Same symptoms here after upgrading from Linux 5.1 to 5.2 on Dell Latitude 5495,
Ryzen Pro 2700U. Graphical corruption, and/or the GUI will stop responding.
Magic SysRq is needed to reboot the computer.

kernel log contains the following bits when this happens:

[   44.921571] [drm:amdgpu_job_timedout] *ERROR* ring gfx timeout, signaled
seq=1112, emitted seq=1115
[   44.921574] [drm:amdgpu_job_timedout] *ERROR* Process information: process X
pid 4477 thread X:cs0 pid 4587
[   44.921575] [drm] GPU recovery disabled.