[alsa-devel] [PATCH] ASoC: davinci-mcasp: add support for unsigned PCM formats

[Ben Gardiner]

Although the McASP supports sign-extending samples in RX or TX [1]; the
davinci-mcasp driver does not touch the {R,X}PBIT or {R,X}PAD field of the
{R,X}FMT registers meaning that the McASP will serialize the bytes it is given
regardless of their signedness. So supporting unsigned formats is as simple
as adding them to the metadata of the davinci-mcasp driver.

Update the FMTBITs reported in the snd_soc_dai_driver and also update the case
statements in davinci-mcasp's hw_params() function so that the McASP can be
connected to CODECs that use unsigned values.

[1] http://www.ti.com/lit/ug/sprufm1/sprufm1.pdf

Signed-off-by: Ben Gardiner <bengardiner at nanometrics.ca>

---

Tested with a logic analyzer on da850evm where an unsigned 16bit codec was
registered with the mcasp and a 16bit signed file was played to it. ALSA's
plug pcm mapped to unsigned and the samples serialized as unsigned 16bit --
as expected.
---
 sound/soc/davinci/davinci-mcasp.c |   20 +++++++++++++-------
 1 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/sound/soc/davinci/davinci-mcasp.c b/sound/soc/davinci/davinci-mcasp.c
index 8566238..7173df2 100644
--- a/sound/soc/davinci/davinci-mcasp.c
+++ b/sound/soc/davinci/davinci-mcasp.c
@@ -732,16 +732,19 @@ static int davinci_mcasp_hw_params(struct snd_pcm_substream *substream,
 		davinci_hw_param(dev, substream->stream);
 
 	switch (params_format(params)) {
+	case SNDRV_PCM_FORMAT_U8:
 	case SNDRV_PCM_FORMAT_S8:
 		dma_params->data_type = 1;
 		word_length = DAVINCI_AUDIO_WORD_8;
 		break;
 
+	case SNDRV_PCM_FORMAT_U16_LE:
 	case SNDRV_PCM_FORMAT_S16_LE:
 		dma_params->data_type = 2;
 		word_length = DAVINCI_AUDIO_WORD_16;
 		break;
 
+	case SNDRV_PCM_FORMAT_U32_LE:
 	case SNDRV_PCM_FORMAT_S32_LE:
 		dma_params->data_type = 4;
 		word_length = DAVINCI_AUDIO_WORD_32;
@@ -818,6 +821,13 @@ static struct snd_soc_dai_ops davinci_mcasp_dai_ops = {
 
 };
 
+#define DAVINCI_MCASP_PCM_FMTS (SNDRV_PCM_FMTBIT_S8 | \
+				SNDRV_PCM_FMTBIT_U8 | \
+				SNDRV_PCM_FMTBIT_S16_LE | \
+				SNDRV_PCM_FMTBIT_U16_LE | \
+				SNDRV_PCM_FMTBIT_S32_LE | \
+				SNDRV_PCM_FMTBIT_U32_LE)
+
 static struct snd_soc_dai_driver davinci_mcasp_dai[] = {
 	{
 		.name		= "davinci-mcasp.0",
@@ -825,17 +835,13 @@ static struct snd_soc_dai_driver davinci_mcasp_dai[] = {
 			.channels_min	= 2,
 			.channels_max 	= 2,
 			.rates 		= DAVINCI_MCASP_RATES,
-			.formats 	= SNDRV_PCM_FMTBIT_S8 |
-						SNDRV_PCM_FMTBIT_S16_LE |
-						SNDRV_PCM_FMTBIT_S32_LE,
+			.formats	= DAVINCI_MCASP_PCM_FMTS,
 		},
 		.capture 	= {
 			.channels_min 	= 2,
 			.channels_max 	= 2,
 			.rates 		= DAVINCI_MCASP_RATES,
-			.formats	= SNDRV_PCM_FMTBIT_S8 |
-						SNDRV_PCM_FMTBIT_S16_LE |
-						SNDRV_PCM_FMTBIT_S32_LE,
+			.formats	= DAVINCI_MCASP_PCM_FMTS,
 		},
 		.ops 		= &davinci_mcasp_dai_ops,
 
@@ -846,7 +852,7 @@ static struct snd_soc_dai_driver davinci_mcasp_dai[] = {
 			.channels_min	= 1,
 			.channels_max	= 384,
 			.rates		= DAVINCI_MCASP_RATES,
-			.formats	= SNDRV_PCM_FMTBIT_S16_LE,
+			.formats	= DAVINCI_MCASP_PCM_FMTS,
 		},
 		.ops 		= &davinci_mcasp_dai_ops,
 	},
-- 
1.7.4.1