drm/i915: Do not set "Enable Panel Fitter" on SNB pageflips

Not only do the pageflip work without it at non-native modes (i.e. with
the panel fitter enabled), it also causes normal (non-pageflipped)
modesets to fail.

Reported-by: Adam Jackson <ajax@redhat.com>
Tested-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Wanted-by-for-fixes: Dave Airlie <airlied@gmail.com>
Signed-Off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 7 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 8be30917bce3..5908cd563400 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -7468,7 +7468,13 @@ static int intel_gen6_queue_flip(struct drm_device *dev,
         OUT_RING(fb->pitches[0] | obj->tiling_mode);
         OUT_RING(obj->gtt_offset);
 
-        pf = I915_READ(PF_CTL(intel_crtc->pipe)) & PF_ENABLE;
+        /* Contrary to the suggestions in the documentation,
+         * "Enable Panel Fitter" does not seem to be required when page
+         * flipping with a non-native mode, and worse causes a normal
+         * modeset to fail.
+         * pf = I915_READ(PF_CTL(intel_crtc->pipe)) & PF_ENABLE;
+         */
+        pf = 0;
         pipesrc = I915_READ(PIPESRC(intel_crtc->pipe)) & 0x0fff0fff;
         OUT_RING(pf | pipesrc);
         ADVANCE_LP_RING();