i915 powersave/fbc issues on i945 and older

[Andy Whitcroft]

We have been seeing a return of the hanging and going solid colours and
generally jumping about oddly behaviour since the update to DRM 2.6.33.
This seems to be limited to older cards this time, it appears to work
on cards after i945.

I have put together a patch to disable powersaving completely for all
cards i945gm and older.  Kernels with this patch applied are available
at the URL below:

    http://people.canonical.com/~apw/i915-powersave-broken-lucid/

If people could try this out on their card and report the contents of
their 'dynamic power saving' line that would be helpful.  For those with
older cards if you have seen these issues please test to see if they are
resolved:

    [    4.719350] [drm] dynamic power saving: broken=1 enabled=0

Also there are rumours that disabling framebuffer compression only might
also help the issue.  Here is a patch stolen from Sarvatt which just
turns that off which is also worth testing if you experience these
issues:

    http://people.canonical.com/~apw/i915-fbc-broken-lucid/

Please test and report back here.  Thanks!

-apw