R9285 Tonga with current agd5f amd-staging-4.9 I am seeing the top few lines of
single DVI-D 1920x1080 monitor flicker when scrolling in eg, a maximised xterm,
browser also affected but less so.

Forcing clocks high fixes.

Bisect was a failure, I got as far as -

# good: [38eabe8ecaf5fed9e8122091b27b406563daa2ad] drm/amdgpu: add the HDP 4.0
register headers

# bad: [e2f744ea6cba6a2a7d938ec89def196a59dbdd2d] drm/amdgpu/gfx9: correct wptr
pointer value

IIRC said 40 something commits to go.

The next 20 or so are all skips because I got either build fails or startx
hangs.

Gave up with the intention of doing git reset --hard
e2f744ea6cba6a2a7d938ec89def196a59dbdd2d and going backwards, but as the
history after doing that was totally different from as seen from head I didn't
bother :-)