This is a regression in 4.20.x, the same userspace works ok on 4.19.
I could bisect, but it's my main machine so I can't quite dedicate the time,
any hint would be appreciated.
The kernel is booted using iommu=soft. full iommu hangs on boot, and noimmu
disables the wi-fi.

Dmesg:
> [  702.207054] [drm:amdgpu_job_timedout [amdgpu]] *ERROR* ring gfx timeout, signaled seq=1340, emitted seq=1342
> [  702.207061] [drm] GPU recovery disabled.

lspci -nn:
05:00.0 VGA compatible controller [0300]: Advanced Micro Devices, Inc.
[AMD/ATI] Device [1002:15dd] (rev c4)

It's a thinkpad e485 laptop with:
AMD Ryzen 5 2500U with Radeon Vega Mobile Gfx (family: 0x17, model: 0x11,
stepping: 0x0)