https://bugs.freedesktop.org/show_bug.cgi?id=93826
--- Comment #37 from Jan Niklas Hasse jhasse@gmail.com ---
Sorry, but I don't know what you mean by "using bitsect".
Changes to the source code of the driver are controlled via Git as commits. Assuming it once worked 144 Hz it's possible to use Git to find out which commit caused the flickering. This is done by identifying any commit which worked (good, in your case 4.4) and a commit which doesn't work (bad, 4.8). Bisecting will then help you find the first bad commit faster (by sectioning the pool of possible first bad commits in two sections repeatedly).
I'm not sure though that this good commit exists though. Flickering also happens with 4.4 for me.