diff --git a/drivers/net/dsa/mv88e6xxx/chip.c b/drivers/net/dsa/mv88e6xxx/chip.c
index 39c7ad7..e1b5c5c 100644
--- a/drivers/net/dsa/mv88e6xxx/chip.c
+++ b/drivers/net/dsa/mv88e6xxx/chip.c
@@ -2165,6 +2165,15 @@ static int mv88e6xxx_mdio_register(struct mv88e6xxx_chip *chip,
 	struct mii_bus *bus;
 	int err;
 
+	if (external) {
+		mutex_lock(&chip->reg_lock);
+		err = mv88e6xxx_g2_scratch_gpio_set_smi(chip, true);
+		mutex_unlock(&chip->reg_lock);
+
+		if (err)
+			return err;
+	}
+
 	bus = devm_mdiobus_alloc_size(chip->dev, sizeof(*mdio_bus));
 	if (!bus)
 		return -ENOMEM;
diff --git a/drivers/net/dsa/mv88e6xxx/global2.h b/drivers/net/dsa/mv88e6xxx/global2.h
index 25f92b3..d85c910 100644
--- a/drivers/net/dsa/mv88e6xxx/global2.h
+++ b/drivers/net/dsa/mv88e6xxx/global2.h
@@ -266,6 +266,11 @@
 #define MV88E6352_G2_SCRATCH_GPIO_PCTL5		0x6D
 #define MV88E6352_G2_SCRATCH_GPIO_PCTL6		0x6E
 #define MV88E6352_G2_SCRATCH_GPIO_PCTL7		0x6F
+#define MV88E6352_G2_SCRATCH_CONFIG_DATA0	0x70
+#define MV88E6352_G2_SCRATCH_CONFIG_DATA1	0x71
+#define MV88E6352_G2_SCRATCH_CONFIG_DATA1_NO_CPU	BIT(2)
+#define MV88E6352_G2_SCRATCH_CONFIG_DATA2	0x72
+#define MV88E6352_G2_SCRATCH_CONFIG_DATA2_P0_MODE_MASK	0x3
 
 #define MV88E6352_G2_SCRATCH_GPIO_PCTL_GPIO	0
 #define MV88E6352_G2_SCRATCH_GPIO_PCTL_TRIG	1
@@ -325,6 +330,9 @@ extern const struct mv88e6xxx_avb_ops mv88e6390_avb_ops;
 
 extern const struct mv88e6xxx_gpio_ops mv88e6352_gpio_ops;
 
+int mv88e6xxx_g2_scratch_gpio_set_smi(struct mv88e6xxx_chip *chip,
+				      bool external);
+
 #else /* !CONFIG_NET_DSA_MV88E6XXX_GLOBAL2 */
 
 static inline int mv88e6xxx_g2_require(struct mv88e6xxx_chip *chip)
@@ -465,6 +473,12 @@ static const struct mv88e6xxx_avb_ops mv88e6390_avb_ops = {};
 
 static const struct mv88e6xxx_gpio_ops mv88e6352_gpio_ops = {};
 
+static inline int mv88e6xxx_g2_scratch_gpio_set_smi(struct mv88e6xxx_chip *chip,
+						    bool external)
+{
+	return -EOPNOTSUPP;
+}
+
 #endif /* CONFIG_NET_DSA_MV88E6XXX_GLOBAL2 */
 
 #endif /* _MV88E6XXX_GLOBAL2_H */
diff --git a/drivers/net/dsa/mv88e6xxx/global2_scratch.c b/drivers/net/dsa/mv88e6xxx/global2_scratch.c
index 0ff12bf..3f92b88 100644
--- a/drivers/net/dsa/mv88e6xxx/global2_scratch.c
+++ b/drivers/net/dsa/mv88e6xxx/global2_scratch.c
@@ -238,3 +238,54 @@ const struct mv88e6xxx_gpio_ops mv88e6352_gpio_ops = {
 	.get_pctl = mv88e6352_g2_scratch_gpio_get_pctl,
 	.set_pctl = mv88e6352_g2_scratch_gpio_set_pctl,
 };
+
+/**
+ * mv88e6xxx_g2_gpio_set_smi - set gpio muxing for external smi
+ * @chip: chip private data
+ * @external: set mux for external smi, or free for gpio usage
+ *
+ * Some mv88e6xxx models have GPIO pins that may be configured as
+ * an external SMI interface, or they may be made free for other
+ * GPIO uses.
+ */
+int mv88e6xxx_g2_scratch_gpio_set_smi(struct mv88e6xxx_chip *chip,
+				      bool external)
+{
+	int misc_cfg = MV88E6352_G2_SCRATCH_MISC_CFG;
+	int config_data1 = MV88E6352_G2_SCRATCH_CONFIG_DATA1;
+	int config_data2 = MV88E6352_G2_SCRATCH_CONFIG_DATA2;
+	bool no_cpu;
+	u8 p0_mode;
+	int err;
+	u8 val;
+
+	err = mv88e6xxx_g2_scratch_read(chip, config_data2, &val);
+	if (err)
+		return err;
+
+	p0_mode = val & MV88E6352_G2_SCRATCH_CONFIG_DATA2_P0_MODE_MASK;
+
+	if (p0_mode == 0x01 || p0_mode == 0x02)
+		return -EBUSY;
+
+	err = mv88e6xxx_g2_scratch_read(chip, config_data1, &val);
+	if (err)
+		return err;
+
+	no_cpu = !!(val & MV88E6352_G2_SCRATCH_CONFIG_DATA1_NO_CPU);
+
+	err = mv88e6xxx_g2_scratch_read(chip, misc_cfg, &val);
+	if (err)
+		return err;
+
+	/* NO_CPU being 0 inverts the meaning of the bit */
+	if (!no_cpu)
+		external = !external;
+
+	if (external)
+		val |= MV88E6352_G2_SCRATCH_MISC_CFG_NORMALSMI;
+	else
+		val &= ~MV88E6352_G2_SCRATCH_MISC_CFG_NORMALSMI;
+
+	return mv88e6xxx_g2_scratch_write(chip, misc_cfg, val);
+}