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The brightness (LCD backlight) controls on a Lenovo IdeaPad Gaming 3 (15ARH05, LCD display, AMD Renoir CPU Ryzen 5 4600H, discrete NVIDIA GeForce 1650 Ti Mobile) are not working:

  • Fn keys show the brightness slider on the display moving.
  • /sys/class/backlight/amdgpu_bl0/brightness changes accordingly from 0 to 255.
  • The display does not show any brightness change.
  • Manually writing to brightness does not change the display's brightness either.
  • /sys/class/backlight/amdgpu_bl0/actual_brightness stays at 311. I figure this indicates a problem with the amdgpu driver.
  • The display seems to stay at full brightness always.

Adjustments work fine on Windows 10. The laptop is running:

  • Kali Linux Rolling
  • linux-image-5.8.0-kali[23]-amd64 (based on 5.8.14) and custom-built kernels 5.9, 5.9.1 and 5.10-rc1, mostly based off the Kali config
  • X with amdgpu drivers, discrete graphics unused (proprietary NVIDIA drivers loaded and unloaded for testing).

I have tried booting with various acpi_backlight kernel options, which lead to various backlights being available in /sys/class/backlight/*/brightness:

  • acpi_backlight=video: acpi_video0 acpi_video1 amdgpu_bl0
  • acpi_backlight=vendor: amdgpu_bl0 ideapad
  • acpi_backlight=native: amdgpu_bl0
  • acpi_backlight=none: amdgpu_bl0

Other things that did not work:

  • acpi_osi=Linux (no change)
  • acpi_osi= (hangs at boot)
  • BIOS update (no other version available)
  • moving /lib/firmware/amdgpu/renoir_dmcu.bin away
  • patching amdgpu_dm.c

I am aware that there has been a number of updates related to backlights for AMDGPUs, like general support and fixes in kernel 5.7.x and updates to the scaling of brightness values >255 in 5.9, but so far this seems not to have helped my case (or possibly, broke more things). I am not looking for:

  • software alternatives
  • adjusting the gamma values
  • using discrete graphics (if it can be avoided)

What else can I do or look into to gain control of the backlight?

I came across this comment and this bug report, which seem to suggest that some kernel fixes may have broken other things. What would be the best place to report that?

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  • Hey! I have very similar machine (Legion 5 ARH05/ryzen4800h/1650TI), running ubuntu with mainline kernel 5.9.12 and have the same issue with backlight control, did you solved an issue?
    – ilov3
    Dec 20, 2020 at 20:00
  • Unfortunately I didn't so far (up to kernel 5.11.2 and BIOS FCCN16WW). It could be that it worked for a few versions of old kernels (somewhere maybe 5.6.x), which might be a starting point to locate how it broke and how to fix it again. Feb 27, 2021 at 20:56
  • Doesn't work in 5.7, didn't yet get custom 5.6.x to boot. Feb 28, 2021 at 18:24
  • 1
    Seems like they found a workaround, but I didn't tried it yet
    – ilov3
    Feb 28, 2021 at 21:43
  • I feel that the BIOS option might help you. Unfortunately, the Ideapad Gaming 3 does not offer GPU selection in BIOS (at least I could not find it), contrary to the Legion 5. I am going to try forcing caps->aux_support = false; in kernel driver code, though. Thanks for the link, I think I already went there once before the last answers came in. Mar 1, 2021 at 11:00

2 Answers 2

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Kernels 5.11.7, 5.12-rc3, and later allow the kernel parameter amdgpu.backlight=0 to be passed at boot to fix this issue for Lenovo IdeaPad Gaming 3, Lenovo Legion 5 and possibly other laptops.

For Debian-based distributions using GRUB the parameter can be added in /etc/default/grub:

GRUB_CMDLINE_LINUX="amdgpu.backlight=0"

After running update-grub and rebooting the backlight controls should work.

Previous kernels required patching: The workaround can be found in a GitLab issue. Forcing caps->aux_support = false; in drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c fixed the issue.

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  • Thanks! Solved my problem, too. Had the same issue with Thinkpad P14s AMD Gen2 and Ubuntu 21.04/Kernel 5.11. Aug 15, 2021 at 15:46
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I came across this thread trying to fix my own Fn keys.

My fix was going into BIOS setup and switching the Foolproof Fn Keys setting to [Disabled]. After saving the changes and restarting, everything is now working as smooth as butter. I hope this helps some of you as well!!

I'm using a Lenovo Yoga 6, but the feature should be on most Lenovo laptops

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