diff --git a/target/linux/generic/files/drivers/net/phy/ar8216.c b/target/linux/generic/files/drivers/net/phy/ar8216.c
index 1521ea317..c199ac178 100644
--- a/target/linux/generic/files/drivers/net/phy/ar8216.c
+++ b/target/linux/generic/files/drivers/net/phy/ar8216.c
@@ -29,6 +29,7 @@
 #include <linux/phy.h>
 #include <linux/netdevice.h>
 #include <linux/etherdevice.h>
+#include <linux/lockdep.h>
 #include "ar8216.h"
 
 /* size of the vlan table */
@@ -122,6 +123,8 @@ ar8216_rmw(struct ar8216_priv *priv, int reg, u32 mask, u32 val)
 {
 	u32 v;
 
+	lockdep_assert_held(&priv->reg_mutex);
+
 	v = priv->read(priv, reg);
 	v &= ~mask;
 	v |= val;