[Milhouse]

@alxtr1bal: Include [pkg] patch: xf86-video-amdgpu: Latest commits (6a1ba04) adding Polaris 10 & 11 support (xf86-video-amdgpu) <- such commits are highly relevant for you.

Next time, please gather logfiles. Xorg.0.log and dmesg | pastebinit

With these we can file bugs at bugs.freedesktop.org so that this gets fixed. It won't happen magically.

Ok, last update not working :

Xorg log : http://sprunge.us/VcJK
dmesg : http://sprunge.us/XcBW

here's what i did to install :
First , installed the 7.90.005, with the processor GPU as primary.
Then , put the latest update in /Updates, change the primary video card as the RX 460, and boot.
Update is going ok, reboot, and then the Xorg won't start.

Not sure if this is the right way...

Thanks for the logs. It looks like the "ATI Radeon" driver is being loaded and not the updated "amdgpu" driver. Not sure how easy it is to work around that. Do you have two GPUs in your system, a Kaveri and Polaris? Can you disable the Kaveri?