mlxsw: spectrum: Don't forward packets when STP state is DISABLED

When STP state is set to DISABLED the port is assumed to be inactive, but
currently we forward packets ingressing through it.

Instead, set the port's STP state in hardware to DISCARDING, which means
it doesn't forward packets or perform any learning, but it does trap
control packets. However, these packets will be dropped by bridge code,
which results in the expected behavior.

Fixes: 56ade8fe3f ("mlxsw: spectrum: Add initial support for Spectrum ASIC")
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlxsw/spectrum_switchdev.c

@@ -124,7 +124,6 @@ static int mlxsw_sp_port_stp_state_set(struct mlxsw_sp_port *mlxsw_sp_port,
 	int err;
 
 	switch (state) {
-	case BR_STATE_DISABLED: /* fall-through */
 	case BR_STATE_FORWARDING:
 		spms_state = MLXSW_REG_SPMS_STATE_FORWARDING;
 		break;
@@ -132,6 +131,7 @@ static int mlxsw_sp_port_stp_state_set(struct mlxsw_sp_port *mlxsw_sp_port,
 	case BR_STATE_LEARNING:
 		spms_state = MLXSW_REG_SPMS_STATE_LEARNING;
 		break;
+	case BR_STATE_DISABLED: /* fall-through */
 	case BR_STATE_BLOCKING:
 		spms_state = MLXSW_REG_SPMS_STATE_DISCARDING;
 		break;