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

[mirq-linux at rere.qmqm.pl]

On Fri, Jul 26, 2019 at 10:33:29AM +0000, Codrin.Ciubotariu at microchip.com wrote:
> On 25.07.2019 21:24, mirq-linux at rere.qmqm.pl wrote:
> > 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.
> 
> I know, but there are other platforms with SSC, which don't have this 
> errata, like sam9x35 or sama5d3. Have you tested this mode, RK input, RF 
> input, RD starts on edge detect, TF input, TD starts synchronously with 
> receiver?

No, I have only SAMA5D2 available to test.

Best Regards,
Michał Mirosław