https://bugzilla.kernel.org/show_bug.cgi?id=98751
--- Comment #19 from Robin Bankhead kernel@headbank.co.uk --- (In reply to Alex Deucher from comment #10)
Created attachment 178001 [details] possible fix
Does the attached patch help?
Nope, just built 4.0.5-gentoo which has this patch applied, laptop LCD still goes dark when radeondrmfb takes over from simplefb (or around that point, when the display would normally flicker at the changeover).