Comment # 14 on bug 109001 from Alex Deucher

(In reply to Matt Garman from comment #13)
> If I set amdgpu.dc=0 on my Ryzen 5 2400g, the system hard-locks as soon as X
> starts (i.e. hard reset via physical power button required).

There is no non-DC code for raven, so if you set dc=0, the display hardware is
not initialized and no display features are exposed to the OS.  The GPU
basically a render only device in that case.