Since updating to kernel v4.4.4 (from v4.4.3), I get vertical jitter on my display with almost every boot. The picture moves up and down with black horizontal stripes. This makes the system pretty much unusable.
I bisected it to the following commit:
drm/radeon/pm: adjust display configuration after powerstate
I am now running v4.4.4 with this commit reverted and so far so good. My hardware:
01:00.0 VGA compatible controller : Advanced Micro Devices, Inc. [AMD/ATI] Turks XT [Radeon HD 6670/7670] [1002:6758] (Sapphire HD 6670)
Kernel v4.5-rc7 is affected too.
I'll just revert it for now. Sorry for the breakage.
OK, thanks Alex.