Backlight does not work on the legion 5 15arh

[Tanapoom Sermchaiwong]

Backlight keys/backlight control does not work. cat /sys/class/backlight/amdgpu_bl0/actual_brightness outputs

311

which is above the max brightness.

ProblemType: Bug
DistroRelease: Ubuntu 20.10
Package: linux-image-5.8.0-22-generic 5.8.0-22.23
ProcVersionSignature: Ubuntu 5.8.0-22.23-generic 5.8.14
Uname: Linux 5.8.0-22-generic x86_64
ApportVersion: 2.20.11-0ubuntu49
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC1: tanapoom 1505 F.... pulseaudio
 /dev/snd/controlC0: tanapoom 1505 F.... pulseaudio
CasperMD5CheckResult: skip
CurrentDesktop: ubuntu:GNOME
Date: Tue Oct 13 21:20:31 2020
InstallationDate: Installed on 2020-10-13 (0 days ago)
InstallationMedia: Ubuntu 20.10 "Groovy Gorilla" - Beta amd64 (20200930)
MachineType: LENOVO 82B5
ProcFB: 0 amdgpudrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-5.8.0-22-generic root=UUID=a967ce85-0dda-4707-871b-69cbcbcf0b4e ro quiet splash vt.handoff=7
RelatedPackageVersions:
 linux-restricted-modules-5.8.0-22-generic N/A
 linux-backports-modules-5.8.0-22-generic N/A
 linux-firmware 1.190
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 08/19/2020
dmi.bios.release: 1.26
dmi.bios.vendor: LENOVO
dmi.bios.version: EUCN26WW
dmi.board.asset.tag: NO Asset Tag
dmi.board.name: LNVNB161216
dmi.board.vendor: LENOVO
dmi.board.version: NO DPK
dmi.chassis.asset.tag: NO Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Lenovo Legion 5 15ARH05
dmi.ec.firmware.release: 1.26
dmi.modalias: dmi:bvnLENOVO:bvrEUCN26WW:bd08/19/2020:br1.26:efr1.26:svnLENOVO:pn82B5:pvrLenovoLegion515ARH05:rvnLENOVO:rnLNVNB161216:rvrNODPK:cvnLENOVO:ct10:cvrLenovoLegion515ARH05:
dmi.product.family: Legion 5 15ARH05
dmi.product.name: 82B5
dmi.product.sku: LENOVO_MT_82B5_BU_idea_FM_Legion 5 15ARH05
dmi.product.version: Lenovo Legion 5 15ARH05
dmi.sys.vendor: LENOVO

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This change was made by a bot.

[Alex Hung (alexhung)]

I don't think amdgpu's actual_brightness works in the first place.

Did you try any of the following kerenl parameters?

acpi_backlight= [HW,ACPI]
              acpi_backlight=vendor
              acpi_backlight=video
              If set to vendor, prefer vendor specific driver
              (e.g. thinkpad_acpi, sony_acpi, etc.) instead
              of the ACPI video.ko driver.

[Tanapoom (timidpigeon)]

I tried those parameters but there seems to be no difference. Brightness still stuck at max.

[Tanapoom (timidpigeon)]

Also, Kernel 5.6 mainline works perfectly until I force shutdown the laptop (hold power button) then it breaks and gets stuck at around 90% brightness.

[AaronMa (mapengyu)]

Could you blacklist "nouveau" or install nvidia-driver-450?

[Tanapoom (timidpigeon)]

Installed nvidia-driver-450 and no noticeable difference.

[AaronMa (mapengyu)]

Do you have Windows10 installed?
Reboot from windows10 to 5.8.0-22 kernel or 5.6 kernel, try again.

[Tanapoom (timidpigeon)]

Yes, I am booting off of an external SSD connected through USB 3.1 port with windows on the internal SSD. Rebooting directly from Windows 10 to 5.8.0-22 kernel has no effect on changing brightness.

[roselove (roselove)]

I do have the same bug here on Linux 5.8.18-1-MANJARO x86_64 20.2 Nibia, also this been discussed here :

https://www.reddit.com/r/archlinux/comments/ihtlzj/problem_with_screen_backlight_regulation_in/

I think my backlight keys were working before installing core/amd-ucode but I'm not sure.

Got Lenovo Legion 5-15ARH05 Type 82B5 here.

[Muhammad Usama Anjum (musamaanjum)]

I'm facing the same issue. The brightness control was working fine on Ubuntu 20.04 a while ago. It seems like some package or update has broken the brightness control which I'm unable to identify. Any suggestion of a fix will be really helpful.