diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
index ebfefdd8e04f1..3c916ac301905 100644
--- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
+++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
@@ -64,7 +64,7 @@
 #define KEEPALIVE_VER 1
 #define KEEPALIVE_VER_MIN KEEPALIVE_VER
 
-DEFINE_SPINLOCK(msg_queue_spinlock); /* FIXME */
+DEFINE_SPINLOCK(msg_queue_spinlock); /* serialise access to the message queues to userspace */
 struct vchiq_state g_state;
 
 static struct platform_device *bcm2835_camera;
diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.c
index 3c0fcd9adf752..200f7e25ac8af 100644
--- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.c
+++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.c
@@ -149,8 +149,8 @@ static inline void check_sizes(void)
 	BUILD_BUG_ON_NOT_POWER_OF_2(VCHIQ_MAX_SERVICES);
 }
 
-DEFINE_SPINLOCK(bulk_waiter_spinlock); /* FIXME */
-static DEFINE_SPINLOCK(quota_spinlock); /* FIXME */
+DEFINE_SPINLOCK(bulk_waiter_spinlock); /* serialiase completion of blocking transfers */
+static DEFINE_SPINLOCK(quota_spinlock); /* serialise updates to slot quota data */
 
 static unsigned int handle_seq;
 
diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.h b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.h
index f78c9554d0f2c..35165e7ff18e5 100644
--- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.h
+++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_core.h
@@ -195,7 +195,7 @@ struct vchiq_service {
 
 	struct completion remove_event;
 	struct completion bulk_remove_event;
-	struct mutex bulk_mutex; /* FIXME */
+	struct mutex bulk_mutex; /* serialise access to the bulk transfer queues */
 
 	struct service_stats_struct {
 		int quota_stalls;
@@ -312,7 +312,7 @@ struct vchiq_state {
 	struct completion connect;
 
 	/* Mutex protecting services */
-	struct mutex mutex; /* FIXME */
+	struct mutex mutex; /* serialise service creation */
 	struct vchiq_instance **instance;
 
 	/* Processes incoming messages */
@@ -340,13 +340,13 @@ struct vchiq_state {
 	char *rx_data;
 	struct vchiq_slot_info *rx_info;
 
-	struct mutex slot_mutex; /* FIXME */
+	struct mutex slot_mutex; /* serialise access to the main message slots */
 
-	struct mutex recycle_mutex; /* FIXME */
+	struct mutex recycle_mutex; /* serialise slot refcount updates */
 
-	struct mutex sync_mutex; /* FIXME */
+	struct mutex sync_mutex; /* serialise access to the single synchronous message slot */
 
-	struct mutex bulk_transfer_mutex; /* FIXME */
+	struct mutex bulk_transfer_mutex; /* Unused, following upstream changes */
 
 	/*
 	 * Indicates the byte position within the stream from where the next