i945GM don't show video at vga port (blue screen)

[Drew Parsons]

On Tue, 2007-06-05 at 00:14 -0700, Keith Packard wrote:
> On Thu, 2007-05-31 at 14:48 +0800, Wang Zhenyu wrote:
> 
> > Yes, it looks like in i830_crtc_dpms_video() after we stop video, overlayOK is 
> > false, and later if we want to turn video on, it will fail in 
> > 	if (crtc != pPriv->current_crtc)
> > 	    return;
> > as current pipe is changed. So overlayOK will never be turned true. 
> 
> Fixed in git master. I'm fairly happy at this point; the only known
> breakage is with rotation (which doesn't appear to work at all).
> 

Confirmed this fixes the LVDS blue screen problem.  I can now get
1) Laptop screen alone, Xv video plays ok on LVDS.
2) Laptop + external monitor, video plays on VGA, LVDS displays blue.
3) Back to laptop alone, video plays once again on LVDS.

Thanks for the great work, Keith!

There is some kind of instability in switching between one screen (LVDS)
and two (LVDS+VGA), and backwards and forwards.  The first switch seems
stable, but with the second and then third switch the system
occasionally freezes solid.  I suspect this is not necessarily related
to the new Xv fixes since I've been seeing something like this for a
while now.  I think it's only paining me now because I'm deliberately
switching back&forth rapidly to test the Xv behaviour.  

It does not happen every single time so I'm not sure exactly where the
reproducibility is.  I seem to most often be able to go from one screen
to two and back to one, then the freeze occurs returning back to two
again.  But sometimes it happens just going from one to two and back to
one again.  If I can pin it down I'll file a separate bug.  It seems to
be triggered by running xrandr (which I need to run in order to readapt
to the new number of screen).

Drew