https://bugs.freedesktop.org/show_bug.cgi?id=111122
--- Comment #6 from Nicholas Kazlauskas nicholas.kazlauskas@amd.com --- (In reply to Brian Schott from comment #3)
I think that I'm seeing something related with my 2700u Inspiron 7375.
If I have compositing enabled in XFWM4, the system will immediately stop responding after logging in with LightDM. If the window manager compositing is disabled, I'm able to log in, but then there is graphical corruption.
With git bisect I traced the problem back to https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/ ?h=df8368be1382&id=df8368be1382b442384507a5147c89978cd60702
I can edit the source file, and by only changing the KMS_DRIVER_MINOR definition from 32 to 30, get the system working correctly with 5.2.0.
Your issue in particular is likely unrelated - it's an issue in userspace.
The bisected commit is the one that allowed xf86-video-amdgpu to start scanning out DCC compressed buffers that mesa produces, with the caveat that mesa needs a hook on present for the re-tile. My guess is that hook isn't running when you aren't using "compositing".
I'm not sure if mesa or xf86-video-amdgpu have options yet to disable DCC or not, but for that particular setup you'd probably want it disabled.