Re: [PATCH net-next v2 5/6] net: dsa: mv88e6xxx: MQPRIO support

On Tue, Jun 02, 2026 at 10:43:50AM +1000, Luke Howard wrote:
> +static int mv88e6xxx_setup_tc_mqprio(struct dsa_switch *ds, int port,
> +				     struct tc_mqprio_qopt_offload *mqprio)
> +{
> +	struct netlink_ext_ack *extack = mqprio->extack;
> +	u8 ieee_pri_map[IEEE_8021Q_MAX_PRIORITIES];
> +	struct mv88e6xxx_chip *chip = ds->priv;
> +	struct mv88e6xxx_tc_policy *pol;
> +	enum mv88e6xxx_tc_mode tc_mode;
> +	struct net_device *user;
> +	bool can_update_pol;
> +	bool per_port_pol;
> +	int num_tc, err;
> +
> +	if (!dsa_is_user_port(ds, port))
> +		return -EINVAL;
> +
> +	num_tc = mv88e6xxx_validate_tc_mqprio(chip, mqprio, &tc_mode, ieee_pri_map);
> +	if (num_tc < 0)
> +		return num_tc;
> +
> +	user = dsa_to_port(ds, port)->user;
> +
> +	per_port_pol = (tc_mode == MV88E6XXX_TC_MODE_QPRI &&
> +			chip->info->ops->port_ieee_pri_map);
> +
> +	mv88e6xxx_reg_lock(chip);
> +
> +	pol = &chip->tc_policy;
> +
> +	if (num_tc && pol->tc_mode && pol->tc_mode != tc_mode) {
> +		NL_SET_ERR_MSG_MOD(extack, "all switch ports must use the same MQPRIO mode");
> +		err = -EOPNOTSUPP;
> +		goto err_unlock;
> +	}
> +
> +	can_update_pol = per_port_pol ||
> +			 !pol->tc_port_mask || pol->tc_port_mask == BIT(port);
> +	if (!can_update_pol && num_tc &&
> +	    !mv88e6xxx_tc_mode_map_equal(chip, tc_mode, ieee_pri_map)) {
> +		NL_SET_ERR_MSG_MOD(extack, "only a single priority mapping supported per switch");
> +		err = -EOPNOTSUPP;
> +		goto err_unlock;
> +	}
> +
> +	err = mv88e6xxx_mqprio_netdev_set_tc(user, &mqprio->qopt, num_tc);
> +	if (err)
> +		goto err_reset_tc;
> +
> +	if (can_update_pol) {
> +		const u8 *map = num_tc ? ieee_pri_map : NULL;
> +
> +		if (per_port_pol)
> +			err = mv88e6xxx_set_port_ieee_pri_map(chip, port, map);
> +		else
> +			err = mv88e6xxx_set_ieee_pri_map(chip, map);

In case of per port priority mapping, i don't know if this is working as
expected, as the IEEE priority mapping is done at ingress.
Eg. i think if MQPRIO channel mode is used to configure a pcp to queue mapping
on port 1 and a different mapping on port 2. Traffic received on port 1 that
gets forwarded to port 2 and egresses port 2 will end up in the queue
configured by the mapping on port 1. As mqprio is an egress qdisc, i don't
think that's expected.

I have a patch that hasn't been submitted to the mailing list yet which
implements support for the dcb app pcp-prio command. This is also done by
configuring the IEEE priority mapping table.

Cedric