[regression, bisected] Default pipe_split_policy MPC_SPLIT_AVOID causes flip_done timed out, blank screen on 3400G

The following crash happens consistently when I change Stellarium from full screen to windowed for the second time, i.e.

1. Boot afresh, log in under Wayland GNOME (haven't checked X11).
2. Start Stellarium full-screen.
3. Change to windowed mode.
4. Closed Stellarium.
5. Start Stellarium full-screen again.
6. Change to windowed mode.

At this point the screen goes black and messages like

[drm:drm_atomic_helper_wait_for_flip_done [drm_kms_helper]] *ERROR* [CRTC:62:crtc-0] flip_done timed out

are logged to dmesg. A reboot is required to restore normal operation.

Full dmesg log attached: fdto.txt

Observed with kernels 5.10.20 and 5.11.5. APU is Ryzen 5 3400G, connected to Samsung LU32H850UMUXEN on DisplayPort. Fedora 33, mesa-dri-drivers-20.3.4-2.fc33.x86_64.