Comment # 2 on bug 69790 from Ville Syrjala

I managed to reproduce this on my HSW. But it seems that it's somehow random as
it doesn't happen every time. It's rather hard to reproduce actually when you
just retry the same mode w/ 'testdisplay -o'.

There's no difference in dmesg between a good and bad modesets using the same
mode.

As it stands, I don't have any good ideas as to what might be happening.