drm/atomic: Add encoder_mask to crtc_state, v3.

This allows iteration over encoders without requiring connection_mutex.

Changes since v1:
- Add a set_best_encoder helper function and update encoder_mask inside
it.
Changes since v2:
- Relax the WARN_ON(!crtc), with explanation.
- Call set_best_encoder when connector is moved between crtc's.
- Add some paranoia to steal_encoder to prevent accidentally setting
best_encoder to NULL.

Signed-off-by: Maarten Lankhorst <[e-mail]>
Reviewed-by: Gustavo Padovan <[e-mail]>
Signed-off-by: Daniel Vetter <[e-mail]>
Link: http://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/drm_atomic_helper.c

···
 	return NULL;
 }
 
+static void
+set_best_encoder(struct drm_atomic_state *state,
+		 struct drm_connector_state *conn_state,
+		 struct drm_encoder *encoder)
+{
+	struct drm_crtc_state *crtc_state;
+	struct drm_crtc *crtc;
+
+	if (conn_state->best_encoder) {
+		/* Unset the encoder_mask in the old crtc state. */
+		crtc = conn_state->connector->state->crtc;
+
+		/* A NULL crtc is an error here because we should have
+		 *  duplicated a NULL best_encoder when crtc was NULL.
+		 * As an exception restoring duplicated atomic state
+		 * during resume is allowed, so don't warn when
+		 * best_encoder is equal to encoder we intend to set.
+		 */
+		WARN_ON(!crtc && encoder != conn_state->best_encoder);
+		if (crtc) {
+			crtc_state = drm_atomic_get_existing_crtc_state(state, crtc);
+
+			crtc_state->encoder_mask &=
+				~(1 << drm_encoder_index(conn_state->best_encoder));
+		}
+	}
+
+	if (encoder) {
+		crtc = conn_state->crtc;
+		WARN_ON(!crtc);
+		if (crtc) {
+			crtc_state = drm_atomic_get_existing_crtc_state(state, crtc);
+
+			crtc_state->encoder_mask |=
+				1 << drm_encoder_index(encoder);
+		}
+	}
+
+	conn_state->best_encoder = encoder;
+}
+
 static int
 steal_encoder(struct drm_atomic_state *state,
 	      struct drm_encoder *encoder,
···
 		if (IS_ERR(connector_state))
 			return PTR_ERR(connector_state);
 
-		connector_state->best_encoder = NULL;
+		if (connector_state->best_encoder != encoder)
+			continue;
+
+		set_best_encoder(state, connector_state, NULL);
 	}
 
 	return 0;
···
 				connector->base.id,
 				connector->name);
 
-		connector_state->best_encoder = NULL;
+		set_best_encoder(state, connector_state, NULL);
 
 		return 0;
 	}
···
 	}
 
 	if (new_encoder == connector_state->best_encoder) {
+		set_best_encoder(state, connector_state, new_encoder);
+
 		DRM_DEBUG_ATOMIC("[CONNECTOR:%d:%s] keeps [ENCODER:%d:%s], now on [CRTC:%d:%s]\n",
 				 connector->base.id,
 				 connector->name,
···
 	if (WARN_ON(!connector_state->crtc))
 		return -EINVAL;
 
-	connector_state->best_encoder = new_encoder;
+	set_best_encoder(state, connector_state, new_encoder);
+
 	idx = drm_crtc_index(connector_state->crtc);
 
 	crtc_state = state->crtc_states[idx];

drivers/gpu/drm/i915/intel_display.c

···
 		crtc->base.state->active = crtc->active;
 		crtc->base.enabled = crtc->active;
 		crtc->base.state->connector_mask = 0;
+		crtc->base.state->encoder_mask = 0;
 
 		/* Because we only establish the connector -> encoder ->
 		 * crtc links if something is active, this means the
···
 				 */
 				encoder->base.crtc->state->connector_mask |=
 					1 << drm_connector_index(&connector->base);
+				encoder->base.crtc->state->encoder_mask |=
+					1 << drm_encoder_index(&encoder->base);
 			}
 
 		} else {

include/drm/drm_crtc.h

···
  * @connectors_changed: connectors to this crtc have been updated
  * @plane_mask: bitmask of (1 << drm_plane_index(plane)) of attached planes
  * @connector_mask: bitmask of (1 << drm_connector_index(connector)) of attached connectors
+ * @encoder_mask: bitmask of (1 << drm_encoder_index(encoder)) of attached encoders
  * @last_vblank_count: for helpers and drivers to capture the vblank of the
  * 	update to ensure framebuffer cleanup isn't done too early
  * @adjusted_mode: for use by helpers and drivers to compute adjusted mode timings
···
 	u32 plane_mask;
 
 	u32 connector_mask;
+	u32 encoder_mask;
 
 	/* last_vblank_count: for vblank waits before cleanup */
 	u32 last_vblank_count;