linux-kernel - Re: [PATCH v3] rtc: s3c: Don't print an error on probe deferral

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Date:	Tue, 15 Mar 2016 10:50:15 +0900
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Javier Martinez Canillas <javier@....samsung.com>,
	linux-kernel@...r.kernel.org
Cc:	Joe Perches <joe@...ches.com>,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	linux-samsung-soc@...r.kernel.org, rtc-linux@...glegroups.com
Subject: Re: [PATCH v3] rtc: s3c: Don't print an error on probe deferral

On 15.03.2016 10:38, Javier Martinez Canillas wrote:
> The clock and source clock looked up by the driver may not be available
> just because the clock controller driver was not probed yet so printing
> an error in this case is not correct and only adds confusion to users.
> 
> However, knowing that a driver's probe was deferred may be useful so it
> can be printed as a debug information.
> 
> Signed-off-by: Javier Martinez Canillas <javier@....samsung.com>
> 
> ---
> 
> Changes in v3:
> - Change debug messages again as suggested by Joe Perches.
> 
> Changes in v2:
> - Improve debug messages as suggested by Joe Perches.
> 
>  drivers/rtc/rtc-s3c.c | 19 ++++++++++++++-----
>  1 file changed, 14 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/rtc/rtc-s3c.c b/drivers/rtc/rtc-s3c.c
> index ffb860d18701..d01ad7e8078e 100644
> --- a/drivers/rtc/rtc-s3c.c
> +++ b/drivers/rtc/rtc-s3c.c
> @@ -501,18 +501,27 @@ static int s3c_rtc_probe(struct platform_device *pdev)
>  
>  	info->rtc_clk = devm_clk_get(&pdev->dev, "rtc");
>  	if (IS_ERR(info->rtc_clk)) {
> -		dev_err(&pdev->dev, "failed to find rtc clock\n");
> -		return PTR_ERR(info->rtc_clk);
> +		ret = PTR_ERR(info->rtc_clk);
> +		if (ret != -EPROBE_DEFER)
> +			dev_err(&pdev->dev, "failed to find rtc clock\n");
> +		else
> +			dev_dbg(&pdev->dev, "probe deferred due to missing rtc clk\n");
> +		return ret;
>  	}
>  	clk_prepare_enable(info->rtc_clk);
>  
>  	if (info->data->needs_src_clk) {
>  		info->rtc_src_clk = devm_clk_get(&pdev->dev, "rtc_src");
>  		if (IS_ERR(info->rtc_src_clk)) {
> -			dev_err(&pdev->dev,
> -				"failed to find rtc source clock\n");
> +			ret = PTR_ERR(info->rtc_src_clk);
> +			if (ret != -EPROBE_DEFER)
> +				dev_err(&pdev->dev,
> +					"failed to find rtc source clock\n");
> +			else
> +				dev_dbg(&pdev->dev,
> +					"probe deferred due to missing rtc src clk\n");
>  			clk_disable_unprepare(info->rtc_clk);
> -			return PTR_ERR(info->rtc_src_clk);
> +			return ret;
>  		}
>  		clk_prepare_enable(info->rtc_src_clk);
>  	}
> 

The error path starts looking complicated. This has now 4 indentation
levels...

I agree for removal of error in case of probe deferral because it might
be misleading but I don't see much benefit of a debug message.

Best regards,
Krzysztof