"drm/core: Do not preserve framebuffer on rmfb prevends display" breaks display resume after dpms suspend

[Johannes Hirte]

On my system the display doesn't come back after a dpms suspend with
X11. The display is powered off after the configured time, but to get it
powered on I need to switch to console (and back to X). It doesn't
happen on simple keyboard or mouse input. Also the brightness is on the
lowest level, independently what adjustment it was before suspend.
Bisecting pointed me to this commit:

f2d580b9a8149735cbc4b59c4a8df60173658140
drm/core: Do not preserve framebuffer on rmfb, v4.

and reverting it solves the problem for me.

System is ProBook 6450b from HP with integrated Intel graphics
(Ironlake). The  xf86-video-intel driver is configured with UXA
acceleration.


regards,
  Johannes