[net-next RFC PATCH v4 02/15] net: dsa: stop updating master MTU from master.c

Ansuel Smith
2021-12-11T19:58:25Z

From: Vladimir Oltean <vladimir.oltean@nxp.com>

The dev_set_mtu() call from dsa_master_setup() has been effectively
superseded by the dsa_slave_change_mtu(slave_dev, ETH_DATA_LEN) that is
done from dsa_slave_create() for each user port. This function also
updates the master MTU according to the largest user port MTU from the
tree. Therefore, updating the master MTU through a separate code path
isn't needed.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
net/dsa/master.c | 25 +------------------------
1 file changed, 1 insertion(+), 24 deletions(-)

diff --git a/net/dsa/master.c b/net/dsa/master.c
index e8e19857621b..f4efb244f91d 100644
--- a/net/dsa/master.c
+++ b/net/dsa/master.c
@@ -330,28 +330,13 @@ static const struct attribute_group dsa_group = {
.attrs = dsa_slave_attrs,
};

-static void dsa_master_reset_mtu(struct net_device *dev)
-{
- int err;
-
- rtnl_lock();
- err = dev_set_mtu(dev, ETH_DATA_LEN);
- if (err)
- netdev_dbg(dev,
- "Unable to reset MTU to exclude DSA overheads\n");
- rtnl_unlock();
-}
-
static struct lock_class_key dsa_master_addr_list_lock_key;

int dsa_master_setup(struct net_device *dev, struct dsa_port *cpu_dp)
{
- const struct dsa_device_ops *tag_ops = cpu_dp->tag_ops;
struct dsa_switch *ds = cpu_dp->ds;
struct device_link *consumer_link;
- int mtu, ret;
-
- mtu = ETH_DATA_LEN + dsa_tag_protocol_overhead(tag_ops);
+ int ret;

/* The DSA master must use SET_NETDEV_DEV for this to work. */
consumer_link = device_link_add(ds->dev, dev->dev.parent,
@@ -361,13 +346,6 @@ int dsa_master_setup(struct net_device *dev, struct dsa_port *cpu_dp)
"Failed to create a device link to DSA switch %s\n",
dev_name(ds->dev));

- rtnl_lock();
- ret = dev_set_mtu(dev, mtu);
- rtnl_unlock();
- if (ret)
- netdev_warn(dev, "error %d setting MTU to %d to include DSA overhead\n",
- ret, mtu);
-
/* If we use a tagging format that doesn't have an ethertype
* field, make sure that all packets from this point on get
* sent to the tag format's receive function.
@@ -405,7 +383,6 @@ void dsa_master_teardown(struct net_device *dev)
sysfs_remove_group(&dev->dev.kobj, &dsa_group);
dsa_netdev_ops_set(dev, NULL);
dsa_master_ethtool_teardown(dev);
- dsa_master_reset_mtu(dev);
dsa_master_set_promiscuity(dev, -1);

dev->dsa_ptr = NULL;
--
2.32.0