linux-kernel - Re: [PATCH v2 3/7] ASoC: fsl_sai: Add support to enable multiple data lines

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Date:   Mon, 29 Jul 2019 13:21:54 -0700
From:   Nicolin Chen <nicoleotsuka@...il.com>
To:     Daniel Baluta <daniel.baluta@....com>
Cc:     broonie@...nel.org, l.stach@...gutronix.de, mihai.serban@...il.com,
        alsa-devel@...a-project.org, viorel.suman@....com,
        timur@...nel.org, shengjiu.wang@....com, angus@...ea.ca,
        tiwai@...e.com, linux-imx@....com, kernel@...gutronix.de,
        festevam@...il.com, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, robh@...nel.org
Subject: Re: [PATCH v2 3/7] ASoC: fsl_sai: Add support to enable multiple
 data lines

On Sun, Jul 28, 2019 at 10:24:25PM +0300, Daniel Baluta wrote:
> SAI supports up to 8 Rx/Tx data lines which can be enabled
> using TCE/RCE bits of TCR3/RCR3 registers.
> 
> Data lines to be enabled are read from DT fsl,dl-mask property.
> By default (if no DT entry is provided) only data line 0 is enabled.
> 
> Signed-off-by: Daniel Baluta <daniel.baluta@....com>
> ---
>  sound/soc/fsl/fsl_sai.c | 11 ++++++++++-
>  sound/soc/fsl/fsl_sai.h |  4 +++-
>  2 files changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/sound/soc/fsl/fsl_sai.c b/sound/soc/fsl/fsl_sai.c
> index 637b1d12a575..5e7cb7fd29f5 100644
> --- a/sound/soc/fsl/fsl_sai.c
> +++ b/sound/soc/fsl/fsl_sai.c
> @@ -601,7 +601,7 @@ static int fsl_sai_startup(struct snd_pcm_substream *substream,
>  
>  	regmap_update_bits(sai->regmap, FSL_SAI_xCR3(tx),
>  			   FSL_SAI_CR3_TRCE_MASK,
> -			   FSL_SAI_CR3_TRCE);
> +			   FSL_SAI_CR3_TRCE(sai->soc_data->dl_mask[tx]);
>  
>  	ret = snd_pcm_hw_constraint_list(substream->runtime, 0,
>  			SNDRV_PCM_HW_PARAM_RATE, &fsl_sai_rate_constraints);
> @@ -888,6 +888,15 @@ static int fsl_sai_probe(struct platform_device *pdev)
>  		}
>  	}
>  
> +	/*
> +	 * active data lines mask for TX/RX, defaults to 1 (only the first
> +	 * data line is enabled
> +	 */
> +	sai->dl_mask[RX] = 1;
> +	sai->dl_mask[TX] = 1;
> +	of_property_read_u32_index(np, "fsl,dl-mask", RX, &sai->dl_mask[RX]);
> +	of_property_read_u32_index(np, "fsl,dl-mask", TX, &sai->dl_mask[TX]);

Just curious what if we enable 8 data lines through DT bindings
while an audio file only has 1 or 2 channels. Will TRCE bits be
okay to stay with 8 data channels configurations? Btw, how does
DMA work for the data registers? ESAI has one entry at a fixed
address for all data channels while SAI seems to have different
data registers.