The AMD-Vi messages in the log look OK. I'm seeing the same on my Raven system
(Ryzen 5 2400G desktop).

I'm currently running a 4.19-rc1+ kernel from Alex Deucher's drm-next-4.20-wip
branch. I haven't tried rc3 from the master branch yet. I'll try it tonight and
see if I can reproduce the issue.