[Intel-gfx] [PATCH] drm/i915/gen9: only add the planes actually affected by ddb changes

[Paulo Zanoni]

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.

Fixes: 05a76d3d6ad1 ("drm/i915/skl: Ensure pipes with changed wms get
added to the state")

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=97888
Cc: Lyude <cpaul at redhat.com>
Cc: Mike Lothian <mike at fireburn.co.uk>
Cc: stable at vger.kernel.org
Reported-and-bisected-by: Mike Lothian <mike at fireburn.co.uk>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni at intel.com>
---
 drivers/gpu/drm/i915/intel_pm.c | 41 ++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 40 insertions(+), 1 deletion(-)


I can confirm this fixes the flickering I was seeing.


diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index 5d39ad2..1cf34a3 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3966,6 +3966,45 @@ 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 (cur_ddb->plane[pipe][id].start ==
+		    new_ddb->plane[pipe][id].start &&
+		    cur_ddb->plane[pipe][id].end ==
+		    new_ddb->plane[pipe][id].end &&
+		    cur_ddb->y_plane[pipe][id].start ==
+		    new_ddb->y_plane[pipe][id].start &&
+		    cur_ddb->y_plane[pipe][id].end ==
+		    new_ddb->y_plane[pipe][id].end)
+			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)
 {
@@ -4030,7 +4069,7 @@ 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;
 	}
-- 
2.7.4