(In reply to Alex Deucher from comment #21)
> Created attachment 123503 [details] [review] [review]
> possible fix
> 
> Does the attached patch help?

Sorry for taking some time to reply. I had to re-compile and re-install the
kernel (never done it before, so I had to look up how to do it under Fedora). 

Anyways, the patch does not seem to have fix the problem. It did, however,
point me to a possible cause of the problem. 

I've discovered that if I remove the laptop from the power source, leaving it
on battery, and then plug the power cord in again, I can start applications
using DRI_PRIME=1 and the GPU won't get stuck at 100% usage. If I don't force
this power state change (battery -- power cord), the GPU will get stuck at 100%
usage.

This is true for both the original kernel-4.4.8-300.fc23.x86_64 and the patched
version. Also, since I am running the session with radeon.dpm=1, the GPU is not
heating up and the fan is running at normal speed. 

If you need, I can upload the dmesg of these tests.
Again, hope this can help somehow.
Cheers,
Arthur