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

From: Tony Prisk
Date: Tue Oct 23 2012 - 23:48:35 EST


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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