drm/i915: remove the vblank_wait hack from HSW+

When I forked haswell_crtc_enable I copied all the code from
ironlake_crtc_enable. The last piece of the function contains a big
comment with a call to intel_wait_for_vblank. After this fork, we
rearranged the Haswell code so that it enables the planes as the very
last step of the modeset sequence, so we're sure that we call
intel_enable_primary_plane after the pipe is really running, so the
vblank waiting functions work as expected. I really believe this is
what fixes the problem described by the big comment, so let's give it
a try and get rid of that intel_wait_for_vblank, saving around 16ms
per modeset (and init/resume). We can always revert if needed :)
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_display.c

@@ -3761,16 +3761,6 @@ static void haswell_crtc_enable(struct drm_crtc *crtc)
 	 * to change the workaround. */
 	haswell_mode_set_planes_workaround(intel_crtc);
 	haswell_crtc_enable_planes(crtc);
-
-	/*
-	 * There seems to be a race in PCH platform hw (at least on some
-	 * outputs) where an enabled pipe still completes any pageflip right
-	 * away (as if the pipe is off) instead of waiting for vblank. As soon
-	 * as the first vblank happend, everything works as expected. Hence just
-	 * wait for one vblank before returning to avoid strange things
-	 * happening.
-	 */
-	intel_wait_for_vblank(dev, intel_crtc->pipe);
 }
 
 static void ironlake_pfit_disable(struct intel_crtc *crtc)