[PATCH 0/3] Enable both asynchronous and synchronous plane flip

[Colin Xu]

Write to GEN graphics display register PLANE_SURF is considered a plane flip,
which can be done either through command streamer or MMIO write synchronously
or asynchronously. Synchronous updates will update the plane surface values
at the start of the next vertical blank to prevent screen tearing, while
asynchronous updates will update the plane surface as soon as possible for
faster screen update. The behaviour depends on MI_DISPLAY_FLIP command or
plane control register.

There also exist some mistakes on emulating pipe frame count and pipe flip
count increment:
- pipe frame count should only get incremented on every start of vsync, not
  on plane flip.
- pipe flip count indicates the start of flip when the plane surface
  address is updated, not when the flip completes.
- On GVT currently supported platforms including BDW and SKL+, pipe flip
  count only count flips of primary plane.
Relevant information can be found on Intel GFX PRM on 01.org.

The patch set enables asynchronous plane flip for both MI_DISPLAY_FLIP
update and plane surface address mmio update. With the patch, the render
performance of some 3D application especially benchmark tools can be
increased significantly. 
An experiment tested on gvt-staging (5.0.0-RC4):
Host: Intel CFL NUC (i7-8559U, 16GB memory)
Guest: 2 VCPU, 4096MB memory, Type-4 VGPU, dmabuf
Benchmark: 3DMark IceStorm on Windows 10.0.17134

+----------------+-----------+------------+
|   Test Item    |  Before   |   After    |
+----------------+-----------+------------+
| Graphics score | 14346     | 55387      |
| Graphic test 1 | 62.36 FPS | 252.65 FPS |
| Graphic test 2 | 62.39 FPS | 230.04 FPS |
| Physical score | 19688     | 26665      |
| Physical test  | 62.50 FPS | 84.65 FPS  |
+----------------+-----------+------------+

Colin Xu (3):
  drm/i915/gvt: Add macro define for mmio 0x50080 and gvt flip event
  drm/i915/gvt: Enable synchronous flip on handling MI_DISPLAY_FLIP
  drm/i915/gvt: Enable async flip on plane surface mmio writes

 drivers/gpu/drm/i915/gvt/cmd_parser.c | 10 ++-
 drivers/gpu/drm/i915/gvt/display.c    |  1 -
 drivers/gpu/drm/i915/gvt/handlers.c   | 99 ++++++++++++++++++++++-----
 drivers/gpu/drm/i915/gvt/reg.h        | 27 ++++++++
 4 files changed, 116 insertions(+), 21 deletions(-)

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2.21.0