From: Chris Wilson <ch...@chris-wilson.co.uk>

intel_fbc_pre_update() depends upon the new state being already pinned
in place in the Global GTT (primarily for both fencing which wants both
an offset and a fence register, if assigned). This requires the call to
intel_fbc_pre_update() be after intel_pin_and_fence_fb() - but commit
e8216e502aca ("drm/i915/fbc: call intel_fbc_pre_update earlier during
page flips") moved the code way too much up in its attempt to call it
before the page flip.

v2 (from Paulo):
 - Point the original bad commit.
 - Add a comment to maybe prevent further regressions.

Fixes: e8216e502aca ("drm/i915/fbc: call intel_fbc_pre_update earlier...")
Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
Signed-off-by: Paulo Zanoni <paulo.r.zan...@intel.com>
Cc: Daniel Vetter <daniel.vet...@intel.com>
Cc: Ville Syrjälä <ville.syrj...@linux.intel.com>
Cc: Maarten Lankhorst <maarten.lankho...@linux.intel.com>
Cc: Patrik Jakobsson <patrik.jakobs...@linux.intel.com>
Cc: drm-intel-fi...@lists.freedesktop.org
---
 drivers/gpu/drm/i915/intel_display.c | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c 
b/drivers/gpu/drm/i915/intel_display.c
index 8a203b5..7057bd9 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -12109,9 +12109,6 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
        crtc->primary->fb = fb;
        update_state_fb(crtc->primary);
 
-       intel_fbc_pre_update(intel_crtc, intel_crtc->config,
-                            to_intel_plane_state(primary->state));
-
        work->pending_flip_obj = i915_gem_object_get(obj);
 
        ret = i915_mutex_lock_interruptible(dev);
@@ -12157,6 +12154,17 @@ static int intel_crtc_page_flip(struct drm_crtc *crtc,
        work->gtt_offset += intel_crtc->dspaddr_offset;
        work->rotation = crtc->primary->state->rotation;
 
+       /*
+        * There's the potential that the next frame will not be compatible with
+        * FBC, so we want to call pre_update() before the actual page flip.
+        * The problem is that pre_update() caches some information about the fb
+        * object, so we want to do this only after the object is pinned. Let's
+        * be on the safe side and do this immediately before scheduling the
+        * flip.
+        */
+       intel_fbc_pre_update(intel_crtc, intel_crtc->config,
+                            to_intel_plane_state(primary->state));
+
        if (mmio_flip) {
                INIT_WORK(&work->mmio_work, intel_mmio_flip_work_func);
 
-- 
2.7.4

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