net: ks8851: Register MDIO bus and the internal PHY

The KS8851 has a reduced internal PHY, which is accessible through its
registers at offset 0xe4. The PHY is compatible with KS886x PHY present
in Micrel switches, except the PHY ID Low/High registers are swapped.
Register MDIO bus so this PHY can be detected and probed by phylib.

Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Andrew Lunn <andrew@lunn.ch>
Cc: Heiner Kallweit <hkallweit1@gmail.com>
Cc: Lukas Wunner <lukas@wunner.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/micrel/ks8851.h

@@ -358,6 +358,7 @@ union ks8851_tx_hdr {
  * @vdd_reg:	Optional regulator supplying the chip
  * @vdd_io: Optional digital power supply for IO
  * @gpio: Optional reset_n gpio
+ * @mii_bus: Pointer to MII bus structure
  * @lock: Bus access lock callback
  * @unlock: Bus access unlock callback
  * @rdreg16: 16bit register read callback
@@ -403,6 +404,7 @@ struct ks8851_net {
 	struct regulator	*vdd_reg;
 	struct regulator	*vdd_io;
 	int			gpio;
+	struct mii_bus		*mii_bus;
 
 	void			(*lock)(struct ks8851_net *ks,
 					unsigned long *flags);

drivers/net/ethernet/micrel/ks8851_common.c

@@ -23,6 +23,7 @@
 
 #include <linux/gpio.h>
 #include <linux/of_gpio.h>
+#include <linux/of_mdio.h>
 #include <linux/of_net.h>
 
 #include "ks8851.h"
@@ -932,7 +933,25 @@ static int ks8851_phy_reg(int reg)
 		return KS_P1ANLPR;
 	}
 
-	return 0x0;
+	return -EOPNOTSUPP;
+}
+
+static int ks8851_phy_read_common(struct net_device *dev, int phy_addr, int reg)
+{
+	struct ks8851_net *ks = netdev_priv(dev);
+	unsigned long flags;
+	int result;
+	int ksreg;
+
+	ksreg = ks8851_phy_reg(reg);
+	if (ksreg < 0)
+		return ksreg;
+
+	ks8851_lock(ks, &flags);
+	result = ks8851_rdreg16(ks, ksreg);
+	ks8851_unlock(ks, &flags);
+
+	return result;
 }
 
 /**
@@ -952,20 +971,13 @@ static int ks8851_phy_reg(int reg)
  */
 static int ks8851_phy_read(struct net_device *dev, int phy_addr, int reg)
 {
-	struct ks8851_net *ks = netdev_priv(dev);
+	int ret;
-	unsigned long flags;
-	int ksreg;
-	int result;
 
-	ksreg = ks8851_phy_reg(reg);
+	ret = ks8851_phy_read_common(dev, phy_addr, reg);
-	if (!ksreg)
+	if (ret < 0)
 		return 0x0;	/* no error return allowed, so use zero */
 
-	ks8851_lock(ks, &flags);
+	return ret;
-	result = ks8851_rdreg16(ks, ksreg);
-	ks8851_unlock(ks, &flags);
-
-	return result;
 }
 
 static void ks8851_phy_write(struct net_device *dev,
@@ -976,13 +988,37 @@ static void ks8851_phy_write(struct net_device *dev,
 	int ksreg;
 
 	ksreg = ks8851_phy_reg(reg);
-	if (ksreg) {
+	if (ksreg >= 0) {
 		ks8851_lock(ks, &flags);
 		ks8851_wrreg16(ks, ksreg, value);
 		ks8851_unlock(ks, &flags);
 	}
 }
 
+static int ks8851_mdio_read(struct mii_bus *bus, int phy_id, int reg)
+{
+	struct ks8851_net *ks = bus->priv;
+
+	if (phy_id != 0)
+		return -EOPNOTSUPP;
+
+	/* KS8851 PHY ID registers are swapped in HW, swap them back. */
+	if (reg == MII_PHYSID1)
+		reg = MII_PHYSID2;
+	else if (reg == MII_PHYSID2)
+		reg = MII_PHYSID1;
+
+	return ks8851_phy_read_common(ks->netdev, phy_id, reg);
+}
+
+static int ks8851_mdio_write(struct mii_bus *bus, int phy_id, int reg, u16 val)
+{
+	struct ks8851_net *ks = bus->priv;
+
+	ks8851_phy_write(ks->netdev, phy_id, reg, val);
+	return 0;
+}
+
 /**
  * ks8851_read_selftest - read the selftest memory info.
  * @ks: The device state
@@ -1046,6 +1082,42 @@ int ks8851_resume(struct device *dev)
 }
 #endif
 
