Subject: Re: [PATCH V3] ASoC: fsl_ssi: refine ipg clock usage in this module

From: Markus Pargmann <[email-masked]>
Date: Mon, 15 Sep 2014 12:05:41 +0200

On Fri, Sep 12, 2014 at 06:35:15PM +0800, Shengjiu Wang wrote:
> Check if ipg clock is in clock-names property, then we can move the
> ipg clock enable and disable operation to startup and shutdown, that
> is only enable ipg clock when ssi is working and keep clock is disabled
> when ssi is in idle.
> But when the checking is failed, remain the clock control as before.
> 
> Signed-off-by: Shengjiu Wang <[email-masked]>
> ---
> V3 change log:
> update patch according Nicolin and markus's comments
> 
> 
>  sound/soc/fsl/fsl_ssi.c |   53 ++++++++++++++++++++++++++++++++++++++++-------
>  1 file changed, 45 insertions(+), 8 deletions(-)
> 
> diff --git a/sound/soc/fsl/fsl_ssi.c b/sound/soc/fsl/fsl_ssi.c
> index 2fc3e66..6d1dfd5 100644
> --- a/sound/soc/fsl/fsl_ssi.c
> +++ b/sound/soc/fsl/fsl_ssi.c
> @@ -169,6 +169,7 @@ struct fsl_ssi_private {
>  	u8 i2s_mode;
>  	bool use_dma;
>  	bool use_dual_fifo;
> +	bool has_ipg_clk_name;
>  	unsigned int fifo_depth;
>  	struct fsl_ssi_rxtx_reg_val rxtx_reg_val;
>  
> @@ -530,6 +531,11 @@ static int fsl_ssi_startup(struct snd_pcm_substream *substream,
>  	struct snd_soc_pcm_runtime *rtd = substream->private_data;
>  	struct fsl_ssi_private *ssi_private =
>  		snd_soc_dai_get_drvdata(rtd->cpu_dai);
> +	int ret;
> +
> +	ret = clk_prepare_enable(ssi_private->clk);
> +	if (ret)
> +		return ret;
>  
>  	/* When using dual fifo mode, it is safer to ensure an even period
>  	 * size. If appearing to an odd number while DMA always starts its
> @@ -544,6 +550,21 @@ static int fsl_ssi_startup(struct snd_pcm_substream *substream,
>  }
>  
>  /**
> + * fsl_ssi_shutdown: shutdown the SSI
> + *
> + */
> +static void fsl_ssi_shutdown(struct snd_pcm_substream *substream,
> +                             struct snd_soc_dai *dai)
> +{
> +	struct snd_soc_pcm_runtime *rtd = substream->private_data;
> +	struct fsl_ssi_private *ssi_private =
> +		snd_soc_dai_get_drvdata(rtd->cpu_dai);
> +
> +	clk_disable_unprepare(ssi_private->clk);
> +
> +}
> +
> +/**
>   * fsl_ssi_set_bclk - configure Digital Audio Interface bit clock
>   *
>   * Note: This function can be only called when using SSI as DAI master
> @@ -1043,6 +1064,7 @@ static int fsl_ssi_dai_probe(struct snd_soc_dai *dai)
>  
>  static const struct snd_soc_dai_ops fsl_ssi_dai_ops = {
>  	.startup	= fsl_ssi_startup,
> +	.shutdown       = fsl_ssi_shutdown,
>  	.hw_params	= fsl_ssi_hw_params,
>  	.hw_free	= fsl_ssi_hw_free,
>  	.set_fmt	= fsl_ssi_set_dai_fmt,
> @@ -1168,17 +1190,22 @@ static int fsl_ssi_imx_probe(struct platform_device *pdev,
>  	u32 dmas[4];
>  	int ret;
>  
> -	ssi_private->clk = devm_clk_get(&pdev->dev, NULL);
> +	if (ssi_private->has_ipg_clk_name)
> +		ssi_private->clk = devm_clk_get(&pdev->dev, "ipg");
> +	else
> +		ssi_private->clk = devm_clk_get(&pdev->dev, NULL);
>  	if (IS_ERR(ssi_private->clk)) {
>  		ret = PTR_ERR(ssi_private->clk);
>  		dev_err(&pdev->dev, "could not get clock: %d\n", ret);
>  		return ret;
>  	}
>  
> -	ret = clk_prepare_enable(ssi_private->clk);
> -	if (ret) {
> -		dev_err(&pdev->dev, "clk_prepare_enable failed: %d\n", ret);
> -		return ret;
> +	if (!ssi_private->has_ipg_clk_name) {
> +		ret = clk_prepare_enable(ssi_private->clk);
> +		if (ret) {
> +			dev_err(&pdev->dev, "clk_prepare_enable failed: %d\n", ret);
> +			return ret;
> +		}
>  	}
>  
>  	/* For those SLAVE implementations, we ingore non-baudclk cases
> @@ -1236,8 +1263,9 @@ static int fsl_ssi_imx_probe(struct platform_device *pdev,
>  	return 0;
>  
>  error_pcm:
> -	clk_disable_unprepare(ssi_private->clk);
>  
> +	if (!ssi_private->has_ipg_clk_name)
> +		clk_disable_unprepare(ssi_private->clk);
>  	return ret;
>  }
>  
> @@ -1246,7 +1274,8 @@ static void fsl_ssi_imx_clean(struct platform_device *pdev,
>  {
>  	if (!ssi_private->use_dma)
>  		imx_pcm_fiq_exit(pdev);
> -	clk_disable_unprepare(ssi_private->clk);
> +	if (!ssi_private->has_ipg_clk_name)
> +		clk_disable_unprepare(ssi_private->clk);
>  }
>  
>  static int fsl_ssi_probe(struct platform_device *pdev)
> @@ -1321,8 +1350,16 @@ static int fsl_ssi_probe(struct platform_device *pdev)
>  		return -ENOMEM;
>  	}
>  
> -	ssi_private->regs = devm_regmap_init_mmio(&pdev->dev, iomem,
> +	ret = of_property_match_string(np, "clock-names", "ipg");
> +	if (ret < 0) {
> +		ssi_private->has_ipg_clk_name = false;
> +		ssi_private->regs = devm_regmap_init_mmio(&pdev->dev, iomem,
>  			&fsl_ssi_regconfig);

Sorry if I was unclear about that. My suggestion was to enable the clock
right here:
		clk_prepare_enable(ssi_private->clk);

Then you can remove ssi_private->has_ipg_clk_name and all
clk_prepare_enable() and clk_disable_unprepare() from above. Also you
can move the devm_clk_get() into this block.

It seems you really want to implement this for devicetrees where the
"ipg" clock-name is missing, but I don't understand why? I really can't
see any benefit of adding all these clk_prepare_enable() calls for all
cornercases that may occure. For example the clocks for AC97 are still
missing in this version.

Best regards,

Markus

> +	} else {
> +		ssi_private->has_ipg_clk_name = true;
> +		ssi_private->regs = devm_regmap_init_mmio_clk(&pdev->dev,
> +			"ipg", iomem, &fsl_ssi_regconfig);
> +	}
>  	if (IS_ERR(ssi_private->regs)) {
>  		dev_err(&pdev->dev, "Failed to init register map\n");
>  		return PTR_ERR(ssi_private->regs);
> -- 
> 1.7.9.5
> 
> 

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