[PATCH 13/15] drm: take references to connectors used in a modeset.

[Dave Airlie]

From: Dave Airlie <airlied at redhat.com>

As suggested by Daniel, if we are actively using the connector in a modeset
we don't want it to disappear from underneath us. This takes a reference
to the connector in the atomic paths when we are setting the state up,
and in the non-atomic paths when binding the encoder.

Signed-off-by: Dave Airlie <airlied at redhat.com>
---
 drivers/gpu/drm/drm_atomic.c      | 11 ++++++++++-
 drivers/gpu/drm/drm_crtc_helper.c |  6 ++++++
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_atomic.c b/drivers/gpu/drm/drm_atomic.c
index 9d5e3c8..d899dac 100644
--- a/drivers/gpu/drm/drm_atomic.c
+++ b/drivers/gpu/drm/drm_atomic.c
@@ -1159,7 +1159,7 @@ drm_atomic_set_crtc_for_connector(struct drm_connector_state *conn_state,
 				  struct drm_crtc *crtc)
 {
 	struct drm_crtc_state *crtc_state;
-
+	bool had_crtc = conn_state->crtc ? true : false;
 	if (conn_state->crtc && conn_state->crtc != crtc) {
 		crtc_state = drm_atomic_get_existing_crtc_state(conn_state->state,
 								conn_state->crtc);
@@ -1179,6 +1179,15 @@ drm_atomic_set_crtc_for_connector(struct drm_connector_state *conn_state,
 
 	conn_state->crtc = crtc;
 
+	/* If we had no crtc then got one, add a reference,
+	 * if we had a crtc and are going to none, drop a reference,
+	 * otherwise just keep the reference we have.
+	 */
+	if (!had_crtc && crtc)
+		drm_connector_reference(conn_state->connector);
+	else if (!crtc && had_crtc)
+		 drm_connector_unreference(conn_state->connector);
+
 	if (crtc)
 		DRM_DEBUG_ATOMIC("Link connector state %p to [CRTC:%d:%s]\n",
 				 conn_state, crtc->base.id, crtc->name);
diff --git a/drivers/gpu/drm/drm_crtc_helper.c b/drivers/gpu/drm/drm_crtc_helper.c
index 79555d2..71b6c72 100644
--- a/drivers/gpu/drm/drm_crtc_helper.c
+++ b/drivers/gpu/drm/drm_crtc_helper.c
@@ -456,6 +456,9 @@ drm_crtc_helper_disable(struct drm_crtc *crtc)
 			 * between them is henceforth no longer available.
 			 */
 			connector->dpms = DRM_MODE_DPMS_OFF;
+
+			/* we keep a reference while the encoder is bound */
+			drm_connector_unreference(connector);
 		}
 	}
 
@@ -635,9 +638,12 @@ int drm_crtc_helper_set_config(struct drm_mode_set *set)
 			mode_changed = true;
 			/* If the encoder is reused for another connector, then
 			 * the appropriate crtc will be set later.
+			 * take a reference only if we haven't had an encoder before.
 			 */
 			if (connector->encoder)
 				connector->encoder->crtc = NULL;
+			else
+				drm_connector_reference(connector);
 			connector->encoder = new_encoder;
 		}
 	}
-- 
2.5.5