Re: [PATCH net-next 5/5] net: dsa: mv88e6xxx: Offload bridge broadcast flooding flag

On Tue, Mar 16, 2021 at 11:39, Vladimir Oltean [off-list ref] wrote:

On Mon, Mar 15, 2021 at 10:14:00PM +0100, Tobias Waldekranz wrote:

quoted

These switches have two modes of classifying broadcast:

1. Broadcast is multicast.
2. Broadcast is its own unique thing that is always flooded
   everywhere.

This driver uses the first option, making sure to load the broadcast
address into all active databases. Because of this, we can support
per-port broadcast flooding by (1) making sure to only set the subset
of ports that have it enabled whenever joining a new bridge or VLAN,
and (2) by updating all active databases whenever the setting is
changed on a port.

Signed-off-by: Tobias Waldekranz <tobias@waldekranz.com>
---
 drivers/net/dsa/mv88e6xxx/chip.c | 68 +++++++++++++++++++++++++++++++-
 1 file changed, 67 insertions(+), 1 deletion(-)

diff --git a/drivers/net/dsa/mv88e6xxx/chip.c b/drivers/net/dsa/mv88e6xxx/chip.c
index 48e65f22641e..e6987c501fb7 100644
--- a/drivers/net/dsa/mv88e6xxx/chip.c
+++ b/drivers/net/dsa/mv88e6xxx/chip.c

@@ -1950,6 +1950,18 @@ static int mv88e6xxx_broadcast_setup(struct mv88e6xxx_chip *chip, u16 vid)
 	int err;
 
 	for (port = 0; port < mv88e6xxx_num_ports(chip); port++) {
+		struct dsa_port *dp = dsa_to_port(chip->ds, port);
+
+		if (dsa_is_unused_port(chip->ds, port))
+			continue;
+
+		if (dsa_is_user_port(chip->ds, port) && dp->bridge_dev &&
+		    !br_port_flag_is_set(dp->slave, BR_BCAST_FLOOD))

What if dp->slave is not the bridge port, but a LAG? br_port_flag_is_set
will return false.

Good point. I see two ways forward:

- My first idea was to cache a vector per switch that would act as the
  template when creating a new entry. This avoids having the driver
  layer knowing about stacked netdevs etc. But I think that Andrew is
  generally opposed to caching?

- Add a new helper at the dsa layer that takes a dp and returns the
  netdev that is attached to the bridge, if any:

  struct net_device *dsa_port_to_bridge_port(struct dsa_port *dp)

Any preference or other ideas?

Speaking of, shouldn't mv88e6xxx_port_vlan_join also be called from
mv88e6xxx_port_bridge_join somehow, or are we waiting for the bridge
facility to replay VLANs added to the LAG when we emit the offload
notification for it?

I do not think so. VLANs are always added via the .port_vlan_add
callback, no?

Potentially the bridge is of the non-filtering variety, so it could be
that no VLANs are ever added.

Or do you mean (the most confusingly named feature Marvell LinkStreet
devices) port-based VLANs? Those are setup on a bridge join via
mv88e6xxx_port_vlan_map and mv88e6xxx_pvt_map.

quoted

+			/* Skip bridged user ports where broadcast
+			 * flooding is disabled.
+			 */
+			continue;
+
 		err = mv88e6xxx_port_add_broadcast(chip, port, vid);
 		if (err)
 			return err;

@@ -1958,6 +1970,51 @@ static int mv88e6xxx_broadcast_setup(struct mv88e6xxx_chip *chip, u16 vid)
 	return 0;
 }
 
+struct mv88e6xxx_port_broadcast_sync_ctx {
+	int port;
+	bool flood;
+};
+
+static int
+mv88e6xxx_port_broadcast_sync_vlan(struct mv88e6xxx_chip *chip,
+				   const struct mv88e6xxx_vtu_entry *vlan,
+				   void *_ctx)
+{
+	const char broadcast[6] = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };

MAC addresses are usually defined as unsigned char[ETH_ALEN]. You can
also use eth_broadcast_addr(broadcast) for initialization.

I was going for uniformity with mv88e6xxx_port_add_broadcast. But I will
add a clean-up commit that fixes the existing code first, and then adds
this definition in the proper way.

quoted

+	struct mv88e6xxx_port_broadcast_sync_ctx *ctx = _ctx;
+	u8 state;
+
+	if (ctx->flood)
+		state = MV88E6XXX_G1_ATU_DATA_STATE_MC_STATIC;
+	else
+		state = MV88E6XXX_G1_ATU_DATA_STATE_MC_UNUSED;
+
+	return mv88e6xxx_port_db_load_purge(chip, ctx->port, broadcast,
+					    vlan->vid, state);
+}
+
+static int mv88e6xxx_port_broadcast_sync(struct mv88e6xxx_chip *chip, int port,
+					 bool flood)
+{
+	struct mv88e6xxx_port_broadcast_sync_ctx ctx = {
+		.port = port,
+		.flood = flood,
+	};
+	struct mv88e6xxx_vtu_entry vid0 = {
+		.vid = 0,
+	};
+	int err;
+
+	/* Update the port's private database... */
+	err = mv88e6xxx_port_broadcast_sync_vlan(chip, &vid0, &ctx);
+	if (err)
+		return err;
+
+	/* ...and the database for all VLANs. */
+	return mv88e6xxx_vtu_walk(chip, mv88e6xxx_port_broadcast_sync_vlan,
+				  &ctx);
+}
+
 static int mv88e6xxx_port_vlan_join(struct mv88e6xxx_chip *chip, int port,
 				    u16 vid, u8 member, bool warn)
 {

@@ -5431,7 +5488,8 @@ static int mv88e6xxx_port_pre_bridge_flags(struct dsa_switch *ds, int port,
 	struct mv88e6xxx_chip *chip = ds->priv;
 	const struct mv88e6xxx_ops *ops;
 
-	if (flags.mask & ~(BR_LEARNING | BR_FLOOD | BR_MCAST_FLOOD))
+	if (flags.mask & ~(BR_LEARNING | BR_FLOOD | BR_MCAST_FLOOD |
+			   BR_BCAST_FLOOD))
 		return -EINVAL;
 
 	ops = chip->info->ops;

@@ -5480,6 +5538,14 @@ static int mv88e6xxx_port_bridge_flags(struct dsa_switch *ds, int port,
 			goto out;
 	}
 
+	if (flags.mask & BR_BCAST_FLOOD) {
+		bool broadcast = !!(flags.val & BR_BCAST_FLOOD);
+
+		err = mv88e6xxx_port_broadcast_sync(chip, port, broadcast);
+		if (err)
+			goto out;
+	}
+
 out:
 	mv88e6xxx_reg_unlock(chip);
 

-- 
2.25.1