net/faraday: Configure old MDIO interface on Aspeed SoCs

The Aspeed SoCs have a new MDIO interface as an option in the G4 and G5
SoCs. The old one is still available, so select it in order to remain
compatible with the ftgmac100 driver.
Signed-off-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/faraday/ftgmac100.c

@@ -1252,12 +1252,21 @@ static int ftgmac100_setup_mdio(struct net_device *netdev)
 	struct ftgmac100 *priv = netdev_priv(netdev);
 	struct platform_device *pdev = to_platform_device(priv->dev);
 	int i, err = 0;
+	u32 reg;
 
 	/* initialize mdio bus */
 	priv->mii_bus = mdiobus_alloc();
 	if (!priv->mii_bus)
 		return -EIO;
 
+	if (of_machine_is_compatible("aspeed,ast2400") ||
+	    of_machine_is_compatible("aspeed,ast2500")) {
+		/* This driver supports the old MDIO interface */
+		reg = ioread32(priv->base + FTGMAC100_OFFSET_REVR);
+		reg &= ~FTGMAC100_REVR_NEW_MDIO_INTERFACE;
+		iowrite32(reg, priv->base + FTGMAC100_OFFSET_REVR);
+	};
+
 	priv->mii_bus->name = "ftgmac100_mdio";
 	snprintf(priv->mii_bus->id, MII_BUS_ID_SIZE, "%s-%d",
 		 pdev->name, pdev->id);

drivers/net/ethernet/faraday/ftgmac100.h

@@ -133,6 +133,11 @@
 #define FTGMAC100_DMAFIFOS_RXDMA_REQ		(1 << 30)
 #define FTGMAC100_DMAFIFOS_TXDMA_REQ		(1 << 31)
 
+/*
+ * Feature Register
+ */
+#define FTGMAC100_REVR_NEW_MDIO_INTERFACE	BIT(31)
+
 /*
  * Receive buffer size register
  */