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ALSA: ASoC: DaVinci: davinci-i2s add comments to explain polarity 

Document the current polarity choices.

Signed-off-by: Troy Kisky <troy.kisky@boundarydevices.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
This commit is contained in:
Troy Kisky 2008-12-18 12:36:41 -07:00 committed by Mark Brown
parent 1152a1959f
commit 664b4af859
1 changed files with 36 additions and 0 deletions
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36
sound/soc/davinci/davinci-i2s.c
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@ -235,18 +235,45 @@ static int davinci_i2s_set_dai_fmt(struct snd_soc_dai *cpu_dai,
switch (fmt & SND_SOC_DAIFMT_INV_MASK) {
case SND_SOC_DAIFMT_IB_NF:
/* CLKRP Receive clock polarity,
* 1 - sampled on rising edge of CLKR
* valid on rising edge
* CLKXP Transmit clock polarity,
* 1 - clocked on falling edge of CLKX
* valid on rising edge
* FSRP Receive frame sync pol, 0 - active high
* FSXP Transmit frame sync pol, 0 - active high
*/
w = davinci_mcbsp_read_reg(dev, DAVINCI_MCBSP_PCR_REG);
MOD_REG_BIT(w, DAVINCI_MCBSP_PCR_CLKXP |
DAVINCI_MCBSP_PCR_CLKRP, 1);
davinci_mcbsp_write_reg(dev, DAVINCI_MCBSP_PCR_REG, w);
break;
case SND_SOC_DAIFMT_NB_IF:
/* CLKRP Receive clock polarity,
* 0 - sampled on falling edge of CLKR
* valid on falling edge
* CLKXP Transmit clock polarity,
* 0 - clocked on rising edge of CLKX
* valid on falling edge
* FSRP Receive frame sync pol, 1 - active low
* FSXP Transmit frame sync pol, 1 - active low
*/
w = davinci_mcbsp_read_reg(dev, DAVINCI_MCBSP_PCR_REG);
MOD_REG_BIT(w, DAVINCI_MCBSP_PCR_FSXP |
DAVINCI_MCBSP_PCR_FSRP, 1);
davinci_mcbsp_write_reg(dev, DAVINCI_MCBSP_PCR_REG, w);
break;
case SND_SOC_DAIFMT_IB_IF:
/* CLKRP Receive clock polarity,
* 1 - sampled on rising edge of CLKR
* valid on rising edge
* CLKXP Transmit clock polarity,
* 1 - clocked on falling edge of CLKX
* valid on rising edge
* FSRP Receive frame sync pol, 1 - active low
* FSXP Transmit frame sync pol, 1 - active low
*/
w = davinci_mcbsp_read_reg(dev, DAVINCI_MCBSP_PCR_REG);
MOD_REG_BIT(w, DAVINCI_MCBSP_PCR_CLKXP |
DAVINCI_MCBSP_PCR_CLKRP |
@ -255,6 +282,15 @@ static int davinci_i2s_set_dai_fmt(struct snd_soc_dai *cpu_dai,
davinci_mcbsp_write_reg(dev, DAVINCI_MCBSP_PCR_REG, w);
break;
case SND_SOC_DAIFMT_NB_NF:
/* CLKRP Receive clock polarity,
* 0 - sampled on falling edge of CLKR
* valid on falling edge
* CLKXP Transmit clock polarity,
* 0 - clocked on rising edge of CLKX
* valid on falling edge
* FSRP Receive frame sync pol, 0 - active high
* FSXP Transmit frame sync pol, 0 - active high
*/
break;
default:
return -EINVAL;