linux-kernel - Re: [PATCH v3] pwm: vt8500: Update vt8500 PWM driver support

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Message-ID: <1351050535.23151.1.camel@gitbox>
Date:	Wed, 24 Oct 2012 16:48:55 +1300
From:	Tony Prisk <linux@...sktech.co.nz>
To:	Thierry Reding <thierry.reding@...onic-design.de>
Cc:	devicetree-discuss@...ts.ozlabs.org, arm@...nel.org,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3] pwm: vt8500: Update vt8500 PWM driver support

On Wed, 2012-10-24 at 00:14 +0200, Thierry Reding wrote:
> On Tue, Oct 23, 2012 at 07:10:24AM +1300, Tony Prisk wrote:
> [...]
> > @@ -87,6 +98,11 @@ static int vt8500_pwm_enable(struct pwm_chip *chip, struct pwm_device *pwm)
> >  {
> >  	struct vt8500_chip *vt8500 = to_vt8500_chip(chip);
> >  
> > +	if (!clk_enable(vt8500->clk)) {
> > +		dev_err(chip->dev, "failed to enable clock\n");
> > +		return -EBUSY;
> > +	};
> > +
> 
> I don't think that works. The clock API returns 0 on success and a
> negative error code on failure. So this should rather be something like:
> 
> 	err = clk_enable(vt8500->clk);
> 	if (err < 0) {
> 		dev_err(chip->dev, "failed to enable clock: %d\n", err);
> 		return err;
> 	}
> 
> > @@ -123,6 +153,12 @@ static int __devinit pwm_probe(struct platform_device *pdev)
> >  	chip->chip.ops = &vt8500_pwm_ops;
> >  	chip->chip.base = -1;
> >  	chip->chip.npwm = VT8500_NR_PWMS;
> > +	chip->clk = devm_clk_get(&pdev->dev, NULL);
> > +
> 
> The blank line should go above the call to devm_clk_get().
> 
> > +	if (IS_ERR_OR_NULL(chip->clk)) {
> > +		dev_err(&pdev->dev, "clock source not specified\n");
> > +		return PTR_ERR(chip->clk);
> > +	}
> [...]
> > +	if (!clk_prepare(chip->clk)) {
> > +		dev_err(&pdev->dev, "failed to prepare clock\n");
> > +		return -EBUSY;
> > +	}
> > +
> 
> Same comment here. I wonder how this code can work, since if the clock
> is properly prepared, then it will return 0, and the above will return
> -EBUSY.
> 
> >  	ret = pwmchip_add(&chip->chip);
> > -	if (ret < 0)
> > +	if (ret < 0) {
> > +		dev_err(&pdev->dev, "failed to add pwmchip\n");
> 
> Error messages can be considered prose, so this should be: "failed to
> add PWM chip".
> 
> Thierry

I don't know why none of this caused a failure when boot tested. The
clock should have been disabled 'automagically' at bootup, and never
reenabled. *shrug* Fixed in new patch v3 (didn't notice there was
already a v3).

Regards
Tony P

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