https://bugs.freedesktop.org/show_bug.cgi?id=106175
--- Comment #7 from Harry Wentland harry.wentland@amd.com --- Does your kernel tree have the following patches?
90fef6476917 Revert "drm/amd/display: disable CRTCs with NULL FB on their primary plane (V2)" c7bd22893408 Revert "drm/amd/display: fix dereferencing possible ERR_PTR()"
If not can you grab the latest drm-next-4.18-wip and check again? Those reverts should have fixed problems where mouse movement would slow the system down.