VRR in embedded breaks close to half screen frequency and bellow. fix attached

[adolfotregosa]

It seems to me that LFC (Low Framerate Compensation) or the doubling/tripling of the screen frequency isn't kicking in or close the middle of the panel frequency it breaks. I'm testing this on both an Asus Ally X and an OG Ally, and when limiting the framerate to 55 or 62 FPS, the issue becomes very noticeable during panning motion. If you toggle VRR (Variable Refresh Rate) off, the image stutters, as expected, since it's no longer synced with the screen frequency, but it's actually smoother than with VRR on. With VRR on, the image "jumps." As mentioned earlier, it seems like LFC or screen frequency doubling isn't working as expected. I can't be sure what exactly is malfunctioning because I can't directly monitor the screen's refresh rate. It could just as easily be an issue with how Gamescope is outputting frames.

I'm limiting the FPS using the Steam game launch option: mangohud MANGOHUD_CONFIG=fps_limit=55,no_display %command% mangohud MANGOHUD_CONFIG=fps_limit=62,no_display %command% But there are alternatives, like:

Libstrangle: strangle 55 %command% or strangle 62 %command% VKD3D: VKD3D_FRAME_RATE=55 %command% or VKD3D_FRAME_RATE=62 %command% DXVK: DXVK_FRAME_RATE=55 %command% or DXVK_FRAME_RATE=62 %command%

I've included a slow-motion recording to help demonstrate the issue @55FPS: https://youtu.be/NixcItH-D14. Skip to between 1 (VRR OFF) and 3 minutes (VRR ON), and you'll clearly see the poor frame pacing at the 3-minute mark (with VRR on). I turn VRR on around minute 2:10.

The patch that fixes this issue is attached revert-299bc34.zip

I also need to apply this patch so VRR toggle button appears for the ally and ally X. external_monitor.zip