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Miller" , Jakub Kicinski , Rob Herring , Andreas =?iso-8859-1?Q?F=E4rber?= , Manivannan Sadhasivam , Philipp Zabel , netdev@vger.kernel.org, devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-actions@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 2/3] net: ethernet: actions: Add Actions Semi Owl Ethernet MAC driver Message-ID: <20210323083409.GA1559969@BV030612LT> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: devicetree@vger.kernel.org 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