* Re: pwm: atmel: problem when disable pwm
[not found] <CACqcpZDziJs7QUKVYwio=La5LyRzBd+xeeRW=dPFcPzw0Wrn5Q@mail.gmail.com>
@ 2014-06-04 14:46 ` Thierry Reding
0 siblings, 0 replies; only message in thread
From: Thierry Reding @ 2014-06-04 14:46 UTC (permalink / raw)
To: Raphaël Poggi; +Cc: linux-kernel, linux-pwm
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Adding in the linux-pwm mailing list.
On Wed, Jun 04, 2014 at 02:56:13PM +0200, Raphaël Poggi wrote:
> Hello,
>
> I'm using the pwm-atmel driver to control led, but i'm facing a problem.
>
> When writing "echo 0 > /sys/class/leds/d1/brightness" (to switch off
> the led) sometimes the led stayed active.
>
> After investigation I think this problem is due to this function:
>
> static void atmel_pwm_disable(struct pwm_chip *chip, struct pwm_device *pwm)
> {
> struct atmel_pwm_chip *atmel_pwm = to_atmel_pwm_chip(chip);
>
> atmel_pwm_writel(atmel_pwm, PWM_DIS, 1 << pwm->hwpwm);
>
> clk_disable(atmel_pwm->clk);
> }
>
> By disable the pwm channel, I think the duty cycle "0" has not been
> update, and the channel is disable and stayed in active state (high or
> low depending of polarity).
This sounds like a bug that could be fixed by this commit:
916030db4399 pwm: atmel: correct CDTY calculation
What version of the kernel are you seeing this problem with? The above
commit was first added in v3.15-rc1, so maybe try that or any later
version to see if that fixes it.
Thierry
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