Re: [PATCH V4] PWM: Add SPEAr PWM chip driver support

Shiraz Hashim
2012-10-25T04:17:53Z

On Wed, Oct 24, 2012 at 07:51:37AM +0200, Thierry Reding wrote:
> On Mon, Oct 22, 2012 at 04:36:41PM +0530, Shiraz Hashim wrote:
> [...]
> > +struct spear_pwm_chip {
> > + void __iomem *mmio_base;
> > + struct clk *clk;
> > + struct pwm_chip chip;
>
> My editor shows a tab between pwm_chip and chip. This should really be a
> space.
>
> > + ret = pwmchip_add(&pc->chip);
> > + if (ret < 0) {
> > + dev_err(&pdev->dev, "pwmchip_add() failed: %d\n", ret);
> > + return ret;
> > + }
> > +
> > + ret = clk_prepare_enable(pc->clk);
> > + if (ret < 0)
> > + return pwmchip_remove(&pc->chip);
>
> I think in order to fix the potential race condition that Viresh
> mentioned we should move the clk_prepare_enable() before the
> pwmchip_add(), but don't forget to disable and unprepare the clock if
> pwmchip_add() fails.
>
> Actually, can't we make it a clk_prepare() only at this point and move
> the clk_enable() and clk_disable() into the if block below? In case the
> compatible value is not "st,spear1340-pwm" we don't need the clock
> enabled.
>
> > +
> > + if (of_device_is_compatible(np, "st,spear1340-pwm")) {
> > + /*
> > + * Following enables PWM chip, channels would still be
> > + * enabled individually through their control register
> > + */
> > + val = readl_relaxed(pc->mmio_base + PWMMCR);
> > + val |= PWMMCR_PWM_ENABLE;
> > + writel_relaxed(val, pc->mmio_base + PWMMCR);
> > +
>
> Oh, and a spurious newline here... =)
>
> > + }
> > +
> > + /* only disable the clk and leave it prepared */
> > + clk_disable(pc->clk);
>
> This can go into the if block to match the clk_enable().

All suggestions would be included in V5. I hope this would be the
last one :).

--
regards
Shiraz