Comment 20 for bug 849782

Ok, the important line is

[drm:g4x_update_wm], Setting FIFO watermarks - A: plane=2, cursor=2, B: plane=26, cursor=6, SR: plane=59, cursor=6

which means that your hardware did not inherit the broken Crestline silicon, and an actual FIFO underrun is much less likely. Might still be worth running with drm.debug=0x1 and keeping an eye out for FIFO underrun warnings. And as is the nature of such issues, a change in rendering patterns is also likely to provoke running into different memory constraints (so a FIFO underrun is susceptible to userspace changes).