[REGRESSION] Brightness at max level after waking up from sleep on AMD Laptop

[Filip Hejsek]

Hello,

On Sat, 2024-07-27 at 19:52 +0300, serg.partizan at gmail.com wrote:
> Hello,
> 
> After updating from 6.8.9 to 6.9.1 I noticed a bug on my HP Envy x360 
> with AMD Ryzen 5 4500U.
> 
> #regzbot introduced: v6.8.9..v6.9.1
> 
> After waking up from sleep brightness is set to max level, ignoring 
> previous value.

This issue is tracked here:
#regzbot link: https://gitlab.freedesktop.org/drm/amd/-/issues/3474


> With the help of Arch Linux team, we was able to track bad commit to 
> this: 
> https://gitlab.freedesktop.org/agd5f/linux/-/commit/63d0b87213a0ba241b3fcfba3fe7b0aed0cd1cc5
> 
> [...]

This commit does not introduce the bug, it only makes it possible to
set the ABM level without requiring support from the compositor. It's
very likely that the bug has existed for a long time, it just hasn't
surfaced because no compositor enabled the ABM power savings featue.
Now that power-profiles-daemon can enable it through sysfs, the bug has
been exposed.

So I think this actually might not be a regression, just a new feature
that exposed an old bug.

--
Filip