[alsa-devel] [PATCH 5/5] ASoC: atmel_ssc_dai: Enable shared FSYNC source in frame-slave mode

[mirq-linux at rere.qmqm.pl]

On Thu, Jul 25, 2019 at 03:02:34PM +0000, Codrin.Ciubotariu at microchip.com wrote:
> On 22.07.2019 21:27, Michał Mirosław wrote:
> > SSC driver allows only synchronous TX and RX. In slave mode for BCLK
> > it uses only one of TK or RK pin, but for LRCLK it configured separate
> > inputs from TF and RF pins. Allow configuration with common FS signal.
[...]
> > @@ -613,10 +607,30 @@ static int atmel_ssc_hw_params(struct snd_pcm_substream *substream,
> >   		return -EINVAL;
> >   	}
> >   
> > -	if (!atmel_ssc_cfs(ssc_p)) {
> > +	if (atmel_ssc_cfs(ssc_p)) {
> > +		/*
> > +		 * SSC provides LRCLK
> > +		 *
> > +		 * Both TF and RF are generated, so use them directly.
> > +		 */
> > +		rcmr |=	  SSC_BF(RCMR_START, fs_edge);
> > +		tcmr |=	  SSC_BF(TCMR_START, fs_edge);
> > +	} else {
> >   		fslen = fslen_ext = 0;
> >   		rcmr_period = tcmr_period = 0;
> >   		fs_osync = SSC_FSOS_NONE;
> > +		if (!ssc->shared_fs_pin) {
> > +			rcmr |=	  SSC_BF(RCMR_START, fs_edge);
> > +			tcmr |=	  SSC_BF(TCMR_START, fs_edge);
> > +		} else if (ssc->clk_from_rk_pin) {
> > +			/* assume RF is to be used when RK is used as BCLK input */
> > +			/* Note: won't work correctly on SAMA5D2 due to errata */
> > +			rcmr |=	  SSC_BF(RCMR_START, fs_edge);
> > +			tcmr |=	  SSC_BF(TCMR_START, SSC_START_RECEIVE);
> 
> Did you find a platform in which this mode works?

To be exact: according to the errata, TX is delayed improperly. So if you
use only RX (SSC side receives) direction, you're fine.

Best Regards,
Michał Mirosław