[Intel-gfx] [PATCH v2 12/14] drm/i915/fbc: Wait for vblank after FBC disable on glk+

[Ville Syrjala]

From: Ville Syrjälä <ville.syrjala at linux.intel.com>

On glk+ the hardware gets confused if we disable FBC while
it's recompressing and we perform a plane update during the
same frame. The result is that top of the screen gets corrupted.

We can avoid that by giving the hardware enough time to finish
the FBC disable before we touch the plane registers. Ie. we need
an extra vblank wait after FBC disable.

Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
---
 drivers/gpu/drm/i915/display/intel_display.c |  4 ++-
 drivers/gpu/drm/i915/display/intel_fbc.c     | 26 +++++++++++++++++---
 drivers/gpu/drm/i915/display/intel_fbc.h     |  2 +-
 3 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_display.c b/drivers/gpu/drm/i915/display/intel_display.c
index d592b7284406..3210a0f00009 100644
--- a/drivers/gpu/drm/i915/display/intel_display.c
+++ b/drivers/gpu/drm/i915/display/intel_display.c
@@ -6105,7 +6105,9 @@ static void intel_pre_plane_update(struct intel_crtc_state *old_crtc_state,
 			intel_atomic_get_new_plane_state(intel_state,
 							 to_intel_plane(primary));
 
-		intel_fbc_pre_update(crtc, pipe_config, new_primary_state);
+		if (intel_fbc_pre_update(crtc, pipe_config, new_primary_state))
+			intel_wait_for_vblank(dev_priv, crtc->pipe);
+
 		/*
 		 * Gen2 reports pipe underruns whenever all planes are disabled.
 		 * So disable underrun reporting before all the planes get disabled.
diff --git a/drivers/gpu/drm/i915/display/intel_fbc.c b/drivers/gpu/drm/i915/display/intel_fbc.c
index 220fbe5bd919..78fe4abb5a93 100644
--- a/drivers/gpu/drm/i915/display/intel_fbc.c
+++ b/drivers/gpu/drm/i915/display/intel_fbc.c
@@ -859,16 +859,17 @@ static bool intel_fbc_can_flip_nuke(const struct intel_crtc_state *crtc_state)
 	return true;
 }
 
-void intel_fbc_pre_update(struct intel_crtc *crtc,
+bool intel_fbc_pre_update(struct intel_crtc *crtc,
 			  struct intel_crtc_state *crtc_state,
 			  struct intel_plane_state *plane_state)
 {
 	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
 	struct intel_fbc *fbc = &dev_priv->fbc;
 	const char *reason = "update pending";
+	bool need_vblank_wait = false;
 
 	if (!fbc_supported(dev_priv))
-		return;
+		return need_vblank_wait;
 
 	mutex_lock(&fbc->lock);
 
@@ -878,10 +879,29 @@ void intel_fbc_pre_update(struct intel_crtc *crtc,
 	intel_fbc_update_state_cache(crtc, crtc_state, plane_state);
 	fbc->flip_pending = true;
 
-	if (!intel_fbc_can_flip_nuke(crtc_state))
+	if (!intel_fbc_can_flip_nuke(crtc_state)) {
 		intel_fbc_deactivate(dev_priv, reason);
+
+		/*
+		 * Display WA #1198: glk+
+		 * Need an extra vblank wait between FBC disable and most plane
+		 * updates. Bspec says this is only needed for plane disable, but
+		 * that is not true. Touching most plane registers will cause the
+		 * corruption to appear. Also SKL/derivatives do not seem to be
+		 * affected.
+		 *
+		 * TODO: could optimize this a bit by sampling the frame
+		 * counter when we disable FBC (if it was already done earlier)
+		 * and skipping the extra vblank wait before the plane update
+		 * if at least one frame has already passed.
+		 */
+		if (INTEL_GEN(dev_priv) >= 10 || IS_GEMINILAKE(dev_priv))
+			need_vblank_wait = true;
+	}
 unlock:
 	mutex_unlock(&fbc->lock);
+
+	return need_vblank_wait;
 }
 
 /**
diff --git a/drivers/gpu/drm/i915/display/intel_fbc.h b/drivers/gpu/drm/i915/display/intel_fbc.h
index ba8eeefd4d9a..9a2f1094cbda 100644
--- a/drivers/gpu/drm/i915/display/intel_fbc.h
+++ b/drivers/gpu/drm/i915/display/intel_fbc.h
@@ -19,7 +19,7 @@ struct intel_plane_state;
 void intel_fbc_choose_crtc(struct drm_i915_private *dev_priv,
 			   struct intel_atomic_state *state);
 bool intel_fbc_is_active(struct drm_i915_private *dev_priv);
-void intel_fbc_pre_update(struct intel_crtc *crtc,
+bool intel_fbc_pre_update(struct intel_crtc *crtc,
 			  struct intel_crtc_state *crtc_state,
 			  struct intel_plane_state *plane_state);
 void intel_fbc_post_update(struct intel_crtc *crtc);
-- 
2.23.0