target/linux/generic/backport-5.15/765-v5.17-03-net-next-net-dsa-stop-updating-master-MTU-from-master.c.patch

   1 From a1ff94c2973c43bc1e2677ac63ebb15b1d1ff846 Mon Sep 17 00:00:00 2001
   2 From: Vladimir Oltean <vladimir.oltean@nxp.com>
   3 Date: Thu, 6 Jan 2022 01:11:14 +0200
   4 Subject: [PATCH 3/6] net: dsa: stop updating master MTU from master.c
   5
   6 At present there are two paths for changing the MTU of the DSA master.
   7
   8 The first is:
   9
  10 dsa_tree_setup
  11 -> dsa_tree_setup_ports
  12    -> dsa_port_setup
  13       -> dsa_slave_create
  14          -> dsa_slave_change_mtu
  15             -> dev_set_mtu(master)
  16
  17 The second is:
  18
  19 dsa_tree_setup
  20 -> dsa_tree_setup_master
  21    -> dsa_master_setup
  22       -> dev_set_mtu(dev)
  23
  24 So the dev_set_mtu() call from dsa_master_setup() has been effectively
  25 superseded by the dsa_slave_change_mtu(slave_dev, ETH_DATA_LEN) that is
  26 done from dsa_slave_create() for each user port. The later function also
  27 updates the master MTU according to the largest user port MTU from the
  28 tree. Therefore, updating the master MTU through a separate code path
  29 isn't needed.
  30
  31 Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
  32 Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
  33 Signed-off-by: David S. Miller <davem@davemloft.net>
  34 ---
  35  net/dsa/master.c | 25 +------------------------
  36  1 file changed, 1 insertion(+), 24 deletions(-)
  37
  38 --- a/net/dsa/master.c
  39 +++ b/net/dsa/master.c
  40 @@ -329,28 +329,13 @@ static const struct attribute_group dsa_
  41         .attrs  = dsa_slave_attrs,
  42  };
  43
  44 -static void dsa_master_reset_mtu(struct net_device *dev)
  45 -{
  46 -       int err;
  47 -
  48 -       rtnl_lock();
  49 -       err = dev_set_mtu(dev, ETH_DATA_LEN);
  50 -       if (err)
  51 -               netdev_dbg(dev,
  52 -                          "Unable to reset MTU to exclude DSA overheads\n");
  53 -       rtnl_unlock();
  54 -}
  55 -
  56  static struct lock_class_key dsa_master_addr_list_lock_key;
  57
  58  int dsa_master_setup(struct net_device *dev, struct dsa_port *cpu_dp)
  59  {
  60 -       const struct dsa_device_ops *tag_ops = cpu_dp->tag_ops;
  61         struct dsa_switch *ds = cpu_dp->ds;
  62         struct device_link *consumer_link;
  63 -       int mtu, ret;
  64 -
  65 -       mtu = ETH_DATA_LEN + dsa_tag_protocol_overhead(tag_ops);
  66 +       int ret;
  67
  68         /* The DSA master must use SET_NETDEV_DEV for this to work. */
  69         consumer_link = device_link_add(ds->dev, dev->dev.parent,
  70 @@ -360,13 +345,6 @@ int dsa_master_setup(struct net_device *
  71                            "Failed to create a device link to DSA switch %s\n",
  72                            dev_name(ds->dev));
  73
  74 -       rtnl_lock();
  75 -       ret = dev_set_mtu(dev, mtu);
  76 -       rtnl_unlock();
  77 -       if (ret)
  78 -               netdev_warn(dev, "error %d setting MTU to %d to include DSA overhead\n",
  79 -                           ret, mtu);
  80 -
  81         /* If we use a tagging format that doesn't have an ethertype
  82          * field, make sure that all packets from this point on get
  83          * sent to the tag format's receive function.
  84 @@ -404,7 +382,6 @@ void dsa_master_teardown(struct net_devi
  85         sysfs_remove_group(&dev->dev.kobj, &dsa_group);
  86         dsa_netdev_ops_set(dev, NULL);
  87         dsa_master_ethtool_teardown(dev);
  88 -       dsa_master_reset_mtu(dev);
  89         dsa_master_set_promiscuity(dev, -1);
  90
  91         dev->dsa_ptr = NULL;