pwm-led turns on during suspend

pwm-led turns on during suspend

[Fabio Estevam]

Hi,

On a imx6q-cubox-i board there is an LED controlled via pwm-leds and
it works as expected:

# cd /sys/class/leds/imx6\:red\:front/
# echo 248 > brightness  (LED is turned on with its maximum brightness)
# echo 0 > brightness (LED is turned off)

However after entering in suspend mode:

# echo enabled > /sys/class/tty/ttymxc0/power/wakeup
# echo mem > /sys/power/state

The LED is turned on with its maximum brightness.

Press a key in the console, system resumes and LED is turned off.

I would expect that the LED gets turned off in suspend, but this is
not happening.

Any ideas?

Thanks,

Fabio Estevam

Re: pwm-led turns on during suspend

[Russell King - ARM Linux]

On Fri, Nov 17, 2017 at 10:31:23AM -0200, Fabio Estevam wrote:
> Hi,
> 
> On a imx6q-cubox-i board there is an LED controlled via pwm-leds and
> it works as expected:
> 
> # cd /sys/class/leds/imx6\:red\:front/
> # echo 248 > brightness  (LED is turned on with its maximum brightness)
> # echo 0 > brightness (LED is turned off)
> 
> However after entering in suspend mode:
> 
> # echo enabled > /sys/class/tty/ttymxc0/power/wakeup
> # echo mem > /sys/power/state
> 
> The LED is turned on with its maximum brightness.
> 
> Press a key in the console, system resumes and LED is turned off.
> 
> I would expect that the LED gets turned off in suspend, but this is
> not happening.
> 
> Any ideas?

The LED is wired to the 3.3V supply, and most likely the PWM output goes
low when the SoC suspends.  As SolidRun boards don't have support for
powering down the board supplies, the 3.3V supply does not collapse on
suspend.

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 8.8Mbps down 630kbps up
According to speedtest.net: 8.21Mbps down 510kbps up

Re: pwm-led turns on during suspend

[Fabio Estevam]

Hi Russell,

On Fri, Nov 17, 2017 at 10:45 AM, Russell King - ARM Linux
<linux@armlinux.org.uk> wrote:

> The LED is wired to the 3.3V supply, and most likely the PWM output goes
> low when the SoC suspends.  As SolidRun boards don't have support for
> powering down the board supplies, the 3.3V supply does not collapse on
> suspend.

I managed to fix this by introducing pinctrl_pm_select_sleep_state()
support into drivers/leds/leds-pwm.c.

Here is the complete change:
https://pastebin.com/FCsLMuW1

Now I can get the LED to be turned off during suspend.

I will separate the changes and submit the patches.

Thanks