https://bugzilla.kernel.org/show_bug.cgi?id=203439
Bug ID: 203439 Summary: amdgpu: [REG 4.20 -> 5.0] Brightness minimum level is too high Product: Drivers Version: 2.5 Kernel Version: 5.0 Hardware: All OS: Linux Tree: Mainline Status: NEW Severity: normal Priority: P1 Component: Video(DRI - non Intel) Assignee: drivers_video-dri@kernel-bugs.osdl.org Reporter: spaz16@wp.pl Regression: No
I have Huawei Matebook D 14 with AMD Ryzen 2500U.
Since kernel 5.0.x the minimum brightness level is too high. It is not possible to dim the display as much as on previous kernel version. Kernel 4.20 also allows to disable the backlight on level 0.
Value of "0" in "/sys/class/backlight/amdgpu_bl0/brightness" currently doesn't disable backlight as in previous version. Value of "1" means the screen is dim, but not as much as in kernel 4.20. Sometimes the screen is still too bright even on level 0 in kernel 5.0.
Since commit 206bbafe00dcacccf40e6f09e624329ec124201b I can see the define:
#define AMDGPU_DM_DEFAULT_MIN_BACKLIGHT 12
Maybe it should be defined to "0" to restore the old behavior? (I haven't tested yet)