linux-kernel - Re: [PATCH] pwm: atmel: Fix disabling of PWM channels

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Date:	Thu, 9 Jun 2016 18:36:31 +0200
From:	Guillermo Rodriguez Garcia <guille.rodriguez@...il.com>
To:	Thierry Reding <thierry.reding@...il.com>,
	linux-kernel@...r.kernel.org, linux-pwm@...r.kernel.org,
	Nicolas Ferre <nicolas.ferre@...el.com>
Cc:	Guillermo Rodriguez <guille.rodriguez@...il.com>
Subject: Re: [PATCH] pwm: atmel: Fix disabling of PWM channels

Hello,

Any comments on this patch?

Guillermo

2016-05-13 13:09 GMT+02:00 Guillermo Rodriguez <guille.rodriguez@...il.com>:
> When disabling a PWM channel, the PWM clock was being stopped
> immediately after writing to PWM_DIS. As a result, the disabling
> of the PWM channel did not complete properly, and the PWM output
> might be left at the wrong level.
>
> Fix this by waiting for the channel to be effectively disabled
> (by checking the PWM_SR register) before disabling the clock.
>
> Signed-off-by: Guillermo Rodriguez <guille.rodriguez@...il.com>
> ---
>  drivers/pwm/pwm-atmel.c |   10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/drivers/pwm/pwm-atmel.c b/drivers/pwm/pwm-atmel.c
> index 0e4bd4e..a714434 100644
> --- a/drivers/pwm/pwm-atmel.c
> +++ b/drivers/pwm/pwm-atmel.c
> @@ -271,6 +271,16 @@ static void atmel_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
>         mutex_unlock(&atmel_pwm->isr_lock);
>         atmel_pwm_writel(atmel_pwm, PWM_DIS, 1 << pwm->hwpwm);
>
> +       /*
> +        * Wait for the PWM channel disable operation to be effective before
> +        * stopping the clock.
> +        */
> +       timeout = jiffies + 2 * HZ;
> +       while ((atmel_pwm_readl(atmel_pwm, PWM_SR)& (1 << pwm->hwpwm)) &&
> +              time_before(jiffies, timeout)) {
> +               usleep_range(10, 100);
> +       }
> +
>         clk_disable(atmel_pwm->clk);
>  }
>
> --
> 1.7.9.5
>



-- 
Guillermo Rodriguez Garcia
guille.rodriguez@...il.com