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>

1 files changed, 51 insertions, 0 deletions

diff --git a/drivers/net/dsa/mv88e6xxx/global2_scratch.c b/drivers/net/dsa/mv88e6xxx/global2_scratch.c
index 0ff12bff9f0e..3f92b8892dc7 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);
+}