[alsa-devel] [PATCH] ASoC: tlv320aic3x: Correct S24_3LE support

[Peter Ujfalusi]

On 06/09/2014 11:24 PM, Mark Brown wrote:
> On Fri, Jun 06, 2014 at 04:05:31PM +0300, Peter Ujfalusi wrote:
> 
>> Correct the hw_params callback to configure the codec correctly in case of
>> S24_3LE format.
>> S24_LE is not defined as supported format for the codec.
> 
> These should both be supported by the time things get down to the wire -
> the memory layout shouldn't matter.

The codec itself has support for 16, 20, 24 and 32 bits data. The
AIC3X_FORMATS is correct:
#define AIC3X_FORMATS (SNDRV_PCM_FMTBIT_S16_LE | SNDRV_PCM_FMTBIT_S20_3LE | \
			SNDRV_PCM_FMTBIT_S24_3LE | SNDRV_PCM_FMTBIT_S32_LE)

While in hw_params the switch was not handling the S24_3LE but it was defined
as S24_LE. So the code was not correct: It advertised that it supportsd
S24_3LE and was not handling it, but it was handling S24_LE which would not
happen with this codec driver since the format is not supported - as it was
defined by the AIC3X_FORMATS.

This is a fix for the current driver.

> I really need to get round to doing
> the rest of the conversions to use params_width() which should ensure
> this.

Not sure how this would work at the end to be honest for all platforms and codecs.
How should the bitclock need to be configured for S24_3LE, S24_LE and S32_LE
msbits=24? They are at the end have 24bits audio data but in memory they are
stored in different ways.
Aic3x for example need to be configured to 24bit mode (24 clocks/channel if it
is master) so it is going to 'pull' that amount from the CPU side. This can
not be used with OMAP's sDMA/McBSP but davinci's eDMA/McASP can support it. I
can even get daVinci to 'extract' the valid 24 bits from the 32bit sample
coming via eDMA (mask/rotate/reverse operation).

So I still think that this is a bit more complicated than it looks

-- 
Péter