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:
Fnkeys show the brightness slider on the display moving.
/sys/class/backlight/amdgpu_bl0/brightnesschanges accordingly from 0 to 255.
- The display does not show any brightness change.
- Manually writing to
brightnessdoes not change the display's brightness either.
/sys/class/backlight/amdgpu_bl0/actual_brightnessstays 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-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
amdgpudrivers, 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
acpi_video0 acpi_video1 amdgpu_bl0
Other things that did not work:
acpi_osi=(hangs at boot)
- BIOS update (no other version available)
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?