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

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Message-ID: <1457984317.11972.123.camel@perches.com>
Date:	Mon, 14 Mar 2016 12:38:37 -0700
From:	Joe Perches <joe@...ches.com>
To:	Javier Martinez Canillas <javier@....samsung.com>,
	linux-kernel@...r.kernel.org
Cc:	Alexandre Belloni <alexandre.belloni@...e-electrons.com>,
	linux-samsung-soc@...r.kernel.org,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	rtc-linux@...glegroups.com
Subject: Re: [PATCH] rtc: s3c: Don't print an error on probe deferral

On Mon, 2016-03-14 at 16:31 -0300, Javier Martinez Canillas wrote:
> On 03/14/2016 04:11 PM, Joe Perches wrote:> > On Mon, 2016-03-14 at 16:05 -0300, 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 debug information.
> > []
> > > 
> > > diff --git 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 rtc clock\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 rtc source clock\n");
> > >  			clk_disable_unprepare(info->rtc_clk);
> > > -			return PTR_ERR(info->rtc_src_clk);
> > > +			return ret;
> > >  		}
> > >  		clk_prepare_enable(info->rtc_src_clk);
> > >  	}
> > Maybe the debug logging messages could be object->action like:
> > 
> > 	rtc clock probe deferred
> > 	rtc source clock probe deferred
> > 
> I found your suggested messages harder to read and more confusing. The
> action that happens is a probe function deferral and that is caused by
> a missing resource needed by the driver (clocks in this case).
> 
> But your messages seems to imply that the probe deferred action happens
> to a clock, it sounds like "rtc clock disabled" and that's not correct.

OK, then please change "due" to "due to" or "for" in your messages
because they make little sense now.