linux-kernel - Re: [PATCH] pwm: add spear pwm driver support

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Date:	Fri, 19 Oct 2012 12:23:08 +0530
From:	viresh kumar <viresh.kumar@...aro.org>
To:	Shiraz Hashim <shiraz.hashim@...com>
Cc:	thierry.reding@...onic-design.de,
	spear--sw-devel@...ts.codex.cro.st.com,
	linux-kernel@...r.kernel.org, spear-devel@...t.st.com
Subject: Re: [PATCH] pwm: add spear pwm driver support

On Fri, Oct 19, 2012 at 11:29 AM, Shiraz Hashim <shiraz.hashim@...com> wrote:
> On Thu, Oct 18, 2012 at 11:11:06PM +0530, viresh kumar wrote:
>> On Thu, Oct 18, 2012 at 4:58 PM, Shiraz Hashim <shiraz.hashim@...com> wrote:

>> > +static int __devexit spear_pwm_remove(struct platform_device *pdev)
>> > +{
>> > +       struct spear_pwm_chip *pc = platform_get_drvdata(pdev);
>> > +       int i;
>> > +
>> > +       if (WARN_ON(!pc))
>> > +               return -ENODEV;
>> > +
>> > +       for (i = 0; i < NUM_PWM; i++) {
>> > +               struct pwm_device *pwmd = &pc->chip.pwms[i];
>> > +
>> > +               if (!test_bit(PWMF_ENABLED, &pwmd->flags))

One point here: If i am not wrong you want to disable pwmd if it is enabled.
Shouldn't you check for if (test_bit(PWMF_ENABLED, &pwmd->flags)) instead?

>> > +                       if (clk_prepare_enable(pc->clk) < 0)
>> > +                               continue;
>> > +
>> > +               spear_pwm_writel(pc, i, PWMCR, 0);
>> > +               clk_disable_unprepare(pc->clk);
>> > +       }
>>
>> You are enabling/disabling clock N times here and each of these will
>> write to an register. Do something better.
>>
>
> I need to shut down all active pwms, how else would you suggest that ?

Sorry, i misread the code on the second go :(

I am proposing something like:

static int __devexit spear_pwm_remove(struct platform_device *pdev)
{
       struct spear_pwm_chip *pc = platform_get_drvdata(pdev);
       int i, clk_enabled = 0;

       if (WARN_ON(!pc))
               return -ENODEV;

       for (i = 0; i < NUM_PWM; i++) {
               struct pwm_device *pwmd = &pc->chip.pwms[i];

               if (!test_bit(PWMF_ENABLED, &pwmd->flags) && !clk_enabled)
                       if (clk_prepare_enable(pc->clk) < 0)
                               continue;
		       else
			       clk_enabled++;

               spear_pwm_writel(pc, i, PWMCR, 0);
       }

       if (clk_enabled)
	       clk_disable_unprepare(pc->clk);
       ...
}
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