[PATCH net-next 6/6] net: dsa: tag_8021q: Restore bridge pvid when enabling vlan_filtering

[Vladimir Oltean <olteanv@gmail.com>]

The bridge core assumes that enabling/disabling vlan_filtering will
translate into the simple toggling of a flag for switchdev drivers.

That is clearly not the case for sja1105, which alters the VLAN table
and the pvids in order to obtain port separation in standalone mode.

So, since the bridge will not call any vlan operation through switchdev
after enabling vlan_filtering, we need to ensure we're in a functional
state ourselves.

Hence read the pvid that the bridge is aware of, and program that into
our ports.

Signed-off-by: Vladimir Oltean <olteanv@gmail.com>
---
 net/dsa/tag_8021q.c | 32 +++++++++++++++++++++++++++++++-
 1 file changed, 31 insertions(+), 1 deletion(-)

diff --git a/net/dsa/tag_8021q.c b/net/dsa/tag_8021q.c
index 67a1bc635a7b..6423beb1efcd 100644
--- a/net/dsa/tag_8021q.c
+++ b/net/dsa/tag_8021q.c
@@ -93,6 +93,33 @@ int dsa_8021q_rx_source_port(u16 vid)
 }
 EXPORT_SYMBOL_GPL(dsa_8021q_rx_source_port);
 
+static int dsa_port_restore_pvid(struct dsa_switch *ds, int port)
+{
+	struct bridge_vlan_info vinfo;
+	struct net_device *slave;
+	u16 pvid;
+	int err;
+
+	if (!dsa_is_user_port(ds, port))
+		return 0;
+
+	slave = ds->ports[port].slave;
+
+	err = br_vlan_get_pvid(slave, &pvid);
+	if (err < 0) {
+		dev_err(ds->dev, "Couldn't determine bridge PVID\n");
+		return err;
+	}
+
+	err = br_vlan_get_info(slave, pvid, &vinfo);
+	if (err < 0) {
+		dev_err(ds->dev, "Couldn't determine PVID attributes\n");
+		return err;
+	}
+
+	return dsa_port_vid_add(&ds->ports[port], pvid, vinfo.flags);
+}
+
 /* RX VLAN tagging (left) and TX VLAN tagging (right) setup shown for a single
  * front-panel switch port (here swp0).
  *
@@ -223,7 +250,10 @@ int dsa_port_setup_8021q_tagging(struct dsa_switch *ds, int port, bool enabled)
 		return err;
 	}
 
-	return 0;
+	if (!enabled)
+		err = dsa_port_restore_pvid(ds, port);
+
+	return err;
 }
 EXPORT_SYMBOL_GPL(dsa_port_setup_8021q_tagging);
 
-- 
2.17.1