linux-kernel - Re: [PATCH v2 6/6] ASoC: atmel_ssc_dai: Enable shared FSYNC source in frame-slave mode

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Date:   Mon, 26 Aug 2019 15:05:06 +0000
From:   <Codrin.Ciubotariu@...rochip.com>
To:     <mirq-linux@...e.qmqm.pl>, <alsa-devel@...a-project.org>,
        <devicetree@...r.kernel.org>
CC:     <alexandre.belloni@...tlin.com>, <arnd@...db.de>,
        <3chas3@...il.com>, <gregkh@...uxfoundation.org>, <perex@...ex.cz>,
        <lgirdwood@...il.com>, <Ludovic.Desroches@...rochip.com>,
        <broonie@...nel.org>, <mark.rutland@....com>,
        <Nicolas.Ferre@...rochip.com>, <robh-dt@...nel.org>,
        <tiwai@...e.com>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 6/6] ASoC: atmel_ssc_dai: Enable shared FSYNC source in
 frame-slave mode

On 24.08.2019 23:26, 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.
> 
> Signed-off-by: Michał Mirosław <mirq-linux@...e.qmqm.pl>
> 
> ---
>   v2: use alternate DT binding
>       split DT and drivers/misc changes
> 
> ---
>   sound/soc/atmel/atmel_ssc_dai.c | 26 ++++++++++++++++++++++----
>   1 file changed, 22 insertions(+), 4 deletions(-)
> 
> diff --git a/sound/soc/atmel/atmel_ssc_dai.c b/sound/soc/atmel/atmel_ssc_dai.c
> index 48e9eef34c0f..035d4da58f2b 100644
> --- a/sound/soc/atmel/atmel_ssc_dai.c
> +++ b/sound/soc/atmel/atmel_ssc_dai.c
> @@ -605,14 +605,32 @@ 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);

Hmm, how would this work if capture and playback start/run at the same time?

> +	} else {
>   		fslen = fslen_ext = 0;
>   		rcmr_period = tcmr_period = 0;
>   		fs_osync = SSC_FSOS_NONE;
> -	}
>   
> -	rcmr |=	  SSC_BF(RCMR_START, fs_edge);
> -	tcmr |=	  SSC_BF(TCMR_START, fs_edge);
> +		if (ssc->lrclk_from_tf_pin) {
> +			rcmr |=	  SSC_BF(RCMR_START, SSC_START_TX_RX);
> +			tcmr |=	  SSC_BF(TCMR_START, fs_edge);
> +		} else if (ssc->lrclk_from_rf_pin) {
> +			/* assume RF is to be used when RK is used as BCLK input */

This comment is not longer true...

> +			/* Note: won't work correctly on SAMA5D2 due to errata */
> +			rcmr |=	  SSC_BF(RCMR_START, fs_edge);
> +			tcmr |=	  SSC_BF(TCMR_START, SSC_START_TX_RX);
> +		} else {
> +			rcmr |=	  SSC_BF(RCMR_START, fs_edge);
> +			tcmr |=	  SSC_BF(TCMR_START, fs_edge);
> +		}
> +	}
>   
>   	if (atmel_ssc_cbs(ssc_p)) {
>   		/*
> 

Thanks and best regards,
Codrin