On Tue, Mar 23, 2021 at 12:38:10AM +0100, Andrew Lunn wrote:
> > +static void owl_emac_set_multicast(struct net_device *netdev, int count)
> > +{
> > + struct owl_emac_priv *priv = netdev_priv(netdev);
> > + struct netdev_hw_addr *ha;
> > + int index = 0;
> > +
> > + if (count <= 0) {
> > + priv->mcaddr_list.count = 0;
> > + return;
> > + }
> > +
> > + netdev_for_each_mc_addr(ha, netdev) {
> > + if (!is_multicast_ether_addr(ha->addr))
> > + continue;
>
> Is this possible?
I remember I've seen this in one of the drivers I have studied, but
I'm not really sure it is actually necessary. I added it to be on the
safe side..
> > +
> > + WARN_ON(index >= OWL_EMAC_MAX_MULTICAST_ADDRS);
> > + ether_addr_copy(priv->mcaddr_list.addrs[index++], ha->addr);
> > + }
> > +
> > + priv->mcaddr_list.count = index;
> > +
> > + owl_emac_setup_frame_xmit(priv);
> > +}
> > +
> > +static void owl_emac_ndo_set_rx_mode(struct net_device *netdev)
> > +{
> > + struct owl_emac_priv *priv = netdev_priv(netdev);
> > + u32 status, val = 0;
> > + int mcast_count = 0;
> > +
> > + if (netdev->flags & IFF_PROMISC) {
> > + val = OWL_EMAC_BIT_MAC_CSR6_PR;
> > + } else if (netdev->flags & IFF_ALLMULTI) {
> > + val = OWL_EMAC_BIT_MAC_CSR6_PM;
> > + } else if (netdev->flags & IFF_MULTICAST) {
> > + mcast_count = netdev_mc_count(netdev);
> > +
> > + if (mcast_count > OWL_EMAC_MAX_MULTICAST_ADDRS) {
> > + val = OWL_EMAC_BIT_MAC_CSR6_PM;
> > + mcast_count = 0;
> > + }
> > + }
> > +
> > + spin_lock_bh(&priv->lock);
> > +
> > + /* Temporarily stop DMA TX & RX. */
> > + status = owl_emac_dma_cmd_stop(priv);
> > +
> > + /* Update operation modes. */
> > + owl_emac_reg_update(priv, OWL_EMAC_REG_MAC_CSR6,
> > + OWL_EMAC_BIT_MAC_CSR6_PR | OWL_EMAC_BIT_MAC_CSR6_PM,
> > + val);
> > +
> > + /* Restore DMA TX & RX status. */
> > + owl_emac_dma_cmd_set(priv, status);
> > +
> > + spin_unlock_bh(&priv->lock);
> > +
> > + /* Set/reset multicast addr list. */
> > + owl_emac_set_multicast(netdev, mcast_count);
> > +}
>
> I think this can be simplified. At least, you had me going around in
> circles a while trying to see if WARN_ON() could be triggered from
> user space.
>
> If you have more than OWL_EMAC_MAX_MULTICAST_ADDRS MC addresses, you
> go into promisc mode. Can you then skip calling
> owl_emac_set_multicast(), which appears not to do too much useful when
> passed 0?
The main purpose of always calling owl_emac_set_multicast() is to ensure
the size of the mcaddr_list is correctly updated (either set or reset).
This prevents owl_emac_setup_frame_xmit() using obsolete data, when
invoked from different contexts (i.e. MAC address changed).
A conditional call involves splitting the mcaddr_list management logic
(i.e. moving the 'reset' operation from the callee to the caller), which
IMO would make the usage of a separate function less justified.
Thanks,
Cristi
>
> Andrew
