[alsa-devel] [topic/asoc][RFC 1/1] ASoC: OMAP: Add support for mono link configuration to McBSP DAI

[Jarkko Nikula]

Patch adds support for mono audio link configuration to function
omap_mcbsp_dai_hw_params but doesn't expose it in omap_mcbsp_dai table by
default.

Main idea behind this is to allow operate with real mono codecs but not
break compatibility with existing codecs which can expose their channels_min
as 1. Machine driver can use functionality provided by this patch by
re-configuring runtime DAI's channels_min and channel_max to 1 for a link
having mono codec.

For mono link, the I2S signalling remains the same but only first frame
(left channel) is transmitting audio data and second frame is having a
null data. In DSP_A, only first frame is transmitted.

Signed-off-by: Jarkko Nikula <jarkko.nikula at nokia.com>
---
 sound/soc/omap/omap-mcbsp.c |   19 ++++++++++++-------
 1 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/sound/soc/omap/omap-mcbsp.c b/sound/soc/omap/omap-mcbsp.c
index 2eeb135..bb05c76 100644
--- a/sound/soc/omap/omap-mcbsp.c
+++ b/sound/soc/omap/omap-mcbsp.c
@@ -203,7 +203,7 @@ static int omap_mcbsp_dai_hw_params(struct snd_pcm_substream *substream,
 	struct omap_mcbsp_data *mcbsp_data = to_mcbsp(cpu_dai->private_data);
 	struct omap_mcbsp_reg_cfg *regs = &mcbsp_data->regs;
 	int dma, bus_id = mcbsp_data->bus_id, id = cpu_dai->id;
-	int wlen;
+	int wlen, channels;
 	unsigned long port;
 
 	if (cpu_class_is_omap1()) {
@@ -232,12 +232,17 @@ static int omap_mcbsp_dai_hw_params(struct snd_pcm_substream *substream,
 		return 0;
 	}
 
-	switch (params_channels(params)) {
+	channels = params_channels(params);
+	switch (channels) {
 	case 2:
-		/* Set 1 word per (McBPSP) frame and use dual-phase frames */
-		regs->rcr2	|= RFRLEN2(1 - 1) | RPHASE;
+		/* Use dual-phase frames */
+		regs->rcr2	|= RPHASE;
+		regs->xcr2	|= XPHASE;
+	case 1:
+		/* Set 1 word per (McBSP) frame */
+		regs->rcr2	|= RFRLEN2(1 - 1);
 		regs->rcr1	|= RFRLEN1(1 - 1);
-		regs->xcr2	|= XFRLEN2(1 - 1) | XPHASE;
+		regs->xcr2	|= XFRLEN2(1 - 1);
 		regs->xcr1	|= XFRLEN1(1 - 1);
 		break;
 	default:
@@ -266,8 +271,8 @@ static int omap_mcbsp_dai_hw_params(struct snd_pcm_substream *substream,
 		regs->srgr1	|= FWID(wlen - 1);
 		break;
 	case SND_SOC_DAIFMT_DSP_A:
-		regs->srgr2	|= FPER(wlen * 2 - 1);
-		regs->srgr1	|= FWID(wlen * 2 - 2);
+		regs->srgr2	|= FPER(wlen * channels - 1);
+		regs->srgr1	|= FWID(wlen * channels - 2);
 		break;
 	}
 
-- 
1.5.6.5