Comment 0 for bug 1934557

Backlight does not change. Neither with the keys, nor with the slider. Values in /sys/class/backlight/amdgpu_bl0/brightness do change. However without effect on the actual brightness of the screen, which seems to be stuck at maximum brightness.

Following the instructions from here: https://wiki.ubuntu.com/Kernel/Debugging/Backlight

ProblemType: Bug
DistroRelease: Ubuntu 21.04
Package: linux-image-5.11.0-22-generic 5.11.0-22.23
ProcVersionSignature: Ubuntu 5.11.0-22.23-generic 5.11.21
Uname: Linux 5.11.0-22-generic x86_64
ApportVersion: 2.20.11-0ubuntu65.1
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC2: simon 1886 F.... pulseaudio
 /dev/snd/pcmC2D0p: simon 1886 F...m pulseaudio
 /dev/snd/controlC1: simon 1886 F.... pulseaudio
 /dev/snd/controlC0: simon 1886 F.... pulseaudio
CasperMD5CheckResult: pass
CurrentDesktop: ubuntu:GNOME
Date: Sat Jul 3 09:46:53 2021
InstallationDate: Installed on 2021-07-03 (0 days ago)
InstallationMedia: Ubuntu 21.04 "Hirsute Hippo" - Release amd64 (20210420)
MachineType: LENOVO 21A0CTO1WW
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
ProcFB: 0 amdgpudrmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-5.11.0-22-generic root=/dev/mapper/vgubuntu-root ro quiet splash vt.handoff=7
RelatedPackageVersions:
 linux-restricted-modules-5.11.0-22-generic N/A
 linux-backports-modules-5.11.0-22-generic N/A
 linux-firmware 1.197.1
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 04/23/2021
dmi.bios.release: 1.5
dmi.bios.vendor: LENOVO
dmi.bios.version: R1MET35W (1.05 )
dmi.board.asset.tag: Not Available
dmi.board.name: 21A0CTO1WW
dmi.board.vendor: LENOVO
dmi.board.version: Not Defined
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: None
dmi.ec.firmware.release: 1.5
dmi.modalias: dmi:bvnLENOVO:bvrR1MET35W(1.05):bd04/23/2021:br1.5:efr1.5:svnLENOVO:pn21A0CTO1WW:pvrThinkPadP14sGen2a:rvnLENOVO:rn21A0CTO1WW:rvrNotDefined:cvnLENOVO:ct10:cvrNone:
dmi.product.family: ThinkPad P14s Gen 2a
dmi.product.name: 21A0CTO1WW
dmi.product.sku: LENOVO_MT_21A0_BU_Think_FM_ThinkPad P14s Gen 2a
dmi.product.version: ThinkPad P14s Gen 2a
dmi.sys.vendor: LENOVO