net: lan966x: Fix assignment of the MAC address

The following two scenarios were failing for lan966x.
1. If the port had the address X and then trying to assign the same
   address, then the HW was just removing this address because first it
   tries to learn new address and then delete the old one. As they are
   the same the HW remove it.
2. If the port eth0 was assigned the same address as one of the other
   ports eth1 then when assigning back the address to eth0 then the HW
   was deleting the address of eth1.

The case 1. is fixed by checking if the port has already the same
address while case 2. is fixed by checking if the address is used by any
other port.

Fixes: e18aba89 ("net: lan966x: add mactable support")
Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Link: https://lore.kernel.org/r/20220513180030.3076793-1-horatiu.vultur@microchip.comSigned-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/ethernet/microchip/lan966x/lan966x_main.c

@@ -103,6 +103,24 @@ static int lan966x_create_targets(struct platform_device *pdev,
 	return 0;
 }
 
+static bool lan966x_port_unique_address(struct net_device *dev)
+{
+	struct lan966x_port *port = netdev_priv(dev);
+	struct lan966x *lan966x = port->lan966x;
+	int p;
+
+	for (p = 0; p < lan966x->num_phys_ports; ++p) {
+		port = lan966x->ports[p];
+		if (!port || port->dev == dev)
+			continue;
+
+		if (ether_addr_equal(dev->dev_addr, port->dev->dev_addr))
+			return false;
+	}
+
+	return true;
+}
+
 static int lan966x_port_set_mac_address(struct net_device *dev, void *p)
 {
 	struct lan966x_port *port = netdev_priv(dev);
@@ -110,16 +128,26 @@ static int lan966x_port_set_mac_address(struct net_device *dev, void *p)
 	const struct sockaddr *addr = p;
 	int ret;
 
+	if (ether_addr_equal(addr->sa_data, dev->dev_addr))
+		return 0;
+
 	/* Learn the new net device MAC address in the mac table. */
 	ret = lan966x_mac_cpu_learn(lan966x, addr->sa_data, HOST_PVID);
 	if (ret)
 		return ret;
 
+	/* If there is another port with the same address as the dev, then don't
+	 * delete it from the MAC table
+	 */
+	if (!lan966x_port_unique_address(dev))
+		goto out;
+
 	/* Then forget the previous one. */
 	ret = lan966x_mac_cpu_forget(lan966x, dev->dev_addr, HOST_PVID);
 	if (ret)
 		return ret;
 
+out:
 	eth_hw_addr_set(dev, addr->sa_data);
 	return ret;
 }