explicit sync causes flickering in games on an Intel Arc A750 GPU

[feschber]

Please fill out the following:

• Sway Version:

  • swaymsg -t get_version or sway -v
    sway version 1.10-dev-77b9ddab (Aug 26 2024, branch 'master')

• Configuration File:

  • default config

• Description:

  • In game (Counter-Strike 2) there is severe flickering on an Intel Arc A750 system since explicit sync was added.
  • Reverting explicit sync support (05e895c) fixes this issue.

  Interestingly, the flickering does not occur in GNOME, which supposedly also supports explicit-sync, which leads me to believe this might not just be a GPU driver issue.

[kennylevinsen]

While this is most likely a GPU driver bug, it would be useful to have the debug log from a sway run producing the issue (it will tell us about direct scanout), as well as the mesa and kernel version.

At the same time, check if the issue reproduces with the Vulkan renderer (running sway with WLR_RENDERER=vulkan, rather than the gles2 default).

[feschber]

WLR_RENDERER=vulkan indeed works without any flickering!

Here is a log with gles2 producing the error and one with vulkan, where no flickering occurs.
Hope this helps!

sway-debug-log-gles2.log
sway-debug-log-vulkan.log

[kennylevinsen]

Your logs contain a very large number of tearing flip failures. Does the flickering happen with gles2 when tearing isn't enabled?

[feschber]

No, still flickering with tearing disabled.

[kanashimia]

I also had something similar happen on GTX 1050 Ti in other games, but it wasn't consistent and it is Nvidia anyway, probably a different issue.

Vulkan renderer only works because explicit sync support isn't merged yet for it.
You can set WLR_RENDER_NO_EXPLICIT_SYNC=1 to explicitly disable it for gles2 renderer.
With this patch: https://gitlab.freedesktop.org/wlroots/wlroots/-/merge_requests/4768 you should have same flickering problems happen on vulkan renderer too.