https://bugzilla.kernel.org/show_bug.cgi?id=75241
--- Comment #33 from Christian König deathsimple@vodafone.de --- (In reply to Benjamin Herrenschmidt from comment #30)
The combo is Radeon R9 290 (from Sapphire) and good old Apple Cinema Display 23" (1920x1200x60 fixed resolution display) on DVI.
Well this bug report is about nearly ten year old hardware and was fixed almost two years ago (we just forgot to close it).
So please open a separate bug report preferable in the FDO bugzilla.