Arch Linux

Megarock90

Member

Registered: 2012-01-18

Posts: 66

[FIXED] Backlight brightness broken at 100% (AMDGPU, radeon 680m igpu)

Today all of a sudden my backlight decided to malfunction when getting to max brightness.
It works correctly up to 95%, if I go 1 step further it gets completely dim, lower than 0%.
I didnt change anything nor have any clue why this began happening now. There werent any driver updates or anything recently, right?

running

cat /sys/class/backlight/amdgpu_bl1/(...)

on the brightness values returns the following values as so:
"actual_brightness":
at 95%, 63331
at 100%, 0
at 0%, 3084
"max_brightness": 65535

Happening on both 7.1.8 and 6.18.43 lts kernels. Running kde plasma, system up to date.

Last edited by Megarock90 (2026-08-12 23:19:10)

seth

Member

From: Won't reply 2 private help req

Registered: 2012-09-03

Posts: 77,415

Re: [FIXED] Backlight brightness broken at 100% (AMDGPU, radeon 680m igpu)

https://bbs.archlinux.org/viewtopic.php?id=314522
Seems it *was* fixed and now got re-introduced? And the wiki paragraph likely needs to be restored…

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Megarock90

Member

Registered: 2012-01-18

Posts: 66

Re: [FIXED] Backlight brightness broken at 100% (AMDGPU, radeon 680m igpu)

Confirming that adding  "amdgpu.dcdebugmask=0x40000" to my boot fixed it.

seth

Member

From: Won't reply 2 private help req

Registered: 2012-09-03

Posts: 77,415

Re: [FIXED] Backlight brightness broken at 100% (AMDGPU, radeon 680m igpu)

https://gitlab.freedesktop.org/drm/amd/ … items/5562
https://github.com/torvalds/linux/commi … 7999055566

d'ohh
Probably not necessary to restore the wiki assuming the fix is on the way.

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How to upload text · How to boot w/o GUI · Disable Windows Fast-Start! · Fix your xinitrc