net: dsa: mt7530: fix tagged frames pass-through in VLAN-unaware mode

In VLAN-unaware mode, the Egress Tag (EG_TAG) field in Port VLAN
Control register must be set to Consistent to let tagged frames pass
through as is, otherwise their tags will be stripped.

Fixes: 83163f7 ("net: dsa: mediatek: add VLAN support for MT7530")
Signed-off-by: DENG Qingfang <dqfext@gmail.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Tested-by: René van Dorst <opensource@vdorst.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/mt7530.c

@@ -773,8 +773,9 @@ mt7530_port_set_vlan_unaware(struct dsa_switch *ds, int port)
 	 */
 	mt7530_rmw(priv, MT7530_PCR_P(port), PCR_PORT_VLAN_MASK,
 		   MT7530_PORT_MATRIX_MODE);
-	mt7530_rmw(priv, MT7530_PVC_P(port), VLAN_ATTR_MASK,
-		   VLAN_ATTR(MT7530_VLAN_TRANSPARENT));
+	mt7530_rmw(priv, MT7530_PVC_P(port), VLAN_ATTR_MASK | PVC_EG_TAG_MASK,
+		   VLAN_ATTR(MT7530_VLAN_TRANSPARENT) |
+		   PVC_EG_TAG(MT7530_VLAN_EG_CONSISTENT));
 
 	for (i = 0; i < MT7530_NUM_PORTS; i++) {
 		if (dsa_is_user_port(ds, i) &&
@@ -790,8 +791,8 @@ mt7530_port_set_vlan_unaware(struct dsa_switch *ds, int port)
 	if (all_user_ports_removed) {
 		mt7530_write(priv, MT7530_PCR_P(MT7530_CPU_PORT),
 			     PCR_MATRIX(dsa_user_ports(priv->ds)));
-		mt7530_write(priv, MT7530_PVC_P(MT7530_CPU_PORT),
-			     PORT_SPEC_TAG);
+		mt7530_write(priv, MT7530_PVC_P(MT7530_CPU_PORT), PORT_SPEC_TAG
+			     | PVC_EG_TAG(MT7530_VLAN_EG_CONSISTENT));
 	}
 }
 
@@ -817,8 +818,9 @@ mt7530_port_set_vlan_aware(struct dsa_switch *ds, int port)
 	/* Set the port as a user port which is to be able to recognize VID
 	 * from incoming packets before fetching entry within the VLAN table.
 	 */
-	mt7530_rmw(priv, MT7530_PVC_P(port), VLAN_ATTR_MASK,
-		   VLAN_ATTR(MT7530_VLAN_USER));
+	mt7530_rmw(priv, MT7530_PVC_P(port), VLAN_ATTR_MASK | PVC_EG_TAG_MASK,
+		   VLAN_ATTR(MT7530_VLAN_USER) |
+		   PVC_EG_TAG(MT7530_VLAN_EG_DISABLED));
 }
 
 static void
@@ -1303,6 +1305,10 @@ mt7530_setup(struct dsa_switch *ds)
 			mt7530_cpu_port_enable(priv, i);
 		else
 			mt7530_port_disable(ds, i);
+
+		/* Enable consistent egress tag */
+		mt7530_rmw(priv, MT7530_PVC_P(i), PVC_EG_TAG_MASK,
+			   PVC_EG_TAG(MT7530_VLAN_EG_CONSISTENT));
 	}
 
 	/* Setup port 5 */

drivers/net/dsa/mt7530.h

@@ -172,9 +172,16 @@ enum mt7530_port_mode {
 /* Register for port vlan control */
 #define MT7530_PVC_P(x)			(0x2010 + ((x) * 0x100))
 #define  PORT_SPEC_TAG			BIT(5)
+#define  PVC_EG_TAG(x)			(((x) & 0x7) << 8)
+#define  PVC_EG_TAG_MASK		PVC_EG_TAG(7)
 #define  VLAN_ATTR(x)			(((x) & 0x3) << 6)
 #define  VLAN_ATTR_MASK			VLAN_ATTR(3)
 
+enum mt7530_vlan_port_eg_tag {
+	MT7530_VLAN_EG_DISABLED = 0,
+	MT7530_VLAN_EG_CONSISTENT = 1,
+};
+
 enum mt7530_vlan_port_attr {
 	MT7530_VLAN_USER = 0,
 	MT7530_VLAN_TRANSPARENT = 3,