5 files changed, 171 insertions, 16 deletions

diff --git a/net/dsa/dsa_priv.h b/net/dsa/dsa_priv.h
index 760e6ea3178a..da3be60beefe 100644
--- a/net/dsa/dsa_priv.h
+++ b/net/dsa/dsa_priv.h
@@ -22,6 +22,7 @@ enum {
 	DSA_NOTIFIER_MDB_DEL,
 	DSA_NOTIFIER_VLAN_ADD,
 	DSA_NOTIFIER_VLAN_DEL,
+	DSA_NOTIFIER_MTU,
 };
 
 /* DSA_NOTIFIER_AGEING_TIME */
@@ -61,6 +62,14 @@ struct dsa_notifier_vlan_info {
 	int port;
 };
 
+/* DSA_NOTIFIER_MTU */
+struct dsa_notifier_mtu_info {
+	bool propagate_upstream;
+	int sw_index;
+	int port;
+	int mtu;
+};
+
 struct dsa_slave_priv {
 	/* Copy of CPU port xmit for faster access in slave transmit hot path */
 	struct sk_buff *	(*xmit)(struct sk_buff *skb,
@@ -127,6 +136,8 @@ int dsa_port_vlan_filtering(struct dsa_port *dp, bool vlan_filtering,
 			    struct switchdev_trans *trans);
 int dsa_port_ageing_time(struct dsa_port *dp, clock_t ageing_clock,
 			 struct switchdev_trans *trans);
+int dsa_port_mtu_change(struct dsa_port *dp, int new_mtu,
+			bool propagate_upstream);
 int dsa_port_fdb_add(struct dsa_port *dp, const unsigned char *addr,
 		     u16 vid);
 int dsa_port_fdb_del(struct dsa_port *dp, const unsigned char *addr,
diff --git a/net/dsa/master.c b/net/dsa/master.c
index bd44bde272f4..b5c535af63a3 100644
--- a/net/dsa/master.c
+++ b/net/dsa/master.c
@@ -314,20 +314,6 @@ static const struct attribute_group dsa_group = {
 	.attrs	= dsa_slave_attrs,
 };
 
-static void dsa_master_set_mtu(struct net_device *dev, struct dsa_port *cpu_dp)
-{
-	unsigned int mtu = ETH_DATA_LEN + cpu_dp->tag_ops->overhead;
-	int err;
-
-	rtnl_lock();
-	if (mtu <= dev->max_mtu) {
-		err = dev_set_mtu(dev, mtu);
-		if (err)
-			netdev_dbg(dev, "Unable to set MTU to include for DSA overheads\n");
-	}
-	rtnl_unlock();
-}
-
 static void dsa_master_reset_mtu(struct net_device *dev)
 {
 	int err;
@@ -344,7 +330,12 @@ int dsa_master_setup(struct net_device *dev, struct dsa_port *cpu_dp)
 {
 	int ret;
 
-	dsa_master_set_mtu(dev,  cpu_dp);
+	rtnl_lock();
+	ret = dev_set_mtu(dev, ETH_DATA_LEN + cpu_dp->tag_ops->overhead);
+	rtnl_unlock();
+	if (ret)
+		netdev_warn(dev, "error %d setting MTU to include DSA overhead\n",
+			    ret);
 
 	/* If we use a tagging format that doesn't have an ethertype
 	 * field, make sure that all packets from this point on get
diff --git a/net/dsa/port.c b/net/dsa/port.c
index a18e65a474a5..231b2d494f1c 100644
--- a/net/dsa/port.c
+++ b/net/dsa/port.c
@@ -297,6 +297,19 @@ int dsa_port_mrouter(struct dsa_port *dp, bool mrouter,
 	return ds->ops->port_egress_floods(ds, port, true, mrouter);
 }
 
