Subject: Re: [PATCH v2 net-next 10/10] net: dsa: mv88e6xxx: MST Offloading

From: Tobias Waldekranz <[email-masked]>
Date: Thu, 10 Mar 2022 16:14:31 +0100

On Fri, Mar 04, 2022 at 00:26, Vladimir Oltean <[email-masked]> wrote:
> On Tue, Mar 01, 2022 at 11:03:21AM +0100, Tobias Waldekranz wrote:
>> Allocate a SID in the STU for each MSTID in use by a bridge and handle
>> the mapping of MSTIDs to VLANs using the SID field of each VTU entry.
>> 
>> Signed-off-by: Tobias Waldekranz <[email-masked]>
>> ---
>>  drivers/net/dsa/mv88e6xxx/chip.c | 178 +++++++++++++++++++++++++++++++
>>  drivers/net/dsa/mv88e6xxx/chip.h |  13 +++
>>  2 files changed, 191 insertions(+)
>> 
>> diff --git a/drivers/net/dsa/mv88e6xxx/chip.c b/drivers/net/dsa/mv88e6xxx/chip.c
>> index c14a62aa6a6c..4fb4ec1dff79 100644
>> --- a/drivers/net/dsa/mv88e6xxx/chip.c
>> +++ b/drivers/net/dsa/mv88e6xxx/chip.c
>> @@ -1818,6 +1818,137 @@ static int mv88e6xxx_stu_setup(struct mv88e6xxx_chip *chip)
>>  	return mv88e6xxx_stu_loadpurge(chip, &stu);
>>  }
>>  
>> +static int mv88e6xxx_sid_new(struct mv88e6xxx_chip *chip, u8 *sid)
>> +{
>> +	DECLARE_BITMAP(busy, MV88E6XXX_N_SID) = { 0 };
>> +	struct mv88e6xxx_mst *mst;
>> +
>> +	set_bit(0, busy);
>> +
>> +	list_for_each_entry(mst, &chip->msts, node) {
>> +		set_bit(mst->stu.sid, busy);
>> +	}
>> +
>> +	*sid = find_first_zero_bit(busy, MV88E6XXX_N_SID);
>> +
>> +	return (*sid >= mv88e6xxx_max_sid(chip)) ? -ENOSPC : 0;
>> +}
>> +
>> +static int mv88e6xxx_sid_put(struct mv88e6xxx_chip *chip, u8 sid)
>> +{
>> +	struct mv88e6xxx_mst *mst, *tmp;
>> +	int err = 0;
>> +
>> +	list_for_each_entry_safe(mst, tmp, &chip->msts, node) {
>> +		if (mst->stu.sid == sid) {
>> +			if (refcount_dec_and_test(&mst->refcnt)) {
>> +				mst->stu.valid = false;
>> +				err = mv88e6xxx_stu_loadpurge(chip, &mst->stu);
>
> It is interesting what to do if this fails. Possibly not this, because
> the entry remains in hardware but not in software.

True, I will let the error bubble up and keep the SW state in sync with
the hardware.

>> +				list_del(&mst->node);
>> +				kfree(mst);
>> +			}
>> +
>> +			return err;
>> +		}
>> +	}
>> +
>> +	return -ENOENT;
>> +}
>> +
>> +static int mv88e6xxx_sid_get(struct mv88e6xxx_chip *chip, struct net_device *br,
>> +			     u16 msti, u8 *sid)
>> +{
>> +	struct mv88e6xxx_mst *mst;
>> +	int err, i;
>> +
>> +	if (!br)
>> +		return 0;
>
> Is this condition possible?

Removing.

>> +
>> +	if (!mv88e6xxx_has_stu(chip))
>> +		return -EOPNOTSUPP;
>> +
>> +	list_for_each_entry(mst, &chip->msts, node) {
>> +		if (mst->br == br && mst->msti == msti) {
>> +			refcount_inc(&mst->refcnt);
>> +			*sid = mst->stu.sid;
>> +			return 0;
>> +		}
>> +	}
>> +
>> +	err = mv88e6xxx_sid_new(chip, sid);
>> +	if (err)
>> +		return err;
>> +
>> +	mst = kzalloc(sizeof(*mst), GFP_KERNEL);
>> +	if (!mst)
>> +		return -ENOMEM;
>
> This leaks the new SID.

I don't think so, the SID is just calculated based on what is in
chip->msts. However:

- The naming is bad. Will change.

