linux-kernel - Re: [PATCH] ASoC: Intel: kbl_rt5663_max98927: Simplify clk

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Date:   Mon, 8 Aug 2022 09:34:10 +0200
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Cezary Rojewski <cezary.rojewski@...el.com>,
        Liam Girdwood <liam.r.girdwood@...ux.intel.com>,
        Peter Ujfalusi <peter.ujfalusi@...ux.intel.com>,
        Bard Liao <yung-chuan.liao@...ux.intel.com>,
        Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>,
        Kai Vehmanen <kai.vehmanen@...ux.intel.com>,
        Mark Brown <broonie@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Harsha Priya <harshapriya.n@...el.com>,
        "Subhransu S. Prusty" <subhransu.s.prusty@...el.com>,
        Vinod Koul <vkoul@...nel.org>,
        Sriram Periyasamy <sriramx.periyasamy@...el.com>
Cc:     linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
        alsa-devel@...a-project.org
Subject: Re: [PATCH] ASoC: Intel: kbl_rt5663_max98927: Simplify clk_get()
 usage



On 8/7/22 22:18, Christophe JAILLET wrote:
> If clk_get() returns -ENOENT, there is no need to defer the driver, -ENOENT
> will be returned the same for each retries.
> So, return the error code directly instead of -EPROBE_DEFER.
> 
> Remove this special case and use dev_err_probe() to simplify code. It will
> also be less verbose if the clk is really deferred.
> 
> Fixes: f7f61e08fe58 ("ASoC: Intel: kbl: Enable mclk and ssp sclk early")
> Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> ---
> This is based on my understanding of clk_get().
> Review with care.
> 
> Not sure the Fixes tag is needed. The patch does not fix anything.
> If devm_clk_get() returns -ENOENT, it will just loop several time until
> the framework gives up.
> If it returns -EPROBE_DEFER, this case is already handled by the
> "return ret;"
> 
> So this patch should be a no-op, just a clean-up.

I can't pretend understanding the clk framework in depth, but the only
case where -ENOENT is returned seems to be this block in clk_hw_create_clk()

	if (!try_module_get(core->owner)) {
		free_clk(clk);
		return ERR_PTR(-ENOENT);
	}

I have no idea why this would be converted to a -EPROBE_DEFER. May to
account for module loading?

> ---
>  sound/soc/intel/boards/kbl_rt5663_max98927.c | 31 ++++----------------
>  1 file changed, 6 insertions(+), 25 deletions(-)
> 
> diff --git a/sound/soc/intel/boards/kbl_rt5663_max98927.c b/sound/soc/intel/boards/kbl_rt5663_max98927.c
> index 2d4224c5b152..07b00af2fa3c 100644
> --- a/sound/soc/intel/boards/kbl_rt5663_max98927.c
> +++ b/sound/soc/intel/boards/kbl_rt5663_max98927.c
> @@ -989,7 +989,6 @@ static int kabylake_audio_probe(struct platform_device *pdev)
>  {
>  	struct kbl_rt5663_private *ctx;
>  	struct snd_soc_acpi_mach *mach;
> -	int ret;
>  
>  	ctx = devm_kzalloc(&pdev->dev, sizeof(*ctx), GFP_KERNEL);
>  	if (!ctx)
> @@ -1009,32 +1008,14 @@ static int kabylake_audio_probe(struct platform_device *pdev)
>  			&constraints_dmic_2ch : &constraints_dmic_channels;
>  
>  	ctx->mclk = devm_clk_get(&pdev->dev, "ssp1_mclk");
> -	if (IS_ERR(ctx->mclk)) {
> -		ret = PTR_ERR(ctx->mclk);
> -		if (ret == -ENOENT) {
> -			dev_info(&pdev->dev,
> -				"Failed to get ssp1_sclk, defer probe\n");
> -			return -EPROBE_DEFER;
> -		}
> -
> -		dev_err(&pdev->dev, "Failed to get ssp1_mclk with err:%d\n",
> -								ret);
> -		return ret;
> -	}
> +	if (IS_ERR(ctx->mclk))
> +		return dev_err_probe(&pdev->dev, PTR_ERR(ctx->mclk),
> +				     "Failed to get ssp1_mclk\n");
>  
>  	ctx->sclk = devm_clk_get(&pdev->dev, "ssp1_sclk");
> -	if (IS_ERR(ctx->sclk)) {
> -		ret = PTR_ERR(ctx->sclk);
> -		if (ret == -ENOENT) {
> -			dev_info(&pdev->dev,
> -				"Failed to get ssp1_sclk, defer probe\n");
> -			return -EPROBE_DEFER;
> -		}
> -
> -		dev_err(&pdev->dev, "Failed to get ssp1_sclk with err:%d\n",
> -								ret);
> -		return ret;
> -	}
> +	if (IS_ERR(ctx->sclk))
> +		return dev_err_probe(&pdev->dev, PTR_ERR(ctx->sclk),
> +				     "Failed to get ssp1_sclk\n");
>  
>  	return devm_snd_soc_register_card(&pdev->dev, kabylake_audio_card);
>  }