https://bugs.freedesktop.org/show_bug.cgi?id=106529
--- Comment #3 from Mariusz Mazur mariusz.g.mazur@gmail.com --- dc=1 codepath has the problem occur 100% of the times the display wakes up (iirc).
dc=0 with your patch does not. It happens regularly, but not 100% of the times. Which I guess does indicate there's some timing issues involved.