net: dsa: better error reporting

Add additional error reporting to the generic DSA code, so it's easier
to debug when things go wrong.  This was useful when initially bringing
up 88e6176 on a new board.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Acked-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/dsa/dsa.c

@@ -326,8 +326,8 @@ static int dsa_switch_setup_one(struct dsa_switch *ds, struct device *parent)
 
 		ret = dsa_slave_create(ds, parent, i, pd->port_names[i]);
 		if (ret < 0) {
-			netdev_err(dst->master_netdev, "[%d]: can't create dsa slave device for port %d(%s)\n",
-				   index, i, pd->port_names[i]);
+			netdev_err(dst->master_netdev, "[%d]: can't create dsa slave device for port %d(%s): %d\n",
+				   index, i, pd->port_names[i], ret);
 			ret = 0;
 		}
 	}

net/dsa/slave.c

@@ -1026,8 +1026,10 @@ static int dsa_slave_phy_connect(struct dsa_slave_priv *p,
 	struct dsa_switch *ds = p->parent;
 
 	p->phy = ds->slave_mii_bus->phy_map[addr];
-	if (!p->phy)
+	if (!p->phy) {
+		netdev_err(slave_dev, "no phy at %d\n", addr);
 		return -ENODEV;
+	}
 
 	/* Use already configured phy mode */
 	if (p->phy_interface == PHY_INTERFACE_MODE_NA)
@@ -1061,7 +1063,7 @@ static int dsa_slave_phy_setup(struct dsa_slave_priv *p,
 		 */
 		ret = of_phy_register_fixed_link(port_dn);
 		if (ret) {
-			netdev_err(slave_dev, "failed to register fixed PHY\n");
+			netdev_err(slave_dev, "failed to register fixed PHY: %d\n", ret);
 			return ret;
 		}
 		phy_is_fixed = true;
@@ -1072,17 +1074,20 @@ static int dsa_slave_phy_setup(struct dsa_slave_priv *p,
 		phy_flags = ds->drv->get_phy_flags(ds, p->port);
 
 	if (phy_dn) {
-		ret = of_mdio_parse_addr(&slave_dev->dev, phy_dn);
+		int phy_id = of_mdio_parse_addr(&slave_dev->dev, phy_dn);
+
 		/* If this PHY address is part of phys_mii_mask, which means
 		 * that we need to divert reads and writes to/from it, then we
 		 * want to bind this device using the slave MII bus created by
 		 * DSA to make that happen.
 		 */
-		if (!phy_is_fixed && ret >= 0 &&
-		    (ds->phys_mii_mask & (1 << ret))) {
-			ret = dsa_slave_phy_connect(p, slave_dev, ret);
-			if (ret)
+		if (!phy_is_fixed && phy_id >= 0 &&
+		    (ds->phys_mii_mask & (1 << phy_id))) {
+			ret = dsa_slave_phy_connect(p, slave_dev, phy_id);
+			if (ret) {
+				netdev_err(slave_dev, "failed to connect to phy%d: %d\n", phy_id, ret);
 				return ret;
+			}
 		} else {
 			p->phy = of_phy_connect(slave_dev, phy_dn,
 						dsa_slave_adjust_link,
@@ -1099,8 +1104,10 @@ static int dsa_slave_phy_setup(struct dsa_slave_priv *p,
 	 */
 	if (!p->phy) {
 		ret = dsa_slave_phy_connect(p, slave_dev, p->port);
-		if (ret)
+		if (ret) {
+			netdev_err(slave_dev, "failed to connect to port %d: %d\n", p->port, ret);
 			return ret;
+		}
 	} else {
 		netdev_info(slave_dev, "attached PHY at address %d [%s]\n",
 			    p->phy->addr, p->phy->drv->name);
@@ -1212,6 +1219,7 @@ int dsa_slave_create(struct dsa_switch *ds, struct device *parent,
 
 	ret = dsa_slave_phy_setup(p, slave_dev);
 	if (ret) {
+		netdev_err(master, "error %d setting up slave phy\n", ret);
 		free_netdev(slave_dev);
 		return ret;
 	}