diff --git a/sys/dev/isci/isci.h b/sys/dev/isci/isci.h
index 66a0330c4bd..70ba16afd3c 100644
--- a/sys/dev/isci/isci.h
+++ b/sys/dev/isci/isci.h
@@ -122,6 +122,7 @@ struct ISCI_CONTROLLER
 	SCI_CONTROLLER_HANDLE_T	scif_controller_handle;
 	struct ISCI_DOMAIN	domain[SCI_MAX_DOMAINS];
 	BOOL			is_started;
+	BOOL			has_been_scanned;
 	uint32_t		initial_discovery_mask;
 	BOOL			is_frozen;
 	uint8_t			*remote_device_memory;
diff --git a/sys/dev/isci/isci_controller.c b/sys/dev/isci/isci_controller.c
index f2409289e4b..38d91acec7d 100644
--- a/sys/dev/isci/isci_controller.c
+++ b/sys/dev/isci/isci_controller.c
@@ -36,6 +36,9 @@ __FBSDID("$FreeBSD$");
 #include <sys/conf.h>
 #include <sys/malloc.h>
 
+#include <cam/cam_periph.h>
+#include <cam/cam_xpt_periph.h>
+
 #include <dev/isci/scil/sci_memory_descriptor_list.h>
 #include <dev/isci/scil/sci_memory_descriptor_list_decorator.h>
 
@@ -300,6 +303,16 @@ SCI_STATUS isci_controller_initialize(struct ISCI_CONTROLLER *controller)
 	TUNABLE_INT_FETCH("hw.isci.io_shortage", &io_shortage);
 	controller->sim_queue_depth += io_shortage;
 
+	/* Attach to CAM using xpt_bus_register now, then immediately freeze
+	 *  the simq.  It will get released later when initial domain discovery
+	 *  is complete.
+	 */
+	controller->has_been_scanned = FALSE;
+	mtx_lock(&controller->lock);
+	isci_controller_attach_to_cam(controller);
+	xpt_freeze_simq(controller->sim, 1);
+	mtx_unlock(&controller->lock);
+
 	return (scif_controller_initialize(controller->scif_controller_handle));
 }
 
@@ -441,13 +454,13 @@ void isci_controller_start(void *controller_handle)
 void isci_controller_domain_discovery_complete(
     struct ISCI_CONTROLLER *isci_controller, struct ISCI_DOMAIN *isci_domain)
 {
-	if (isci_controller->sim == NULL)
+	if (!isci_controller->has_been_scanned)
 	{
-		/* Controller has not been attached to CAM yet.  We'll clear
+		/* Controller has not been scanned yet.  We'll clear
 		 *  the discovery bit for this domain, then check if all bits
 		 *  are now clear.  That would indicate that all domains are
-		 *  done with discovery and we can then attach the controller
-		 *  to CAM.
+		 *  done with discovery and we can then proceed with initial
+		 *  scan.
 		 */
 
 		isci_controller->initial_discovery_mask &=
@@ -457,7 +470,25 @@ void isci_controller_domain_discovery_complete(
 			struct isci_softc *driver = isci_controller->isci;
 			uint8_t next_index = isci_controller->index + 1;
 
-			isci_controller_attach_to_cam(isci_controller);
+			isci_controller->has_been_scanned = TRUE;
+
+			/* Unfreeze simq to allow initial scan to proceed. */
+			xpt_release_simq(isci_controller->sim, TRUE);
+
+#if __FreeBSD_version < 800000
+			/* When driver is loaded after boot, we need to
+			 *  explicitly rescan here for versions <8.0, because
+			 *  CAM only automatically scans new buses at boot
+			 *  time.
+			 */
+			union ccb *ccb = xpt_alloc_ccb_nowait();
+
+			xpt_create_path(&ccb->ccb_h.path, xpt_periph,
+			    cam_sim_path(isci_controller->sim),
+			    CAM_TARGET_WILDCARD, CAM_LUN_WILDCARD);
+
+			xpt_rescan(ccb);
+#endif
 
 			if (next_index < driver->controller_count) {
 				/*  There are more controllers that need to
diff --git a/sys/dev/isci/isci_remote_device.c b/sys/dev/isci/isci_remote_device.c
index 2388dae39ba..d22b4d4abff 100644
--- a/sys/dev/isci/isci_remote_device.c
+++ b/sys/dev/isci/isci_remote_device.c
@@ -74,13 +74,12 @@ scif_cb_remote_device_ready(SCI_CONTROLLER_HANDLE_T controller,
 		isci_controller->remote_device[device_index] =
 		    isci_remote_device;
 
-		if (isci_controller->sim != NULL) {
-			/* The sim object is not NULL, meaning we have attached
-			 *  the controller to CAM already.  In that case, create
-			 *  a CCB to instruct CAM to rescan this device.
-			 * If the sim object is NULL, this device will get
-			 *  scanned as part of the initial scan when the
-			 *  controller is attached to CAM.
+		if (isci_controller->has_been_scanned) {
+			/* The sim object has been scanned at least once
+			 *  already.  In that case, create a CCB to instruct
+			 *  CAM to rescan this device.
+			 * If the sim object has not been scanned, this device
+			 *  will get scanned as part of the initial scan.
 			 */
 			union ccb *ccb = xpt_alloc_ccb_nowait();