Comment # 11 on bug 1189762 from Joerg Roedel

(In reply to Dainius Masiliunas from comment #10)
> Created attachment 852078 [details]
> Screencap of earlycon=efifb output
> 
> I now tried with earlycon=efifb, and that gives output! It seems that it
> works correctly all the way until the earlycon gets disabled and the regular
> console gets enabled. I also tried with both earlycon=efifb and nomodeset,
> and the result is the same except that there is an extra warning that this
> means the graphics drivers will be disabled. So I guess this is in some way
> related to amdgpu, then?

If that works, how about 'earlyprintk=efi,keep'. Does that show the output
until the actual crash?