[Milhouse]

here is the log file with the custom xorg.conf, same black screen

dmesg : http://sprunge.us/RKfS
xorg log : http://pastebin.com/1Wy0Bvf5

Hmmm... it's used the custom xorg config, but Xorg still refuses to load the amdgpu driver and is instead using the radeon driver (which doesn't support Polaris).