[alsa-devel] [PATCH 2/3] ASoC: omap-mcbsp: change the DSP_B mode to DSP_A mode

[Jarkko Nikula]

On Thu, 9 Apr 2009 12:16:55 +0200
"Ujfalusi Peter (Nokia-D/Tampere)" <peter.ujfalusi at nokia.com> wrote:

> > Are you absolutely sure on this? According to WM9713, it's the DSP_A
> > where MSB is valid after 1 bit clock period of the FS.
> 
> I think this is correct. The data is going to be valid exactly the
> same way, as the WM9713 data sheet describes.
> 
> As for the DSP_B mode: I think it can be implemented like this:
> Invert the frame sync polarity, Then:
> 	case SND_SOC_DAIFMT_DSP_B:
> 		regs->srgr2	|= FPER(wlen * channels - 1);
> 		regs->srgr1	|= FWID(0); /* FS pulse width is 1
> */ break;
> 
> So the MSB will be in the correct place.
> 
Peter is right. There is a bug in omap-mcbsp.c. If I play maximum
negative samples "aplay -f U8 /dev/zero", the MSB bit is then
just after the falling edge of FS like in DSP_A format... (hmm, what I
was doing in the commit bd25867a6cbe7a00ef7dbe8d9ddebc91b00b9b3f).

Is it ok to leave this over the easter to make sure next week that we'll
get this finally right? I have had already few DSP format fixes there
and still this is not correct... :-)

-- 
Jarkko