[SteamOS 3.7] Backport fix for internal panel VRR toggle disappearing after disconnect/reconnect to an external VRR monitor

[matte-schwartz]

Your system information

• SteamOS version: SteamOS 3.7 / 20240919.1002
• Opted into Steam client beta?: Yes
• Opted into SteamOS beta?: Yes, SteamOS Main
• Have you checked for updates in Settings > System?: Yes

Please describe your issue in as much detail as possible:

As a part of testing my ROG Ally display configuration that was upstreamed into gamescope, I found a bug with the internal VRR display losing VRR capability in drm_info if it was docked to an external monitor that also supported VRR, had VRR enabled in gamescope-session, and then was undocked. I thought it might be a gamescope issue at first, but then I tested amd-staging-drm-next and found that it did not have the issue.

A fixed/broken bisect led me to: torvalds/linux@f91a9af as the resolving commit. The commit only made it into 6.12-rc1 and 6.11.x, but it applies cleanly against 6.8.12-valve3 so I built and tested on my ROG Ally to confirm it fixed the issue. Also tested on my Steam Deck OLED to confirm it didn't cause any unexpected regressions.

Let me know if there's a better forum to send or request backports like this as well. I have a few audio patches for the Ally X from upstream and lkml that I've rebased for frog/6.8 on linux-integration that might be good to get in the kernel, especially once the gamescope config work makes it into a tagged release on Main.