drm/atomic: Handle encoder stealing from set_config better.

Instead of failing with -EINVAL when conflicting encoders are found,
the legacy set_config will disable other connectors when encoders
conflict.

With the previous commit this becomes a lot easier to implement.
set_config only adds connectors to the state that are modified,
and because of the previous commit that calls add_affected_connectors
only on set->crtc it means any connector not part of the modeset can
be stolen from. We disable the connector in that case, and possibly
the crtc if required.

Atomic modeset itself still doesn't allow encoder stealing, the results
would be too unpredictable.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1456996662-8704-5-git-send-email-maarten.lankhorst@linux.intel.com

drivers/gpu/drm/drm_atomic_helper.c

@@ -86,6 +86,68 @@ drm_atomic_helper_plane_changed(struct drm_atomic_state *state,
 	}
 }
 
+static int disable_conflicting_connectors(struct drm_atomic_state *state)
+{
+	struct drm_connector_state *conn_state;
+	struct drm_connector *connector;
+	struct drm_encoder *encoder;
+	unsigned encoder_mask = 0;
+	int i, ret;
+
+	for_each_connector_in_state(state, connector, conn_state, i) {
+		const struct drm_connector_helper_funcs *funcs = connector->helper_private;
+		struct drm_encoder *new_encoder;
+
+		if (!conn_state->crtc)
+			continue;
+
+		if (funcs->atomic_best_encoder)
+			new_encoder = funcs->atomic_best_encoder(connector, conn_state);
+		else
+			new_encoder = funcs->best_encoder(connector);
+
+		if (new_encoder)
+			encoder_mask |= 1 << drm_encoder_index(new_encoder);
+	}
+
+	drm_for_each_connector(connector, state->dev) {
+		struct drm_crtc_state *crtc_state;
+
+		if (drm_atomic_get_existing_connector_state(state, connector))
+			continue;
+
+		encoder = connector->state->best_encoder;
+		if (!encoder || !(encoder_mask & (1 << drm_encoder_index(encoder))))
+			continue;
+
+		conn_state = drm_atomic_get_connector_state(state, connector);
+		if (IS_ERR(conn_state))
+			return PTR_ERR(conn_state);
+
+		DRM_DEBUG_ATOMIC("[ENCODER:%d:%s] in use on [CRTC:%d:%s], disabling [CONNECTOR:%d:%s]\n",
+				 encoder->base.id, encoder->name,
+				 conn_state->crtc->base.id, conn_state->crtc->name,
+				 connector->base.id, connector->name);
+
+		crtc_state = drm_atomic_get_existing_crtc_state(state, conn_state->crtc);
+
+		ret = drm_atomic_set_crtc_for_connector(conn_state, NULL);
+		if (ret)
+			return ret;
+
+		if (!crtc_state->connector_mask) {
+			ret = drm_atomic_set_mode_prop_for_crtc(crtc_state,
+								NULL);
+			if (ret < 0)
+				return ret;
+
+			crtc_state->active = false;
+		}
+	}
+
+	return 0;
+}
+
 static bool
 check_pending_encoder_assignment(struct drm_atomic_state *state,
 				 struct drm_encoder *new_encoder)
@@ -448,6 +510,12 @@ drm_atomic_helper_check_modeset(struct drm_device *dev,
 		}
 	}
 
+	if (state->legacy_set_config) {
+		ret = disable_conflicting_connectors(state);
+		if (ret)
+			return ret;
+	}
+
 	for_each_connector_in_state(state, connector, connector_state, i) {
 		/*
 		 * This only sets crtc->mode_changed for routing changes,
@@ -1796,6 +1864,7 @@ int drm_atomic_helper_set_config(struct drm_mode_set *set)
 	if (!state)
 		return -ENOMEM;
 
+	state->legacy_set_config = true;
 	state->acquire_ctx = drm_modeset_legacy_acquire_ctx(crtc);
 retry:
 	ret = __drm_atomic_helper_set_config(set, state);

include/drm/drm_crtc.h

@@ -1676,6 +1676,7 @@ struct drm_bridge {
  * @dev: parent DRM device
  * @allow_modeset: allow full modeset
  * @legacy_cursor_update: hint to enforce legacy cursor IOCTL semantics
+ * @legacy_set_config: Disable conflicting encoders instead of failing with -EINVAL.
  * @planes: pointer to array of plane pointers
  * @plane_states: pointer to array of plane states pointers
  * @crtcs: pointer to array of CRTC pointers
@@ -1689,6 +1690,7 @@ struct drm_atomic_state {
 	struct drm_device *dev;
 	bool allow_modeset : 1;
 	bool legacy_cursor_update : 1;
+	bool legacy_set_config : 1;
 	struct drm_plane **planes;
 	struct drm_plane_state **plane_states;
 	struct drm_crtc **crtcs;