net: dsa: vsc73xx: Implement the tag_8021q VLAN operations

This patch is a simple implementation of 802.1q tagging in the vsc73xx
driver. Currently, devices with DSA_TAG_PROTO_NONE are not functional.
The VSC73XX family doesn't provide any tag support for external Ethernet
ports.

The only option available is VLAN-based tagging, which requires constant
hardware VLAN filtering. While the VSC73XX family supports provider
bridging, it only supports QinQ without full implementation of 802.1AD.
This means it only allows the doubled 0x8100 TPID.

In the simple port mode, QinQ is enabled to preserve forwarding of
VLAN-tagged frames.
Signed-off-by: Pawel Dembicki <paweldembicki@gmail.com>
Reviewed-by: Vladimir Oltean <olteanv@gmail.com>
Link: https://patch.msgid.link/20240713211620.1125910-9-paweldembicki@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

drivers/net/dsa/Kconfig

@@ -127,7 +127,7 @@ config NET_DSA_SMSC_LAN9303_MDIO
 
 config NET_DSA_VITESSE_VSC73XX
 	tristate
-	select NET_DSA_TAG_NONE
+	select NET_DSA_TAG_VSC73XX_8021Q
 	select FIXED_PHY
 	select VITESSE_PHY
 	select GPIOLIB

drivers/net/dsa/vitesse-vsc73xx-core.c

@@ -597,7 +597,7 @@ static enum dsa_tag_protocol vsc73xx_get_tag_protocol(struct dsa_switch *ds,
 	 * cannot access the tag. (See "Internal frame header" section
 	 * 3.9.1 in the manual.)
 	 */
-	return DSA_TAG_PROTO_NONE;
+	return DSA_TAG_PROTO_VSC73XX_8021Q;
 }
 
 static int vsc73xx_wait_for_vlan_table_cmd(struct vsc73xx *vsc)
@@ -687,7 +687,7 @@ vsc73xx_update_vlan_table(struct vsc73xx *vsc, int port, u16 vid, bool set)
 static int vsc73xx_setup(struct dsa_switch *ds)
 {
 	struct vsc73xx *vsc = ds->priv;
-	int i;
+	int i, ret;
 
 	dev_info(vsc->dev, "set up the switch\n");
 
@@ -768,7 +768,18 @@ static int vsc73xx_setup(struct dsa_switch *ds)
 
 	INIT_LIST_HEAD(&vsc->vlans);
 
-	return 0;
+	rtnl_lock();
+	ret = dsa_tag_8021q_register(ds, htons(ETH_P_8021Q));
+	rtnl_unlock();
+
+	return ret;
+}
+
+static void vsc73xx_teardown(struct dsa_switch *ds)
+{
+	rtnl_lock();
+	dsa_tag_8021q_unregister(ds);
+	rtnl_unlock();
 }
 
 static void vsc73xx_init_port(struct vsc73xx *vsc, int port)
@@ -1549,12 +1560,65 @@ static int vsc73xx_port_vlan_del(struct dsa_switch *ds, int port,
 		vsc73xx_bridge_vlan_remove_port(vsc73xx_vlan, port);
 
 	commit_to_hardware = !vsc73xx_tag_8021q_active(dsa_to_port(ds, port));
+
 	if (commit_to_hardware)
 		return vsc73xx_vlan_commit_settings(vsc, port);
 
 	return 0;
 }
 
+static int vsc73xx_tag_8021q_vlan_add(struct dsa_switch *ds, int port, u16 vid,
+				      u16 flags)
+{
+	bool pvid = flags & BRIDGE_VLAN_INFO_PVID;
+	struct vsc73xx_portinfo *portinfo;
+	struct vsc73xx *vsc = ds->priv;
+	bool commit_to_hardware;
+	int ret;
+
+	portinfo = &vsc->portinfo[port];
+
+	if (pvid) {
+		portinfo->pvid_tag_8021q_configured = true;
+		portinfo->pvid_tag_8021q = vid;
+	}
+
+	commit_to_hardware = vsc73xx_tag_8021q_active(dsa_to_port(ds, port));
+	if (commit_to_hardware) {
+		ret = vsc73xx_vlan_commit_settings(vsc, port);
+		if (ret)
+			return ret;
+	}
+
+	return vsc73xx_update_vlan_table(vsc, port, vid, true);
+}
+
+static int vsc73xx_tag_8021q_vlan_del(struct dsa_switch *ds, int port, u16 vid)
+{
+	struct vsc73xx_portinfo *portinfo;
+	struct vsc73xx *vsc = ds->priv;
+
+	portinfo = &vsc->portinfo[port];
+
+	if (portinfo->pvid_tag_8021q_configured &&
+	    portinfo->pvid_tag_8021q == vid) {
+		struct dsa_port *dp = dsa_to_port(ds, port);
+		bool commit_to_hardware;
+		int err;
+
+		portinfo->pvid_tag_8021q_configured = false;
+
+		commit_to_hardware = vsc73xx_tag_8021q_active(dp);
+		if (commit_to_hardware) {
+			err = vsc73xx_vlan_commit_settings(vsc, port);
+			if (err)
+				return err;
+		}
+	}
+
+	return vsc73xx_update_vlan_table(vsc, port, vid, false);
+}
+
 static void vsc73xx_refresh_fwd_map(struct dsa_switch *ds, int port, u8 state)
 {
 	struct dsa_port *other_dp, *dp = dsa_to_port(ds, port);
@@ -1644,6 +1708,7 @@ static const struct phylink_mac_ops vsc73xx_phylink_mac_ops = {
 static const struct dsa_switch_ops vsc73xx_ds_ops = {
 	.get_tag_protocol = vsc73xx_get_tag_protocol,
 	.setup = vsc73xx_setup,
+	.teardown = vsc73xx_teardown,
 	.phy_read = vsc73xx_phy_read,
 	.phy_write = vsc73xx_phy_write,
 	.get_strings = vsc73xx_get_strings,
@@ -1658,6 +1723,8 @@ static const struct dsa_switch_ops vsc73xx_ds_ops = {
 	.port_vlan_add = vsc73xx_port_vlan_add,
 	.port_vlan_del = vsc73xx_port_vlan_del,
 	.phylink_get_caps = vsc73xx_phylink_get_caps,
+	.tag_8021q_vlan_add = vsc73xx_tag_8021q_vlan_add,
+	.tag_8021q_vlan_del = vsc73xx_tag_8021q_vlan_del,
 };
 
 static int vsc73xx_gpio_get(struct gpio_chip *chip, unsigned int offset)