[Intel-gfx] [PATCH 6/7] drm/i915/fbc: move from crtc_state->enable_fbc to plane_state->enable_fbc

[Paulo Zanoni]

Ville pointed out that intel_fbc_choose_crtc() is iterating over all
planes instead of just the primary planes. There are no real
consequences of this problem for HSW+, and for the other platforms it
just means that in some obscure multi-screen cases we'll keep FBC
disabled when we could have enabled it. Still, iterating over all
planes doesn't seem to be the best thing to do.

My initial idea was to just add a check for plane->type and be done,
but then I realized that in commits not involving the primary plane we
would reset crtc_state->enable_fbc back to false even when FBC is
enabled. That also wouldn't result in a bug due to the way the
enable_fbc variable is checked, but, still, our code can be better
than this.

So I went for the solution that involves tracking enable_fbc in the
primary plane state instead of the CRTC state. This way, if a commit
doesn't involve the primary plane for the CRTC we won't be resetting
enable_fbc back to false, so the variable will always reflect the
reality. And this change also makes more sense since FBC is actually
tied to the single plane and not the full pipe. As a bonus, we only
iterate over the CRTCs instead of iterating over all planes.

Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
Reported-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
Signed-off-by: Paulo Zanoni <paulo.r.zanoni at intel.com>
---
 drivers/gpu/drm/i915/intel_drv.h |  4 ++--
 drivers/gpu/drm/i915/intel_fbc.c | 36 +++++++++++++++++++-----------------
 2 files changed, 21 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index 003afb8..025cb74 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -403,6 +403,8 @@ struct intel_plane_state {
 	int scaler_id;
 
 	struct drm_intel_sprite_colorkey ckey;
+
+	bool enable_fbc;
 };
 
 struct intel_initial_plane_config {
@@ -648,8 +650,6 @@ struct intel_crtc_state {
 
 	bool ips_enabled;
 
-	bool enable_fbc;
-
 	bool double_wide;
 
 	bool dp_encoder_is_mst;
diff --git a/drivers/gpu/drm/i915/intel_fbc.c b/drivers/gpu/drm/i915/intel_fbc.c
index b095175..fc4ac57 100644
--- a/drivers/gpu/drm/i915/intel_fbc.c
+++ b/drivers/gpu/drm/i915/intel_fbc.c
@@ -1055,16 +1055,17 @@ void intel_fbc_choose_crtc(struct drm_i915_private *dev_priv,
 			   struct drm_atomic_state *state)
 {
 	struct intel_fbc *fbc = &dev_priv->fbc;
-	struct drm_plane *plane;
-	struct drm_plane_state *plane_state;
+	struct drm_crtc *crtc;
+	struct drm_crtc_state *crtc_state;
 	bool crtc_chosen = false;
 	int i;
 
 	mutex_lock(&fbc->lock);
 
-	/* Does this atomic commit involve the CRTC currently tied to FBC? */
+	/* Does this atomic commit involve the plane currently tied to FBC? */
 	if (fbc->crtc &&
-	    !drm_atomic_get_existing_crtc_state(state, &fbc->crtc->base))
+	    !drm_atomic_get_existing_plane_state(state,
+						 fbc->crtc->base.primary))
 		goto out;
 
 	if (!intel_fbc_can_enable(dev_priv))
@@ -1074,25 +1075,26 @@ void intel_fbc_choose_crtc(struct drm_i915_private *dev_priv,
 	 * plane. We could go for fancier schemes such as checking the plane
 	 * size, but this would just affect the few platforms that don't tie FBC
 	 * to pipe or plane A. */
-	for_each_plane_in_state(state, plane, plane_state, i) {
-		struct intel_plane_state *intel_plane_state =
-			to_intel_plane_state(plane_state);
-		struct intel_crtc_state *intel_crtc_state;
-		struct intel_crtc *crtc = to_intel_crtc(plane_state->crtc);
+	for_each_crtc_in_state(state, crtc, crtc_state, i) {
+		struct intel_plane_state *plane_state = to_intel_plane_state(
+			drm_atomic_get_existing_plane_state(state,
+							    crtc->primary));
+		struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
 
-		if (!intel_plane_state->base.visible)
+		if (!plane_state)
 			continue;
 
-		if (fbc_on_pipe_a_only(dev_priv) && crtc->pipe != PIPE_A)
+		if (!plane_state->base.visible)
 			continue;
 
-		if (fbc_on_plane_a_only(dev_priv) && crtc->plane != PLANE_A)
+		if (fbc_on_pipe_a_only(dev_priv) && intel_crtc->pipe != PIPE_A)
 			continue;
 
-		intel_crtc_state = to_intel_crtc_state(
-			drm_atomic_get_existing_crtc_state(state, &crtc->base));
+		if (fbc_on_plane_a_only(dev_priv) &&
+		    intel_crtc->plane != PLANE_A)
+			continue;
 
-		intel_crtc_state->enable_fbc = true;
+		plane_state->enable_fbc = true;
 		crtc_chosen = true;
 		break;
 	}
@@ -1130,13 +1132,13 @@ void intel_fbc_enable(struct intel_crtc *crtc,
 	if (fbc->enabled) {
 		WARN_ON(fbc->crtc == NULL);
 		if (fbc->crtc == crtc) {
-			WARN_ON(!crtc_state->enable_fbc);
+			WARN_ON(!plane_state->enable_fbc);
 			WARN_ON(fbc->active);
 		}
 		goto out;
 	}
 
-	if (!crtc_state->enable_fbc)
+	if (!plane_state->enable_fbc)
 		goto out;
 
 	WARN_ON(fbc->active);
-- 
2.7.4