net: mscc: ocelot: don't hardcode the number of the CPU port

VSC7514 is a 10-port switch with 2 extra "CPU ports" (targets in the
queuing subsystem for terminating traffic locally).

There are 2 issues with hardcoding the CPU port as #10:
- It is not clear which snippets of the code are configuring something
  for one of the CPU ports, and which snippets are just doing something
  related to the number of physical ports.
- Actually any physical port can act as a CPU port connected to an
  external CPU (in addition to the local CPU). This is called NPI mode
  (Node Processor Interface) and is the way that the 6-port VSC9959
  (Felix) switch is integrated inside NXP LS1028A (the "local management
  CPU" functionality is not used there).

This patch makes it clear that the ocelot_bridge_stp_state_set function
operates on the CPU port (by making it an implicit member of the
bridging domain), and at the same time adds logic for the NPI port (aka
a physical port) to play the role of a CPU port (it shouldn't be part of
bridge_fwd_mask, as it's not explicitly enslaved to a bridge).
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mscc/ocelot.c

@@ -1383,7 +1383,7 @@ static void ocelot_bridge_stp_state_set(struct ocelot *ocelot, int port,
 	 * a source for the other ports.
 	 */
 	for (p = 0; p < ocelot->num_phys_ports; p++) {
-		if (ocelot->bridge_fwd_mask & BIT(p)) {
+		if (p == ocelot->cpu || (ocelot->bridge_fwd_mask & BIT(p))) {
 			unsigned long mask = ocelot->bridge_fwd_mask & ~BIT(p);
 
 			for (i = 0; i < ocelot->num_phys_ports; i++) {
@@ -1398,15 +1398,18 @@ static void ocelot_bridge_stp_state_set(struct ocelot *ocelot, int port,
 				}
 			}
 
-			ocelot_write_rix(ocelot,
-					 BIT(ocelot->num_phys_ports) | mask,
+			/* Avoid the NPI port from looping back to itself */
+			if (p != ocelot->cpu)
+				mask |= BIT(ocelot->cpu);
+
+			ocelot_write_rix(ocelot, mask,
 					 ANA_PGID_PGID, PGID_SRC + p);
 		} else {
 			/* Only the CPU port, this is compatible with link
 			 * aggregation.
 			 */
 			ocelot_write_rix(ocelot,
-					 BIT(ocelot->num_phys_ports),
+					 BIT(ocelot->cpu),
 					 ANA_PGID_PGID, PGID_SRC + p);
 		}
 	}