>> +
>> +	INIT_LIST_HEAD(&mst->node);
>> +	refcount_set(&mst->refcnt, 1);
>> +	mst->br = br;
>> +	mst->msti = msti;
>> +	mst->stu.valid = true;
>> +	mst->stu.sid = *sid;
>> +
>> +	/* The bridge starts out all ports in the disabled state. But
>> +	 * a STU state of disabled means to go by the port-global
>> +	 * state. So we set all user port's initial state to blocking,
>> +	 * to match the bridge's behavior.
>> +	 */
>> +	for (i = 0; i < mv88e6xxx_num_ports(chip); i++)
>> +		mst->stu.state[i] = dsa_is_user_port(chip->ds, i) ?
>> +			MV88E6XXX_PORT_CTL0_STATE_BLOCKING :
>> +			MV88E6XXX_PORT_CTL0_STATE_DISABLED;
>> +
>> +	list_add_tail(&mst->node, &chip->msts);
>> +	return mv88e6xxx_stu_loadpurge(chip, &mst->stu);
>
> And this doesn't behave too well on failure (the MSTID exists in
> software but not in hardware).

Yes, fixing in v3.

>> +}
>> +
>> +static int mv88e6xxx_port_mst_state_set(struct dsa_switch *ds, int port,
>> +					const struct switchdev_mst_state *st)
>> +{
>> +	struct dsa_port *dp = dsa_to_port(ds, port);
>> +	struct mv88e6xxx_chip *chip = ds->priv;
>> +	struct mv88e6xxx_mst *mst;
>> +	u8 state;
>> +	int err;
>> +
>> +	if (!mv88e6xxx_has_stu(chip))
>> +		return -EOPNOTSUPP;
>> +
>> +	switch (st->state) {
>> +	case BR_STATE_DISABLED:
>> +	case BR_STATE_BLOCKING:
>> +	case BR_STATE_LISTENING:
>> +		state = MV88E6XXX_PORT_CTL0_STATE_BLOCKING;
>> +		break;
>> +	case BR_STATE_LEARNING:
>> +		state = MV88E6XXX_PORT_CTL0_STATE_LEARNING;
>> +		break;
>> +	case BR_STATE_FORWARDING:
>> +		state = MV88E6XXX_PORT_CTL0_STATE_FORWARDING;
>> +		break;
>> +	default:
>> +		return -EINVAL;
>> +	}
>> +
>> +	list_for_each_entry(mst, &chip->msts, node) {
>> +		if (mst->br == dsa_port_bridge_dev_get(dp) &&
>> +		    mst->msti == st->msti) {
>> +			if (mst->stu.state[port] == state)
>> +				return 0;
>> +
>> +			mst->stu.state[port] = state;
>> +			mv88e6xxx_reg_lock(chip);
>> +			err = mv88e6xxx_stu_loadpurge(chip, &mst->stu);
>> +			mv88e6xxx_reg_unlock(chip);
>> +			return err;
>> +		}
>> +	}
>> +
>> +	return -ENOENT;
>> +}
>> +
>>  static int mv88e6xxx_port_check_hw_vlan(struct dsa_switch *ds, int port,
>>  					u16 vid)
>>  {
>> @@ -2437,6 +2568,12 @@ static int mv88e6xxx_port_vlan_leave(struct mv88e6xxx_chip *chip,
>>  	if (err)
>>  		return err;
>>  
>> +	if (!vlan.valid && vlan.sid) {
>> +		err = mv88e6xxx_sid_put(chip, vlan.sid);
>> +		if (err)
>> +			return err;
>> +	}
>> +
>>  	return mv88e6xxx_g1_atu_remove(chip, vlan.fid, port, false);
>>  }
>>  
>> @@ -2482,6 +2619,44 @@ static int mv88e6xxx_port_vlan_del(struct dsa_switch *ds, int port,
>>  	return err;
>>  }
>>  
>> +static int mv88e6xxx_vlan_msti_set(struct dsa_switch *ds,
>> +				   const struct switchdev_attr *attr)
>> +{
>> +	const struct switchdev_vlan_attr *vattr = &attr->u.vlan_attr;
>> +	struct mv88e6xxx_chip *chip = ds->priv;
>> +	struct mv88e6xxx_vtu_entry vlan;
>> +	u8 new_sid;
>> +	int err;
>> +
>> +	mv88e6xxx_reg_lock(chip);
>> +
>> +	err = mv88e6xxx_vtu_get(chip, vattr->vid, &vlan);
>> +	if (err)
>> +		goto unlock;
>> +
>> +	if (!vlan.valid) {
>> +		err = -EINVAL;
>> +		goto unlock;
>> +	}
>> +
>> +	err = mv88e6xxx_sid_get(chip, attr->orig_dev, vattr->msti, &new_sid);
>> +	if (err)
>> +		goto unlock;
>> +
>> +	if (vlan.sid) {
>> +		err = mv88e6xxx_sid_put(chip, vlan.sid);
>> +		if (err)
>> +			goto unlock;
>> +	}
>> +
>> +	vlan.sid = new_sid;
>> +	err = mv88e6xxx_vtu_loadpurge(chip, &vlan);
>
> Maybe you could move mv88e6xxx_sid_put() after this succeeds?

Yep. Also made sure to avoid needless updates of the VTU entry if it
already belonged to the correct SID.

Thanks for the great review!