Artifacts with radeonsi caused by DCC with pp_jimenezmlaa on RX 6700XT
The issue
Using Jimenez’s MLAA with OpenGL applications causes blocky rainbow-colored artifacts when DCC is enabled.
This happens on both Xorg and Wayland (I tested Plasma Wayland and Sway).
Steps to reproduce
Simply run something like pp_jimenezmlaa=16 glxgears
on an RX 6700XT.
The actual AA value (16 in this example) doesn't matter.
Running pp_jimenezmlaa_color
also exhibits the same symptoms.
Other 6000 series cards might also be affected. I also tried an old RX 550 but I could not reproduce this bug with it.
Workarounds
Setting AMD_DEBUG=nodisplaydcc works around the issue on Xorg.
On XWayland though, that variable crashes glxgears with "BadAlloc (insufficient resources for operation)". That might be caused by another bug but that's just speculation...
AMD_DEBUG=nodcc also works without crashing on Wayland although at a bigger performance cost.
Other clues
This bug is very similar to #5677 (closed) and might be related as it shares similar symptoms and the same workaround.
If these bugs are indeed related, DCC (on GFX10.3) is definitely the main culprit.
System information
- Mesa versions tested: git main branch (22), 21.3.3 (llvm13)
- OS: Kubuntu 20.04 LTS
- Kernels tested: 5.15.12-xanmod1, 5.11.0
- Xorg/XWayland: 1.20.13
- Wayland compositors tested: KDE, Sway
- X11 window managers tested: KWin, Openbox