drm/i915/gen9: only add the planes actually affected by ddb changes

commit be5c571b upstream.

We were previously adding all the planes owned by the CRTC even when
the ddb partitioning didn't change for them. As a consequence, a lot
of functions were being called when we were just moving the cursor
around the screen, such as skylake_update_primary_plane().

This was causing flickering on the primary plane when moving the
cursor. I'm not 100% sure which operation caused the flickering, but
we were writing to a lot of registers, so it could be any of these
writes. With this patch, just moving the mouse won't add the primary
plane to the commit since it won't trigger a change in DDB
partitioning.

v2: Use skl_ddb_entry_equal() (Lyude).
v3: Change Reported-and-bisected-by: to Reported-by: for checkpatch

Fixes: 05a76d3d ("drm/i915/skl: Ensure pipes with changed wms get added to the state")
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=97888
Cc: Mike Lothian <mike@fireburn.co.uk>
Reported-by: Mike Lothian <mike@fireburn.co.uk>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Lyude <cpaul@redhat.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1475177808-29955-1-git-send-email-paulo.r.zanoni@intel.com
(cherry picked from commit 7f60e200)
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/gpu/drm/i915/intel_pm.c

@@ -3940,6 +3940,41 @@ pipes_modified(struct drm_atomic_state *state)
 	return ret;
 }
 
+int
+skl_ddb_add_affected_planes(struct intel_crtc_state *cstate)
+{
+	struct drm_atomic_state *state = cstate->base.state;
+	struct drm_device *dev = state->dev;
+	struct drm_crtc *crtc = cstate->base.crtc;
+	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
+	struct drm_i915_private *dev_priv = to_i915(dev);
+	struct intel_atomic_state *intel_state = to_intel_atomic_state(state);
+	struct skl_ddb_allocation *new_ddb = &intel_state->wm_results.ddb;
+	struct skl_ddb_allocation *cur_ddb = &dev_priv->wm.skl_hw.ddb;
+	struct drm_plane_state *plane_state;
+	struct drm_plane *plane;
+	enum pipe pipe = intel_crtc->pipe;
+	int id;
+
+	WARN_ON(!drm_atomic_get_existing_crtc_state(state, crtc));
+
+	drm_for_each_plane_mask(plane, dev, crtc->state->plane_mask) {
+		id = skl_wm_plane_id(to_intel_plane(plane));
+
+		if (skl_ddb_entry_equal(&cur_ddb->plane[pipe][id],
+					&new_ddb->plane[pipe][id]) &&
+		    skl_ddb_entry_equal(&cur_ddb->y_plane[pipe][id],
+					&new_ddb->y_plane[pipe][id]))
+			continue;
+
+		plane_state = drm_atomic_get_plane_state(state, plane);
+		if (IS_ERR(plane_state))
+			return PTR_ERR(plane_state);
+	}
+
+	return 0;
+}
+
 static int
 skl_compute_ddb(struct drm_atomic_state *state)
 {
@@ -4004,7 +4039,7 @@ skl_compute_ddb(struct drm_atomic_state *state)
 		if (ret)
 			return ret;
 
-		ret = drm_atomic_add_affected_planes(state, &intel_crtc->base);
+		ret = skl_ddb_add_affected_planes(cstate);
 		if (ret)
 			return ret;
 	}