Created attachment 141112 [details]
.config

I uploaded my .config file - maybe something in your Kconfig flags makes this
happen - you can try and rebuild latest kernel from Alex's repository using my
.config and see if you don't experience this anymore. 
https://cgit.freedesktop.org/~agd5f/linux/log/?h=amd-staging-drm-next

Other than that, since you system hard hangs so you can't do any postmortem
dumps, you can at least provide output from events tracing though trace_pipe to
catch live logs on the fly. Maybe we can infer something from there...

So again - 
Load the system and before starting reproduce run the following trace command -

sudo trace-cmd start -e dma_fence -e gpu_scheduler -e amdgpu -v -e
"amdgpu:amdgpu_mm_rreg" -e "amdgpu:amdgpu_mm_wreg" -e "amdgpu:amdgpu_iv"

then cd /sys/kernel/debug/tracing && cat trace_pipe

When the problem happens just copy all the output from the terminal to a log
file. Make sure your terminal app has largest possible buffer to catch ALL the
output.