mask[stream]);
 
-	for (i = 2; i <= slots; i++)
+	for (i = 1; i <= slots; i++)
 		list[count++] = i;
 
 	for (i = 2; i <= serializers; i++)
@@ -1297,7 +1297,7 @@ static int davinci_mcasp_startup(struct snd_pcm_substream *substream,
 
 	snd_pcm_hw_constraint_minmax(substream->runtime,
 				     SNDRV_PCM_HW_PARAM_CHANNELS,
-				     2, max_channels);
+				     0, max_channels);
 
 	snd_pcm_hw_constraint_list(substream->runtime,
 				   0, SNDRV_PCM_HW_PARAM_CHANNELS,
@@ -1459,13 +1459,13 @@ static struct snd_soc_dai_driver davinci_mcasp_dai[] = {
 		.suspend	= davinci_mcasp_suspend,
 		.resume		= davinci_mcasp_resume,
 		.playback	= {
-			.channels_min	= 2,
+			.channels_min	= 1,
 			.channels_max	= 32 * 16,
 			.rates 		= DAVINCI_MCASP_RATES,
 			.formats	= DAVINCI_MCASP_PCM_FMTS,
 		},
 		.capture 	= {
-			.channels_min 	= 2,
+			.channels_min 	= 1,
 			.channels_max	= 32 * 16,
 			.rates 		= DAVINCI_MCASP_RATES,
 			.formats	= DAVINCI_MCASP_PCM_FMTS,
@@ -1971,12 +1971,12 @@ static int davinci_mcasp_probe(struct platform_device *pdev)
 	 */
 	mcasp->chconstr[SNDRV_PCM_STREAM_PLAYBACK].list =
 		devm_kzalloc(mcasp->dev, sizeof(unsigned int) *
-			     (32 + mcasp->num_serializer - 2),
+			     (32 + mcasp->num_serializer - 1),
 			     GFP_KERNEL);
 
 	mcasp->chconstr[SNDRV_PCM_STREAM_CAPTURE].list =
 		devm_kzalloc(mcasp->dev, sizeof(unsigned int) *
-			     (32 + mcasp->num_serializer - 2),
+			     (32 + mcasp->num_serializer - 1),
 			     GFP_KERNEL);
 
 	if (!mcasp->chconstr[SNDRV_PCM_STREAM_PLAYBACK].list ||