I have been trying myself for the moment to get some info with just debug
parameters:

amdgpu.dc=1 
amdgpu.vm_fault_stop=2 
amdgpu.vm_debug=1 
amdgpu.gpu_recovery=0 

Incidentally I couldn't get any freeze to happen after running two troublesome
games for about two hours each (left idle but on load, Pillars of Eternity and
Surviving Mars) but this could mean anything as they happen completely
randomly. 

Perhaps someone who can reproduce the issue instantly can test the parameters
more reliably?