(In reply to Harry Wentland from comment #12)
> Can you try blacklisting amdgpu and try S3 again?

(Assuming you mean adding "module_blacklist=amdgpu" on the kernel command
line:)

Sure, here is what happenes:

kernel old = amd-staging-drm-next as of early October 2017
kernel new = amd-staging-drm-next as of this week

          amdgpu
kernel  blacklisted  symptom after S3 resume
--------------------------------------------------------
old         no       resumes fine every time
old        yes       no HDMI signal, but system runs otherwise
new         no       no HDMI signal, system crashes every time
new        yes       no HDMI signal, but system runs otherwise

> We've seen issues with S3 on 4.15 RCs outside of amdgpu where the system
> wouldn't come back from S3. It's fixed in more recent RCs (definitely
> 4.15-rc6 and newer) but the issue might still be there in
> amd-staging-drm-next.

Hmmm. Would "drm-next-4.16" include this fix?