[Intel-gfx] [PATCH] drm/i915: Do not set "Enable Panel Fitter" on SNB pageflips

[Chris Wilson]

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 at redhat.com>
Cc: Adam Jackson <ajax at redhat.com>
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/intel_display.c |    8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index b2c29a5..2319838 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -7902,7 +7902,13 @@ 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();
-- 
1.7.10