net: dsa: microchip: ksz8795: Fix VLAN filtering

[ Upstream commit 1648441 ]

Currently ksz8_port_vlan_filtering() sets or clears the VLAN Enable
hardware flag.  That controls discarding of packets with a VID that
has not been enabled for any port on the switch.

Since it is a global flag, set the dsa_switch::vlan_filtering_is_global
flag so that the DSA core understands this can't be controlled per
port.

When VLAN filtering is enabled, the switch should also discard packets
with a VID that's not enabled on the ingress port.  Set or clear each
external port's VLAN Ingress Filter flag in ksz8_port_vlan_filtering()
to make that happen.

Fixes: e66f840 ("net: dsa: ksz: Add Microchip KSZ8795 DSA driver")
Signed-off-by: Ben Hutchings <ben.hutchings@mind.be>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/net/dsa/microchip/ksz8795.c

@@ -790,8 +790,14 @@ static int ksz8795_port_vlan_filtering(struct dsa_switch *ds, int port,
 	if (switchdev_trans_ph_prepare(trans))
 		return 0;
 
+	/* Discard packets with VID not enabled on the switch */
 	ksz_cfg(dev, S_MIRROR_CTRL, SW_VLAN_ENABLE, flag);
 
+	/* Discard packets with VID not enabled on the ingress port */
+	for (port = 0; port < dev->phy_port_cnt; ++port)
+		ksz_port_cfg(dev, port, REG_PORT_CTRL_2, PORT_INGRESS_FILTER,
+			     flag);
+
 	return 0;
 }
 
@@ -1266,6 +1272,11 @@ static int ksz8795_switch_init(struct ksz_device *dev)
 	/* set the real number of ports */
 	dev->ds->num_ports = dev->port_cnt + 1;
 
+	/* VLAN filtering is partly controlled by the global VLAN
+	 * Enable flag
+	 */
+	dev->ds->vlan_filtering_is_global = true;
+
 	return 0;
 }