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Date:   Wed, 22 May 2019 15:50:50 +0200
From:   Alexandre Belloni <alexandre.belloni@...tlin.com>
To:     Claudiu Manoil <claudiu.manoil@....com>
Cc:     "David S . Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        Pavel Machek <pavel@...x.de>, UNGLinuxDriver@...rochip.com
Subject: Re: [PATCH net] ocelot: Dont allocate another multicast list, use
 __dev_mc_sync

On 21/05/2019 19:52:55+0300, Claudiu Manoil wrote:
> Doing kmalloc in atomic context is always an issue,
> more so for a list that can grow significantly.
> Turns out that the driver only uses the duplicated
> list of multicast mac addresses to keep track of
> what addresses to delete from h/w before committing
> the new list from kernel to h/w back again via set_rx_mode,
> every time this list gets updated by the kernel.
> Given that the h/w knows how to add and delete mac addresses
> based on the mac address value alone, __dev_mc_sync should be
> the much better choice of kernel API for these operations
> avoiding the considerable overhead of maintaining a duplicated
> list in the driver.
> 
> Signed-off-by: Claudiu Manoil <claudiu.manoil@....com>

Tested-by: Alexandre Belloni <alexandre.belloni@...tlin.com>
Acked-by: Alexandre Belloni <alexandre.belloni@...tlin.com>

> ---
> Maybe this should go to net, since there were objections
> for abusing kmalloc(GFP_ATOMIC).
> 
>  drivers/net/ethernet/mscc/ocelot.c | 43 ++++++------------------------
>  drivers/net/ethernet/mscc/ocelot.h |  4 ---
>  2 files changed, 8 insertions(+), 39 deletions(-)
> 
> diff --git a/drivers/net/ethernet/mscc/ocelot.c b/drivers/net/ethernet/mscc/ocelot.c
> index d715ef4fc92f..02ad11e0b0d8 100644
> --- a/drivers/net/ethernet/mscc/ocelot.c
> +++ b/drivers/net/ethernet/mscc/ocelot.c
> @@ -593,45 +593,25 @@ static int ocelot_port_xmit(struct sk_buff *skb, struct net_device *dev)
>  	return NETDEV_TX_OK;
>  }
>  
> -static void ocelot_mact_mc_reset(struct ocelot_port *port)
> +static int ocelot_mc_unsync(struct net_device *dev, const unsigned char *addr)
>  {
> -	struct ocelot *ocelot = port->ocelot;
> -	struct netdev_hw_addr *ha, *n;
> +	struct ocelot_port *port = netdev_priv(dev);
>  
> -	/* Free and forget all the MAC addresses stored in the port private mc
> -	 * list. These are mc addresses that were previously added by calling
> -	 * ocelot_mact_mc_add().
> -	 */
> -	list_for_each_entry_safe(ha, n, &port->mc, list) {
> -		ocelot_mact_forget(ocelot, ha->addr, port->pvid);
> -		list_del(&ha->list);
> -		kfree(ha);
> -	}
> +	return ocelot_mact_forget(port->ocelot, addr, port->pvid);
>  }
>  
> -static int ocelot_mact_mc_add(struct ocelot_port *port,
> -			      struct netdev_hw_addr *hw_addr)
> +static int ocelot_mc_sync(struct net_device *dev, const unsigned char *addr)
>  {
> -	struct ocelot *ocelot = port->ocelot;
> -	struct netdev_hw_addr *ha = kzalloc(sizeof(*ha), GFP_ATOMIC);
> -
> -	if (!ha)
> -		return -ENOMEM;
> -
> -	memcpy(ha, hw_addr, sizeof(*ha));
> -	list_add_tail(&ha->list, &port->mc);
> -
> -	ocelot_mact_learn(ocelot, PGID_CPU, ha->addr, port->pvid,
> -			  ENTRYTYPE_LOCKED);
> +	struct ocelot_port *port = netdev_priv(dev);
>  
> -	return 0;
> +	return ocelot_mact_learn(port->ocelot, PGID_CPU, addr, port->pvid,
> +				 ENTRYTYPE_LOCKED);
>  }
>  
>  static void ocelot_set_rx_mode(struct net_device *dev)
>  {
>  	struct ocelot_port *port = netdev_priv(dev);
>  	struct ocelot *ocelot = port->ocelot;
> -	struct netdev_hw_addr *ha;
>  	int i;
>  	u32 val;
>  
> @@ -643,13 +623,7 @@ static void ocelot_set_rx_mode(struct net_device *dev)
>  	for (i = ocelot->num_phys_ports + 1; i < PGID_CPU; i++)
>  		ocelot_write_rix(ocelot, val, ANA_PGID_PGID, i);
>  
> -	/* Handle the device multicast addresses. First remove all the
> -	 * previously installed addresses and then add the latest ones to the
> -	 * mac table.
> -	 */
> -	ocelot_mact_mc_reset(port);
> -	netdev_for_each_mc_addr(ha, dev)
> -		ocelot_mact_mc_add(port, ha);
> +	__dev_mc_sync(dev, ocelot_mc_sync, ocelot_mc_unsync);
>  }
>  
>  static int ocelot_port_get_phys_port_name(struct net_device *dev,
> @@ -1657,7 +1631,6 @@ int ocelot_probe_port(struct ocelot *ocelot, u8 port,
>  	ocelot_port->regs = regs;
>  	ocelot_port->chip_port = port;
>  	ocelot_port->phy = phy;
> -	INIT_LIST_HEAD(&ocelot_port->mc);
>  	ocelot->ports[port] = ocelot_port;
>  
>  	dev->netdev_ops = &ocelot_port_netdev_ops;
> diff --git a/drivers/net/ethernet/mscc/ocelot.h b/drivers/net/ethernet/mscc/ocelot.h
> index ba3b3380b4d0..541fe41e60b0 100644
> --- a/drivers/net/ethernet/mscc/ocelot.h
> +++ b/drivers/net/ethernet/mscc/ocelot.h
> @@ -441,10 +441,6 @@ struct ocelot_port {
>  	struct phy_device *phy;
>  	void __iomem *regs;
>  	u8 chip_port;
> -	/* Keep a track of the mc addresses added to the mac table, so that they
> -	 * can be removed when needed.
> -	 */
> -	struct list_head mc;
>  
>  	/* Ingress default VLAN (pvid) */
>  	u16 pvid;
> -- 
> 2.17.1
> 

-- 
Alexandre Belloni, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com

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