netdev - Re: [PATCH v4 net-next 4/5] net: dsa: mv88e6xxx: Link aggregation support

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Message-ID: <20201216190410.2mgrujtjfd2uvnwu@skbuf>
Date:   Wed, 16 Dec 2020 21:04:10 +0200
From:   Vladimir Oltean <olteanv@...il.com>
To:     Tobias Waldekranz <tobias@...dekranz.com>
Cc:     davem@...emloft.net, kuba@...nel.org, andrew@...n.ch,
        vivien.didelot@...il.com, f.fainelli@...il.com,
        j.vosburgh@...il.com, vfalico@...il.com, andy@...yhouse.net,
        netdev@...r.kernel.org
Subject: Re: [PATCH v4 net-next 4/5] net: dsa: mv88e6xxx: Link aggregation
 support

On Wed, Dec 16, 2020 at 05:00:55PM +0100, Tobias Waldekranz wrote:
> Support offloading of LAGs to hardware. LAGs may be attached to a
> bridge in which case VLANs, multicast groups, etc. are also offloaded
> as usual.
> 
> Signed-off-by: Tobias Waldekranz <tobias@...dekranz.com>
> ---
>  drivers/net/dsa/mv88e6xxx/chip.c    | 298 +++++++++++++++++++++++++++-
>  drivers/net/dsa/mv88e6xxx/global2.c |   8 +-
>  drivers/net/dsa/mv88e6xxx/global2.h |   5 +
>  drivers/net/dsa/mv88e6xxx/port.c    |  21 ++
>  drivers/net/dsa/mv88e6xxx/port.h    |   5 +
>  5 files changed, 329 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/net/dsa/mv88e6xxx/chip.c b/drivers/net/dsa/mv88e6xxx/chip.c
> index eafe6bedc692..bd80b3939157 100644
> --- a/drivers/net/dsa/mv88e6xxx/chip.c
> +++ b/drivers/net/dsa/mv88e6xxx/chip.c
> @@ -1189,7 +1189,8 @@ static int mv88e6xxx_set_mac_eee(struct dsa_switch *ds, int port,
>  }
>  
>  /* Mask of the local ports allowed to receive frames from a given fabric port */
> -static u16 mv88e6xxx_port_vlan(struct mv88e6xxx_chip *chip, int dev, int port)
> +static u16 mv88e6xxx_port_vlan(struct mv88e6xxx_chip *chip, int dev, int port,
> +			       struct net_device **lag)
>  {
>  	struct dsa_switch *ds = chip->ds;
>  	struct dsa_switch_tree *dst = ds->dst;
> @@ -1201,6 +1202,9 @@ static u16 mv88e6xxx_port_vlan(struct mv88e6xxx_chip *chip, int dev, int port)
>  	list_for_each_entry(dp, &dst->ports, list) {
>  		if (dp->ds->index == dev && dp->index == port) {
>  			found = true;
> +
> +			if (dp->lag_dev && lag)
> +				*lag = dp->lag_dev;
>  			break;
>  		}
>  	}

I'll let Andrew and Vivien have the decisive word, who are vastly more
familiar with mv88e6xxx than I am, but to me it looks like a bit of a
hack to put this logic here, especially since one of the two callers
(i.e. half) doesn't even care about the LAG.

> @@ -1396,14 +1402,21 @@ static int mv88e6xxx_mac_setup(struct mv88e6xxx_chip *chip)
>  
>  static int mv88e6xxx_pvt_map(struct mv88e6xxx_chip *chip, int dev, int port)
>  {
> +	struct net_device *lag = NULL;
>  	u16 pvlan = 0;
>  
>  	if (!mv88e6xxx_has_pvt(chip))
>  		return 0;
>  
>  	/* Skip the local source device, which uses in-chip port VLAN */
> -	if (dev != chip->ds->index)
> -		pvlan = mv88e6xxx_port_vlan(chip, dev, port);
> +	if (dev != chip->ds->index) {
> +		pvlan = mv88e6xxx_port_vlan(chip, dev, port, &lag);
> +
> +		if (lag) {
> +			dev = MV88E6XXX_G2_PVT_ADRR_DEV_TRUNK;
> +			port = dsa_lag_id(chip->ds->dst, lag);
> +		}
> +	}

What about the following, which should remove the need of modifying mv88e6xxx_port_vlan:

static int mv88e6xxx_pvt_map(struct mv88e6xxx_chip *chip, int dev, int port)
{
	struct dsa_switch *ds = chip->ds;
	struct net_device *lag = NULL;
	u16 pvlan = 0;

	if (!mv88e6xxx_has_pvt(chip))
		return 0;

	/* Skip the local source device, which uses in-chip port VLAN */
	if (dev != ds->index) {
		pvlan = mv88e6xxx_port_vlan(chip, dev, port);
		struct dsa_switch *other_ds;
		struct dsa_port *other_dp;

		other_ds = dsa_switch_find(ds->dst->index, dev);
		other_dp = dsa_to_port(other_ds, port);

		/* XXX needs an explanation for the reinterpreted values of
		 * dev and port
		 */
		if (other_dp->lag_dev) {
			dev = MV88E6XXX_G2_PVT_ADRR_DEV_TRUNK;
			port = dsa_lag_id(ds->dst, other_dp->lag_dev);
		}
	}

	return mv88e6xxx_g2_pvt_write(chip, dev, port, pvlan);
}

>  
>  	return mv88e6xxx_g2_pvt_write(chip, dev, port, pvlan);
>  }
> @@ -5375,6 +5388,271 @@ static int mv88e6xxx_port_egress_floods(struct dsa_switch *ds, int port,
>  	return err;
>  }
>