[PATCH] drm/amd: Only allow one entity to control ABM

[Gergo Koteles]

Hi> 

> ABM will reduce the backlight and compensate by adjusting brightness and contrast of the image. It has 5 levels: 0, 1, 2, 3, 4. 0 means off. 4 means maximum backlight reduction. IMO, 1 and 2 look okay. 3 and 4 can be quite impactful, both to power and visual fidelity.

I tried this with 6.9 and it looks weird with an OLED panel used with
dark UI settings.
The dark is no longer dark, everything is brighter.
I turned this feature off with amdgpu.abmlevel=0.

Best regards,
Gergo