[Intel-gfx] black screen if sna & TearFree

[Grant]

> I'm using a Dell XPS 13 laptop on Gentoo and if I use:
>
> Option "AccelMethod" "sna"
> Option "TearFree" "true"
>
> my video tearing problem disappears, but if I close my laptop lid for
> a few minutes, it comes back up with a black screen, although I can
> get my session back if I switch to VT1 and then back to VT7.  I can't
> find anything in the logs.  I've tried xf86-video-intel-2.20.3 as well
> as the latest from git.  The problem doesn't occur without the above
> two directives.
>
> Does anyone know how to diagnose or fix this?
>
> - Grant

I can prevent this if I issue 'xset -dpms' before closing the laptop
lid, but xlockmore automatically re-enables dpms unfortunately.  BTW,
this does not prevent the problem:

DPMS (Energy Star):
  Standby: 0    Suspend: 0    Off: 0
  DPMS is Enabled
  Monitor is On

It has to be this:

DPMS (Energy Star):
  Standby: 0    Suspend: 0    Off: 0
  DPMS is Disabled

I've tried different kernel versions as well as different versions of
xf86-video-intel and xorg-server with the same result.

- Grant