[REGRESSION] amdgpu: thinkpad e495 backlight brightness resets after suspend

[Alex Deucher]

On Mon, Dec 23, 2024 at 4:08 AM Siva Mahadevan <me at svmhdvn.name> wrote:
>
> #regzbot introduced: 99a02eab8
>
> Observed behaviour:
> linux-stable v6.12.5 has a regression on my thinkpad e495 where
> suspend/resume of the laptop results in my backlight brightness settings
> to be reset to some very high value. After resume, I'm able to increase
> brightness further until max brightness, but I'm not able to decrease it
> anymore.
>
> Behaviour prior to regression:
> linux-stable v6.12.4 correctly maintains the same brightness setting on
> the backlight that was set prior to suspend/resume.
>
> Notes:
> I bisected this issue between v6.12.4 and v6.12.5 to commit 99a02eab8
> titled "drm/amdgpu: rework resume handling for display (v2)".

Odd.  That commit shouldn't affect the backlight per se.

>
> Hardware:
> * lenovo thinkpad e495
> * AMD Ryzen 5 3500U with Radeon Vega Mobile Gfx
> * VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI]
>   Picasso/Raven 2 [Radeon Vega Series / Radeon Vega Mobile Series]
>   (rev c2)

Please file a ticket here:
https://gitlab.freedesktop.org/drm/amd/-/issues
and attach your full dmesg output and we'll take a look.

Thanks,

Alex