Arch Linux

Caspian

Member

Registered: 2007-05-22

Posts: 265

Plasma 5 backlight not being restored

I'm having issues with backilight in Plasma 5. I have Asus laptop with Intel graphics. I can change the backlight without issues, but when due to inactivity brightness gets lowered automatically or screen turns off the backlight doesn't restore to it's previous value when I move the mouse or press a key on keyboard (I need to bring the brightness up manually).

I'm using the this in my /etc/X11/xorg.conf.d/20-intel.conf :

Option      "Backlight"    "intel_backlight"

Any ideas or suggestions on what to try?

Last edited by Caspian (2015-12-18 10:27:10)

zamzing

Member

From: Washington, DC

Registered: 2015-10-08

Posts: 24

Re: Plasma 5 backlight not being restored

See if the fixes in Laptop/Asus can help.  This one jumped out at me:

all power options work just fine, only brightness control needs module asus-nb-wmi to be loaded and acpi_backlight=intel acpi_osi=

The last two are kernel options.

Caspian

Member

Registered: 2007-05-22

Posts: 265

Re: Plasma 5 backlight not being restored

@zamzing:

Thanks for this. I added the acpi_backlight=intel acpi_osi=Linux to my kernel options. We'll see if this helps. I'll report back

Caspian

Member

Registered: 2007-05-22

Posts: 265

Re: Plasma 5 backlight not being restored

Still experiencing the same behaviour after adding acpi_backlight=intel acpi_osi=Linux kernel options. It didn't help unfortunately

AnAkkk

Member

Registered: 2014-03-03

Posts: 148

Re: Plasma 5 backlight not being restored

@zamzing:

Thanks for this. I added the acpi_backlight=intel acpi_osi=Linux to my kernel options. We'll see if this helps. I'll report back

These kernel options are old and are not meant to be used with recent kernels. This is more up to date:
https://wiki.archlinux.org/index.php/Ba … ne_options

Caspian

Member

Registered: 2007-05-22

Posts: 265

Re: Plasma 5 backlight not being restored

@AnAkkk:
Thanks for that link. I tried with acpi_backlight=vendor yesterday but it didn't help. I switched to the native value now. Hopefully this will work.

Caspian

Member

Registered: 2007-05-22

Posts: 265

Re: Plasma 5 backlight not being restored

It seems that using acpi_backlight=native did the trick. The backlight now restores almost every time. By "almost every time" I mean that I had KDE frozen on two occasions, when the laptop screen turned off. When I came back to start using it it was unresponsive. I could move the mouse cursor but KDE wasn't responding to mouse clicks or keyboard shortcuts. I needed to go to console and restart sddm.
Any ideas on how to "debug" this? Which logs should I check once this happens?

Last edited by Caspian (2015-10-24 05:55:55)

Caspian

Member

Registered: 2007-05-22

Posts: 265

Re: Plasma 5 backlight not being restored

Finally solved this by using acpi_backlight=none kernel option. All others had some sort of issues. Thanks for the help everyone.

TicTac

Member

Registered: 2011-07-02

Posts: 11

Re: Plasma 5 backlight not being restored

I have the same problem on Toshiba laptop which I described here. I tried different acpi_backlight configs but none of them makes a difference. Did you add anything else in the bootloader?

Caspian

Member

Registered: 2007-05-22

Posts: 265

Re: Plasma 5 backlight not being restored

No, nothing that has anything to do with video/backlight. I just saw that you have AMD card, so it could be a completely different issue.

Caspian

Member

Registered: 2007-05-22

Posts: 265

Re: Plasma 5 backlight not being restored

I'm still having this very annoying issue. KDE doesn't restore backlight on my laptop screen after in gets turned off for power saving (it doesn't happen every time).
Tried different acpi_backlight kernel options (currently using none). I've masked systemd backlight service and have "intel_backlight" option in /etc/X11/xorg.conf.d/20-intel.conf (without this lowering of brightness due to inactivity doesn't even work).
Does anyone have any ideas or suggestions? I don't have these issues in gnome.