+static int ks8851_register_mdiobus(struct ks8851_net *ks, struct device *dev)
+{
+	struct mii_bus *mii_bus;
+	int ret;
+
+	mii_bus = mdiobus_alloc();
+	if (!mii_bus)
+		return -ENOMEM;
+
+	mii_bus->name = "ks8851_eth_mii";
+	mii_bus->read = ks8851_mdio_read;
+	mii_bus->write = ks8851_mdio_write;
+	mii_bus->priv = ks;
+	mii_bus->parent = dev;
+	mii_bus->phy_mask = ~((u32)BIT(0));
+	snprintf(mii_bus->id, MII_BUS_ID_SIZE, "%s", dev_name(dev));
+
+	ret = mdiobus_register(mii_bus);
+	if (ret)
+		goto err_mdiobus_register;
+
+	ks->mii_bus = mii_bus;
+
+	return 0;
+
+err_mdiobus_register:
+	mdiobus_free(mii_bus);
+	return ret;
+}
+
+static void ks8851_unregister_mdiobus(struct ks8851_net *ks)
+{
+	mdiobus_unregister(ks->mii_bus);
+	mdiobus_free(ks->mii_bus);
+}
+
 int ks8851_probe_common(struct net_device *netdev, struct device *dev,
 			int msg_en)
 {
@@ -1104,6 +1176,8 @@ int ks8851_probe_common(struct net_device *netdev, struct device *dev,
 
 	INIT_WORK(&ks->rxctrl_work, ks8851_rxctrl_work);
 
+	SET_NETDEV_DEV(netdev, dev);
+
 	/* setup EEPROM state */
 	ks->eeprom.data = ks;
 	ks->eeprom.width = PCI_EEPROM_WIDTH_93C46;
@@ -1120,6 +1194,10 @@ int ks8851_probe_common(struct net_device *netdev, struct device *dev,
 
 	dev_info(dev, "message enable is %d\n", msg_en);
 
+	ret = ks8851_register_mdiobus(ks, dev);
+	if (ret)
+		goto err_mdio;
+
 	/* set the default message enable */
 	ks->msg_enable = netif_msg_init(msg_en, NETIF_MSG_DRV |
 						NETIF_MSG_PROBE |
@@ -1128,7 +1206,6 @@ int ks8851_probe_common(struct net_device *netdev, struct device *dev,
 	skb_queue_head_init(&ks->txq);
 
 	netdev->ethtool_ops = &ks8851_ethtool_ops;
-	SET_NETDEV_DEV(netdev, dev);
 
 	dev_set_drvdata(dev, ks);
 
@@ -1156,7 +1233,7 @@ int ks8851_probe_common(struct net_device *netdev, struct device *dev,
 	ret = register_netdev(netdev);
 	if (ret) {
 		dev_err(dev, "failed to register network device\n");
-		goto err_netdev;
+		goto err_id;
 	}
 
 	netdev_info(netdev, "revision %d, MAC %pM, IRQ %d, %s EEPROM\n",
@@ -1165,8 +1242,9 @@ int ks8851_probe_common(struct net_device *netdev, struct device *dev,
 
 	return 0;
 
-err_netdev:
 err_id:
+	ks8851_unregister_mdiobus(ks);
+err_mdio:
 	if (gpio_is_valid(gpio))
 		gpio_set_value(gpio, 0);
 	regulator_disable(ks->vdd_reg);
@@ -1180,6 +1258,8 @@ int ks8851_remove_common(struct device *dev)
 {
 	struct ks8851_net *priv = dev_get_drvdata(dev);
 
+	ks8851_unregister_mdiobus(priv);
+
 	if (netif_msg_drv(priv))
 		dev_info(dev, "remove\n");