linux-kernel - Re: [PATCH v2 1/3] ASoC: fsl_sai: Fix noise when using EDMA

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Date:   Mon, 16 Sep 2019 15:49:05 -0700
From:   Nicolin Chen <nicoleotsuka@...il.com>
To:     Daniel Baluta <daniel.baluta@....com>
Cc:     broonie@...nel.org, timur@...nel.org, Xiubo.Lee@...il.com,
        festevam@...il.com, lgirdwood@...il.com, perex@...ex.cz,
        tiwai@...e.com, alsa-devel@...a-project.org,
        linux-kernel@...r.kernel.org, Mihai Serban <mihai.serban@....com>
Subject: Re: [PATCH v2 1/3] ASoC: fsl_sai: Fix noise when using EDMA

On Fri, Sep 13, 2019 at 10:28:05PM +0300, Daniel Baluta wrote:
> From: Mihai Serban <mihai.serban@....com>
> 
> EDMA requires the period size to be multiple of maxburst. Otherwise the
> remaining bytes are not transferred and thus noise is produced.
> 
> We can handle this issue by adding a constraint on
> SNDRV_PCM_HW_PARAM_PERIOD_SIZE to be multiple of tx/rx maxburst value.
> 
> Signed-off-by: Mihai Serban <mihai.serban@....com>
> Signed-off-by: Daniel Baluta <daniel.baluta@....com>

Acked-by: Nicolin Chen <nicoleotsuka@...il.com>

Thanks

> ---
> Changes since v1:
> * rename variable to use_edma as per Nicolin's suggestion.
> 
>  sound/soc/fsl/fsl_sai.c | 15 +++++++++++++++
>  sound/soc/fsl/fsl_sai.h |  1 +
>  2 files changed, 16 insertions(+)
> 
> diff --git a/sound/soc/fsl/fsl_sai.c b/sound/soc/fsl/fsl_sai.c
> index ef0b74693093..b517e4bc1b87 100644
> --- a/sound/soc/fsl/fsl_sai.c
> +++ b/sound/soc/fsl/fsl_sai.c
> @@ -628,6 +628,16 @@ static int fsl_sai_startup(struct snd_pcm_substream *substream,
>  			   FSL_SAI_CR3_TRCE_MASK,
>  			   FSL_SAI_CR3_TRCE);
>  
> +	/*
> +	 * EDMA controller needs period size to be a multiple of
> +	 * tx/rx maxburst
> +	 */
> +	if (sai->soc_data->use_edma)
> +		snd_pcm_hw_constraint_step(substream->runtime, 0,
> +					   SNDRV_PCM_HW_PARAM_PERIOD_SIZE,
> +					   tx ? sai->dma_params_tx.maxburst :
> +					   sai->dma_params_rx.maxburst);
> +
>  	ret = snd_pcm_hw_constraint_list(substream->runtime, 0,
>  			SNDRV_PCM_HW_PARAM_RATE, &fsl_sai_rate_constraints);
>  
> @@ -1026,30 +1036,35 @@ static int fsl_sai_remove(struct platform_device *pdev)
>  
>  static const struct fsl_sai_soc_data fsl_sai_vf610_data = {
>  	.use_imx_pcm = false,
> +	.use_edma = false,
>  	.fifo_depth = 32,
>  	.reg_offset = 0,
>  };
>  
>  static const struct fsl_sai_soc_data fsl_sai_imx6sx_data = {
>  	.use_imx_pcm = true,
> +	.use_edma = false,
>  	.fifo_depth = 32,
>  	.reg_offset = 0,
>  };
>  
>  static const struct fsl_sai_soc_data fsl_sai_imx7ulp_data = {
>  	.use_imx_pcm = true,
> +	.use_edma = false,
>  	.fifo_depth = 16,
>  	.reg_offset = 8,
>  };
>  
>  static const struct fsl_sai_soc_data fsl_sai_imx8mq_data = {
>  	.use_imx_pcm = true,
> +	.use_edma = false,
>  	.fifo_depth = 128,
>  	.reg_offset = 8,
>  };
>  
>  static const struct fsl_sai_soc_data fsl_sai_imx8qm_data = {
>  	.use_imx_pcm = true,
> +	.use_edma = true,
>  	.fifo_depth = 64,
>  	.reg_offset = 0,
>  };
> diff --git a/sound/soc/fsl/fsl_sai.h b/sound/soc/fsl/fsl_sai.h
> index b12cb578f6d0..76b15deea80c 100644
> --- a/sound/soc/fsl/fsl_sai.h
> +++ b/sound/soc/fsl/fsl_sai.h
> @@ -157,6 +157,7 @@
>  
>  struct fsl_sai_soc_data {
>  	bool use_imx_pcm;
> +	bool use_edma;
>  	unsigned int fifo_depth;
>  	unsigned int reg_offset;
>  };
> -- 
> 2.17.1
>