Stalls in display- and window updates with kernel 6.8.4

[eselarm]

I upgraded from my own-compiled Armbian kernel 6.8.0-rc5 to 6.8.4 and there are now very annoying stall when for example I drag a KDE Konsole window.

Also when I play a 1080p50 HEVC video, as  son as a move the mouse, the whole video stalls.

 

Besides 6.8.0-rc5, the normal apt provide 6.8.1-edge-rockchip-rk3588 also works OK.  6.8.5 has the same issue as 6.8.4.

As indicated, I use KDE, X11, compositor disabled. Enabled makes no difference. OS base is Armbian Bookworm, but I have also used kernels 6.8.1 and 6.8.4 with a rootfs copied from an RaspberryPiOS and Opensuse-Tumbleweed. RPiOs is also Debian Bookworm, Tumbleweed is latest, KDE6. So it is not KDE6. KDE Wayland leaves black screen still (doesn't work), but that is not a showstopper.

 

Is anyone else experiencing the same?

 

PS: I run mainline as the vendor kernel 6.1.43 fails on running KVM (some tag of the Cortex-A55 is unknown) so qemu-KVM don't work/start and running VMs is a key use-case I bought the NanoPi-R6C for.