https://bugs.kde.org/show_bug.cgi?id=460329
Bug ID: 460329
Summary: VRR flicker possibly caused due to vsync latency
Classification: Plasma
Product: kwin
Version: 5.25.5
Platform: Archlinux
OS: Linux
Status: REPORTED
Severity: normal
Priority: NOR
Component: core
Assignee: kwin-bugs-n...@kde.org
Reporter: djaz...@gmail.com
Target Milestone: ---
SUMMARY
When using KDE in X11 and Wayland with VRR enabled, RADV and an RX 6700 XT I
have been experiencing display flicker on my 144Hz monitor via DisplayPort and
HDMI. I am currently using GNOME 42.5 with the Mutter VRR patch, as this setup
allows for FreeSync with no flicker. As far as I've found, Plasma has vsync
forced on Wayland, which I believe may be making the issue visible due to added
latency. I am unsure if RADV adds latency with its vsync implementation, if
Kwin has higher latency than GNOME's Mutter, if Kwin's Wayland implementation
is not handing the desire for tearing by default for some users relying on
Freesync or if there's an issue with direct scanout.
My issue may be similar to Bug 450914 and Bug 450884. However, I am making this
bug report as from what I gather a tear-free experience is forced in Wayland by
default, which may be the issue. Also my refresh rate is not limited to 60. The
issue still persists in Halo when limiting to 120Hz in the game's settings and
when using DXVK Async while the issue does not occur in GNOME using VRR.
STEPS TO REPRODUCE
1. Enable VRR in display settings (also in config for X11).
2. Launch a game (tried with Halo: The Master Chief Collection (Proton) and
Terraria (Native)
OBSERVED RESULT
Flicker present from the start of playing a game, especially evident when
loading into a level in Halo and playing in general.
EXPECTED RESULT
A more stable presentation of frames on my display, which is achievable with
GNOME when using the Mutter VRR patch yet not possible for me using
Plasma/Kwin.
SOFTWARE/OS VERSIONS
OS: EndeavourOS Linux x86_64
Kernel: 5.19.13-zen1-1-zen
DE (non-issue for me): GNOME 42.5 (VRR patch using Wayland)
DE (issue visible): KDE 5.25.5 (X11 and Wayland)
Mesa: 22.1.7 (RADV)
Wayland: 1.21 with Kwayland Integration
GPU: RX 6700 XT
ADDITIONAL INFORMATION
I have commented on a bug report for Mesa that may be relevant. I feel the need
to do this as I am unsure where the issue is exactly coming from and if a
variety of issues may be making the issue I am having more visible.
https://gitlab.freedesktop.org/mesa/mesa/-/issues/6984
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