https://bugzilla.kernel.org/show_bug.cgi?id=201539
--- Comment #15 from danglingpointerexception@gmail.com (danglingpointerexception@gmail.com) --- @Rudolf - Have you tried my solution in the link I provided above? I'm on 5.1.6 mainline and have no issues whatsoever with R9-290X
@Alex Smith - I've got a liquid-cooled card so don't know if my solution solves your fan problem but try following my steps in the link.
@Steffen - Try my steps in the link mate, it may solve your problem. Alex Ducher himself gave me the tip on fixing it.