+int dsa_port_mtu_change(struct dsa_port *dp, int new_mtu,
+			bool propagate_upstream)
+{
+	struct dsa_notifier_mtu_info info = {
+		.sw_index = dp->ds->index,
+		.propagate_upstream = propagate_upstream,
+		.port = dp->index,
+		.mtu = new_mtu,
+	};
+
+	return dsa_port_notify(dp, DSA_NOTIFIER_MTU, &info);
+}
+
 int dsa_port_fdb_add(struct dsa_port *dp, const unsigned char *addr,
 		     u16 vid)
 {
diff --git a/net/dsa/slave.c b/net/dsa/slave.c
index 5f782fa3029f..1a99bbab0722 100644
--- a/net/dsa/slave.c
+++ b/net/dsa/slave.c
@@ -1218,6 +1218,96 @@ static int dsa_slave_vlan_rx_kill_vid(struct net_device *dev, __be16 proto,
 	return dsa_port_vid_del(dp, vid);
 }
 
+static int dsa_slave_change_mtu(struct net_device *dev, int new_mtu)
+{
+	struct net_device *master = dsa_slave_to_master(dev);
+	struct dsa_port *dp = dsa_slave_to_port(dev);
+	struct dsa_slave_priv *p = netdev_priv(dev);
+	struct dsa_switch *ds = p->dp->ds;
+	struct dsa_port *cpu_dp;
+	int port = p->dp->index;
+	int largest_mtu = 0;
+	int new_master_mtu;
+	int old_master_mtu;
+	int mtu_limit;
+	int cpu_mtu;
+	int err, i;
+
+	if (!ds->ops->port_change_mtu)
+		return -EOPNOTSUPP;
+
+	for (i = 0; i < ds->num_ports; i++) {
+		int slave_mtu;
+
+		if (!dsa_is_user_port(ds, i))
+			continue;
+
+		/* During probe, this function will be called for each slave
+		 * device, while not all of them have been allocated. That's
+		 * ok, it doesn't change what the maximum is, so ignore it.
+		 */
+		if (!dsa_to_port(ds, i)->slave)
+			continue;
+
+		/* Pretend that we already applied the setting, which we
+		 * actually haven't (still haven't done all integrity checks)
+		 */
+		if (i == port)
+			slave_mtu = new_mtu;
+		else
+			slave_mtu = dsa_to_port(ds, i)->slave->mtu;
+
+		if (largest_mtu < slave_mtu)
+			largest_mtu = slave_mtu;
+	}
+
+	cpu_dp = dsa_to_port(ds, port)->cpu_dp;
+
+	mtu_limit = min_t(int, master->max_mtu, dev->max_mtu);
+	old_master_mtu = master->mtu;
+	new_master_mtu = largest_mtu + cpu_dp->tag_ops->overhead;
+	if (new_master_mtu > mtu_limit)
+		return -ERANGE;
+
+	/* If the master MTU isn't over limit, there's no need to check the CPU
+	 * MTU, since that surely isn't either.
+	 */
+	cpu_mtu = largest_mtu;
+
+	/* Start applying stuff */
+	if (new_master_mtu != old_master_mtu) {
+		err = dev_set_mtu(master, new_master_mtu);
+		if (err < 0)
+			goto out_master_failed;
+
+		/* We only need to propagate the MTU of the CPU port to
+		 * upstream switches.
+		 */
+		err = dsa_port_mtu_change(cpu_dp, cpu_mtu, true);
+		if (err)
+			goto out_cpu_failed;
+	}
+
+	err = dsa_port_mtu_change(dp, new_mtu, false);
+	if (err)
+		goto out_port_failed;
+
+	dev->mtu = new_mtu;
+
+	return 0;
+
+out_port_failed:
+	if (new_master_mtu != old_master_mtu)
+		dsa_port_mtu_change(cpu_dp, old_master_mtu -
+				    cpu_dp->tag_ops->overhead,
+				    true);
+out_cpu_failed:
+	if (new_master_mtu != old_master_mtu)
+		dev_set_mtu(master, old_master_mtu);
+out_master_failed:
+	return err;
+}
+
 static const struct ethtool_ops dsa_slave_ethtool_ops = {
 	.get_drvinfo		= dsa_slave_get_drvinfo,
 	.get_regs_len		= dsa_slave_get_regs_len,
@@ -1295,6 +1385,7 @@ static const struct net_device_ops dsa_slave_netdev_ops = {
 	.ndo_vlan_rx_add_vid	= dsa_slave_vlan_rx_add_vid,
 	.ndo_vlan_rx_kill_vid	= dsa_slave_vlan_rx_kill_vid,
 	.ndo_get_devlink_port	= dsa_slave_get_devlink_port,
+	.ndo_change_mtu		= dsa_slave_change_mtu,
 };
 
