linux-kernel - Re: pwm: atmel: problem when disable pwm

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20140604144639.GI28484@ulmo>
Date:	Wed, 4 Jun 2014 16:46:39 +0200
From:	Thierry Reding <thierry.reding@...il.com>
To:	Raphaël Poggi <poggi.raph@...il.com>
Cc:	linux-kernel@...r.kernel.org, linux-pwm@...r.kernel.org
Subject: Re: pwm: atmel: problem when disable pwm

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

Content of type "application/pgp-signature" skipped