https://bugs.freedesktop.org/show_bug.cgi?id=106940
--- Comment #42 from SET nmset@netcourrier.com --- (In reply to Andrey Arapov from comment #41)
Not sure if that helps, but could you try reverting this commit? https://github.com/torvalds/linux/commit/ e03fd3f300f6184c1264186a4c815e93bf658abb
Reverted that commit, still a black screen with 4.19-rc4 in the above context. Using radeon for a useful laptop.