 static struct device_type dsa_type = {
@@ -1465,7 +1556,10 @@ int dsa_slave_create(struct dsa_port *port)
 	slave_dev->priv_flags |= IFF_NO_QUEUE;
 	slave_dev->netdev_ops = &dsa_slave_netdev_ops;
 	slave_dev->min_mtu = 0;
-	slave_dev->max_mtu = ETH_MAX_MTU;
+	if (ds->ops->port_max_mtu)
+		slave_dev->max_mtu = ds->ops->port_max_mtu(ds, port->index);
+	else
+		slave_dev->max_mtu = ETH_MAX_MTU;
 	SET_NETDEV_DEVTYPE(slave_dev, &dsa_type);
 
 	SET_NETDEV_DEV(slave_dev, port->ds->dev);
@@ -1483,6 +1577,15 @@ int dsa_slave_create(struct dsa_port *port)
 	p->xmit = cpu_dp->tag_ops->xmit;
 	port->slave = slave_dev;
 
+	rtnl_lock();
+	ret = dsa_slave_change_mtu(slave_dev, ETH_DATA_LEN);
+	rtnl_unlock();
+	if (ret && ret != -EOPNOTSUPP) {
+		dev_err(ds->dev, "error %d setting MTU on port %d\n",
+			ret, port->index);
+		goto out_free;
+	}
+
 	netif_carrier_off(slave_dev);
 
 	ret = dsa_slave_phy_setup(slave_dev);
diff --git a/net/dsa/switch.c b/net/dsa/switch.c
index df4abe897ed6..f3c32ff552b3 100644
--- a/net/dsa/switch.c
+++ b/net/dsa/switch.c
@@ -52,6 +52,40 @@ static int dsa_switch_ageing_time(struct dsa_switch *ds,
 	return 0;
 }
 
+static bool dsa_switch_mtu_match(struct dsa_switch *ds, int port,
+				 struct dsa_notifier_mtu_info *info)
+{
+	if (ds->index == info->sw_index)
+		return (port == info->port) || dsa_is_dsa_port(ds, port);
+
+	if (!info->propagate_upstream)
+		return false;
+
+	if (dsa_is_dsa_port(ds, port) || dsa_is_cpu_port(ds, port))
+		return true;
+
+	return false;
+}
+
+static int dsa_switch_mtu(struct dsa_switch *ds,
+			  struct dsa_notifier_mtu_info *info)
+{
+	int port, ret;
+
+	if (!ds->ops->port_change_mtu)
+		return -EOPNOTSUPP;
+
+	for (port = 0; port < ds->num_ports; port++) {
+		if (dsa_switch_mtu_match(ds, port, info)) {
+			ret = ds->ops->port_change_mtu(ds, port, info->mtu);
+			if (ret)
+				return ret;
+		}
+	}
+
+	return 0;
+}
+
 static int dsa_switch_bridge_join(struct dsa_switch *ds,
 				  struct dsa_notifier_bridge_info *info)
 {
@@ -328,6 +362,9 @@ static int dsa_switch_event(struct notifier_block *nb,
 	case DSA_NOTIFIER_VLAN_DEL:
 		err = dsa_switch_vlan_del(ds, info);
 		break;
+	case DSA_NOTIFIER_MTU:
+		err = dsa_switch_mtu(ds, info);
+		break;
 	default:
 		err = -EOPNOTSUPP;
 		break;