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ALSA: ASoC: DaVinci: document I2S limitations

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DaVinci does not support true I2S or right justified
mode so not all I2S codecs will work with it when the codec is
master. Document this limitation.

Add dsp_a, dsp_b mode options

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 2008-12-19 13:05:24 -07:00 committed by Mark Brown
parent 69ab820c86
commit 07d8d9dca4
1 changed files with 19 additions and 2 deletions
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21
sound/soc/davinci/davinci-i2s.c
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@ -241,10 +241,27 @@ static int davinci_i2s_set_dai_fmt(struct snd_soc_dai *cpu_dai,
rcr = DAVINCI_MCBSP_RCR_RFRLEN1(1);
xcr = DAVINCI_MCBSP_XCR_XFIG | DAVINCI_MCBSP_XCR_XFRLEN1(1);
switch (fmt & SND_SOC_DAIFMT_FORMAT_MASK) {
case SND_SOC_DAIFMT_RIGHT_J:
case SND_SOC_DAIFMT_DSP_B:
break;
case SND_SOC_DAIFMT_I2S:
case SND_SOC_DAIFMT_DSP_B:
/* Davinci doesn't support TRUE I2S, but some codecs will have
* the left and right channels contiguous. This allows
* dsp_a mode to be used with an inverted normal frame clk.
* If your codec is master and does not have contiguous
* channels, then you will have sound on only one channel.
* Try using a different mode, or codec as slave.
*
* The TLV320AIC33 is an example of a codec where this works.
* It has a variable bit clock frequency allowing it to have
* valid data on every bit clock.
*
* The TLV320AIC23 is an example of a codec where this does not
* work. It has a fixed bit clock frequency with progressively
* more empty bit clock slots between channels as the sample
* rate is lowered.
*/
fmt ^= SND_SOC_DAIFMT_NB_IF;
case SND_SOC_DAIFMT_DSP_A:
rcr |= DAVINCI_MCBSP_RCR_RDATDLY(1);
xcr |= DAVINCI_MCBSP_XCR_XDATDLY(1);
break;