netdev - Re: [PATCH v2 net-next 07/10] net: dsa: Pass MST state changes to driver

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Date:   Thu, 10 Mar 2022 09:54:34 +0100
From:   Tobias Waldekranz <tobias@...dekranz.com>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     davem@...emloft.net, kuba@...nel.org, Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Ivan Vecera <ivecera@...hat.com>,
        Roopa Prabhu <roopa@...dia.com>,
        Nikolay Aleksandrov <razor@...ckwall.org>,
        Russell King <linux@...linux.org.uk>,
        Petr Machata <petrm@...dia.com>,
        Cooper Lees <me@...perlees.com>,
        Ido Schimmel <idosch@...dia.com>,
        Matt Johnston <matt@...econstruct.com.au>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        bridge@...ts.linux-foundation.org
Subject: Re: [PATCH v2 net-next 07/10] net: dsa: Pass MST state changes to
 driver

On Fri, Mar 04, 2022 at 00:20, Vladimir Oltean <olteanv@...il.com> wrote:
> On Tue, Mar 01, 2022 at 11:03:18AM +0100, Tobias Waldekranz wrote:
>> Add the usual trampoline functionality from the generic DSA layer down
>> to the drivers for MST state changes.
>> 
>> Signed-off-by: Tobias Waldekranz <tobias@...dekranz.com>
>> ---
>>  include/net/dsa.h  |  2 ++
>>  net/dsa/dsa_priv.h |  2 ++
>>  net/dsa/port.c     | 30 ++++++++++++++++++++++++++++++
>>  net/dsa/slave.c    |  6 ++++++
>>  4 files changed, 40 insertions(+)
>> 
>> diff --git a/include/net/dsa.h b/include/net/dsa.h
>> index cc8acb01bd9b..096e6e3a8e1e 100644
>> --- a/include/net/dsa.h
>> +++ b/include/net/dsa.h
>> @@ -943,6 +943,8 @@ struct dsa_switch_ops {
>>  				     struct dsa_bridge bridge);
>>  	void	(*port_stp_state_set)(struct dsa_switch *ds, int port,
>>  				      u8 state);
>> +	int	(*port_mst_state_set)(struct dsa_switch *ds, int port,
>> +				      const struct switchdev_mst_state *state);
>>  	void	(*port_fast_age)(struct dsa_switch *ds, int port);
>>  	int	(*port_pre_bridge_flags)(struct dsa_switch *ds, int port,
>>  					 struct switchdev_brport_flags flags,
>> diff --git a/net/dsa/dsa_priv.h b/net/dsa/dsa_priv.h
>> index 87ec0697e92e..a620e079ebc5 100644
>> --- a/net/dsa/dsa_priv.h
>> +++ b/net/dsa/dsa_priv.h
>> @@ -198,6 +198,8 @@ static inline struct net_device *dsa_master_find_slave(struct net_device *dev,
>>  void dsa_port_set_tag_protocol(struct dsa_port *cpu_dp,
>>  			       const struct dsa_device_ops *tag_ops);
>>  int dsa_port_set_state(struct dsa_port *dp, u8 state, bool do_fast_age);
>> +int dsa_port_set_mst_state(struct dsa_port *dp,
>> +			   const struct switchdev_mst_state *state);
>>  int dsa_port_enable_rt(struct dsa_port *dp, struct phy_device *phy);
>>  int dsa_port_enable(struct dsa_port *dp, struct phy_device *phy);
>>  void dsa_port_disable_rt(struct dsa_port *dp);
>> diff --git a/net/dsa/port.c b/net/dsa/port.c
>> index 5f45cb7d70ba..26cfbc8ab499 100644
>> --- a/net/dsa/port.c
>> +++ b/net/dsa/port.c
>> @@ -108,6 +108,36 @@ int dsa_port_set_state(struct dsa_port *dp, u8 state, bool do_fast_age)
>>  	return 0;
>>  }
>>  
>> +int dsa_port_set_mst_state(struct dsa_port *dp,
>> +			   const struct switchdev_mst_state *state)
>> +{
>> +	struct dsa_switch *ds = dp->ds;
>> +	int err, port = dp->index;
>> +
>> +	if (!ds->ops->port_mst_state_set)
>> +		return -EOPNOTSUPP;
>> +
>> +	err = ds->ops->port_mst_state_set(ds, port, state);
>> +	if (err)
>> +		return err;
>> +
>> +	if (!dsa_port_can_configure_learning(dp) || dp->learning) {
>> +		switch (state->state) {
>> +		case BR_STATE_DISABLED:
>> +		case BR_STATE_BLOCKING:
>> +		case BR_STATE_LISTENING:
>> +			/* Ideally we would only fast age entries
>> +			 * belonging to VLANs controlled by this
>> +			 * MST.
>> +			 */
>> +			dsa_port_fast_age(dp);
>
> Does mv88e6xxx support this? If it does, you might just as well
> introduce another variant of ds->ops->port_fast_age() for an msti.

You can limit ATU operations to a particular FID. So the way I see it we
could either have:

int (*port_vlan_fast_age)(struct dsa_switch *ds, int port, u16 vid)

+ Maybe more generic. You could imagine there being a way to trigger
  this operation from userspace for example.
- We would have to keep the VLAN<->MSTI mapping in the DSA layer in
  order to be able to do the fan-out in dsa_port_set_mst_state.

or:

int (*port_msti_fast_age)(struct dsa_switch *ds, int port, u16 msti)

+ Let's the mapping be an internal affair in the driver.
- Perhaps, less generically useful.

Which one do you prefer? Or is there a hidden third option? :)

> And since it is new code, you could require that drivers _do_ support
> configuring learning before they could support MSTP. After all, we don't
> want to keep legacy mechanisms in place forever.

By "configuring learning", do you mean this new fast-age-per-vid/msti,
or being able to enable/disable learning per port? If it's the latter,
I'm not sure I understand how those two are related.