(In reply to freedesktop from comment #27)
> OK there seems to be something screwy going on with the amdgpu.dpm option -
> if that's set to 0, it still results in a blank screen. It has to be removed
> entirely from the kernel command line for boot to work for me on 4.19.
> 
> I'm not sure if that's a different bug or not, but can anyone who had
> success with removing the option, also test with amdgpu.dpm=0 to see if it
> still results in a blank screen?
> 
> Also, are FD BZ email notifications broken for anyone else?

I can confirm that attempting to boot with either amdgpu.dpm=0 or amdgpu.dpm=1
results in the same black screen issue on my PC

I am now running Fedora 29 with kernel 4.19.5 (MSI R9 390 8GB Gaming GPU) and
the only way to boot is by completely removing the amdgpu.dpm kernel parameter.