[PATCH 4/5] drm/i915: Add async page flip support for IVB

[Keith Packard]

> Generally I think checking our current sw state instead of reading hw
> registers would be safer, e.g. in case we start to queue up more than
> one pageflip. For async pageflips in benchmark mode "flip as fast as
> you can queue" would be a sensible mode.

Ok, I've moved the tiling checks to the general code and removed the
stride checks as those are already present there. These were moved to
the general code because the pointer to the previous FB has already
been overwritten by the time the queue_flip functions are called.

This should be followed by replacements for the last to patches in the
series.

-keith