[PATCH 00/13] drm/i915: Non-blocking GPU synchronization for atomic page flips (v2)

[ville.syrjala at linux.intel.com]

Here's my second attempt at making atomic page flips synchronize with the
GPU in a non-blocking manner.

What the code does by default is grap the last_write_seqno from the object,
call intel_gem_check_olr() on it, perform the lazy coherency check, and
if the seqno still hasn't passed it'll enable the irq and let that sort
things out. Now, I'm not sure if the call to intel_gem_check_olr() is even
necessary in practice, or can I just go on to checking the seqno directly.

With some earlier patches I was seeing an occasional glitch on my screen,
and so I tried out a few different variations (always adding a new request
to the ring and forcing a GPU cache flush), and for now I left that code
in there under a bunch of ifdefs. The glitch was probably caused by
committing the wrong register values to the hardware, and patch 05/13
should fix that. I haven't seen any issues for a while now.

The real meat is at the beginning of the patch set, and the second half
contains just debugging aids.

Oh, and I rebased the whole thing on top of drm-intel-nightly yesterday. The
haswell changes gave me a bit of grief, but I think I managed to preserve all
of them, and still make the atomic stuff work. But I haven't actually tried
running it on hsw hardware.

Besides my own tests, I also gave Ander's nuclear-pageflip branch of weston [1]
a go on top of this stuff. Seems to be working quite nicely so far. Now I just
need a working browser and sloppy focus, and I can ditch X ;)

As usual my git tree [2] has the whole set for easier consumption.

[1] https://github.com/anderco/weston/tree/nuclear-pageflip
[2] https://gitorious.org/vsyrjala/linux/commits/drm_atomic_21