net: dsa: tag_8021q: Change order of rx_vid setup

The 802.1Q tagging performs an unbalanced setup in terms of RX VIDs on
the CPU port. For the ingress path of a 802.1Q switch to work, the RX
VID of a port needs to be seen as tagged egress on the CPU port.

While configuring the other front-panel ports to be part of this VID,
for bridge scenarios, the untagged flag is applied even on the CPU port
in dsa_switch_vlan_add.  This happens because DSA applies the same flags
on the CPU port as on the (bridge-controlled) slave ports, and the
effect in this case is that the CPU port tagged settings get deleted.

Instead of fixing DSA by introducing a way to control VLAN flags on the
CPU port (and hence stop inheriting from the slave ports) - a hard,
perhaps intractable problem - avoid this situation by moving the setup
part of the RX VID on the CPU port after all the other front-panel ports
have been added to the VID.

Fixes: f9bbe44 ("net: dsa: Optional VLAN-based port separation for switches without tagging")
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/dsa/tag_8021q.c

@@ -128,10 +128,7 @@ int dsa_port_setup_8021q_tagging(struct dsa_switch *ds, int port, bool enabled)
 		u16 flags;
 
 		if (i == upstream)
-			/* CPU port needs to see this port's RX VID
-			 * as tagged egress.
-			 */
-			flags = 0;
+			continue;
 		else if (i == port)
 			/* The RX VID is pvid on this port */
 			flags = BRIDGE_VLAN_INFO_UNTAGGED |
@@ -150,6 +147,20 @@ int dsa_port_setup_8021q_tagging(struct dsa_switch *ds, int port, bool enabled)
 			return err;
 		}
 	}
+
+	/* CPU port needs to see this port's RX VID
+	 * as tagged egress.
+	 */
+	if (enabled)
+		err = dsa_port_vid_add(upstream_dp, rx_vid, 0);
+	else
+		err = dsa_port_vid_del(upstream_dp, rx_vid);
+	if (err) {
+		dev_err(ds->dev, "Failed to apply RX VID %d to port %d: %d\n",
+			rx_vid, port, err);
+		return err;
+	}
+
 	/* Finally apply the TX VID on this port and on the CPU port */
 	if (enabled)
 		err = dsa_port_vid_add(dp, tx_vid, BRIDGE_VLAN_INFO_UNTAGGED);