Brightness change is negligible or fixed. Archlinux. HP elitebook 645 14 inch G11

[jianghudao]

this question is seem with https://h30434.www3.hp.com/t5/Notebook-Video-Display-and-Touch/Brightness-change-is-negligible-or-fi...

By default the directory in /sys/class/backlight is amdgpu_bl1 and brightness is quite up, It will blind my eyes because it has 500nit.

Whether I use root to manually modify the /sys/class/backlight/acpi_video0/brightness file or use kde powerdevil to modify the brightness(In fact, they are all modifying this file),I can't change the screen brightness.

When kernel parameters acpi_backlight=video is passed, the directory is acpi_video0 and brightness is max, too. the values can range from 0-99 but has no affect, can't decrease brightness.

I ensure I am loaded the amdgpu Kernel Modules.

And I have tried append acpi_backlight=vendor amdgpu.backlight=0 to the existing parameters.It seem with acpi_backlight=none.There is no directory under /sys/class/backlight/.And kde's powerdevil do not display the brightness control bar.

I hope this problem can be solved soon, like I said before, my eyes are almost blinded by it

[jianghudao]

It seems is a bug for amd cpu:
https://gitlab.freedesktop.org/drm/amd/-/issues/3701
Rollback Linux kernel to LTS Can Solving the problem.