https://bugzilla.kernel.org/show_bug.cgi?id=201539
--- Comment #70 from mirh (mirh@protonmail.ch) --- So.. I was also testing this on my Sapphire R9 290 Tri-X OC. And it seems to work pretty good.
I noticed an oddity though. The first time I tried it, when I switched to manual fan control, every time I wrote something to pwm1 after one second the thing seemed to reset to the default speed. On subsequent reboots this didn't seem to happen anymore.