RE: [alsa-devel] [PATCH] ASoC: atmel_ssc_dai: Track playback and capture CMR dividers separately.

[Peter Rosin <peda@axentia.se>]

Bo Chen wrote:
> with this piece of code, I reproduce your issue.
> 
> Now, I know the reason of this issue, work in oss mode, it will set the default
> clock to 8KHz, and then if change to other sample rate, for example 48KHz,
> the div is different, then it reports -EBUSY.

Indeed.

> So, I think we won't change the ATMEL_SSC_CMR_DIV to
> ATMEL_SSC_TCMR_DIV and ATMEL_SSC_RCMR_DIV, as it will affect other
> users. We just deal with this situation in ATMEL_SSC_CMR_DIV block, check
> the direction, if the same direction change the div, then accept the change,
> otherwise, return -EBUSY.

Ok.

But I'm not sure it is possible to dig out the current direction in the
.set_clkdiv callback? Perhaps the correct fix is to set the bits
.symmetric_rates, .symmetric_channels and .symmetric_samplebits
in the atmel_ssc_dai struct when the ssc dai is master? Then I
expect that other mechanisms will kick in that will render the current
CMR_DIV check pointless?

Is a dai driver allowed to change these symmetry bits after registration?
Can they be set in the .set_sysclk callback? Perhaps in the
ATMEL_SSC_CMR_DIV block itself? That callback should only be
called when the dai is master, so that would be perfect...

Yes, the limitation would be a little bit more strict than today, but is it
really common to require different modes on playback and capture?

Cheers,
Peter