https://bugs.freedesktop.org/show_bug.cgi?id=84627
--- Comment #1 from smoki smoki00790@gmail.com --- OK bisected kernel fast, by lucky guessing :) So for the kernel it is:
02376d8282b88f07d0716da6155094c8760b1a13
drm/radeon: Allow write-combined CPU mappings of BOs in GTT (v2) v2: fix rebase onto drm-fixes