https://bugs.freedesktop.org/show_bug.cgi?id=107213
--- Comment #7 from Shmerl shtetldik@gmail.com --- I'm waiting for kernel 4.19.x to see if it improves anything, since it apparently had some fix that looks related:
https://lists.freedesktop.org/archives/dri-devel/2018-August/185123.html
drm/amd/display: Fix Vega10 black screen after mode change