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

[Codrin.Ciubotariu at microchip.com]

On 25.07.2019 21:24, mirq-linux at rere.qmqm.pl wrote:
> External E-Mail
> 
> 
> 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?

Best regards,
Codrin