net: dsa: mv88e6xxx: scratch registers and external MDIO pins

MV88E6352 and later switches support GPIO control through the "Scratch
& Misc" global2 register. Two of the pins controlled this way on the
mv88e6390 family are the external MDIO pins. They can either by used
as part of the MII interface for port 0, GPIOs, or MDIO. Add a
function to configure them for MDIO, if possible, and call it when
registering the external MDIO bus.
Suggested-by: Russell King <rmk@armlinux.org.uk>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

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;

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 */

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);
+}