linux-kernel - Re: [PATCH 3/3] pwm: pxa: Remove clk_enabled field from struct pxa_pwm

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Date:	Mon, 1 Apr 2013 15:32:05 +0800
From:	Axel Lin <axel.lin@...ics.com>
To:	Eric Miao <eric.y.miao@...il.com>
Cc:	Thierry Reding <thierry.reding@...onic-design.de>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] pwm: pxa: Remove clk_enabled field from struct pxa_pwm_chip

2013/4/1 Eric Miao <eric.y.miao@...il.com>:
> On Sun, Mar 31, 2013 at 11:04 PM, Axel Lin <axel.lin@...ics.com> wrote:
>> clk_enable/clk_disable maintain an enable_count, clk_prepare and clk_unprepare
>> also maintain a prepare_count. These APIs will do prepare/enable when the first
>> user calling these APIs, and do disable/unprepare when the corresponding counter
>> reach 0. Thus We don't need to maintain a clk_enabled counter here.
>
> The original intention is to keep a paired clk enable counter no matter
> how the user calls pwm_enable()/pwm_disable() in pair or not, if that's
> no longer the case.

We don't need to worry that case:
In pwm core, both pwm_enable() and pwm_disable() will always check
PWMF_ENABLED flag.


/**
 * pwm_enable() - start a PWM output toggling
 * @pwm: PWM device
 */
int pwm_enable(struct pwm_device *pwm)
{
        if (pwm && !test_and_set_bit(PWMF_ENABLED, &pwm->flags))
                return pwm->chip->ops->enable(pwm->chip, pwm);

        return pwm ? 0 : -EINVAL;
}
EXPORT_SYMBOL_GPL(pwm_enable);

/**
 * pwm_disable() - stop a PWM output toggling
 * @pwm: PWM device
 */
void pwm_disable(struct pwm_device *pwm)
{
        if (pwm && test_and_clear_bit(PWMF_ENABLED, &pwm->flags))
                pwm->chip->ops->disable(pwm->chip, pwm);
}
EXPORT_SYMBOL_GPL(pwm_disable);
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