Re: [net-next RFC PATCH v4 01/15] net: dsa: provide switch operations for tracking the master state

[Florian Fainelli <f.fainelli@gmail.com>]

On 12/11/2021 11:57 AM, Ansuel Smith wrote:
> From: Vladimir Oltean <vladimir.oltean@nxp.com>
> 
> Certain drivers may need to send management traffic to the switch for
> things like register access, FDB dump, etc, to accelerate what their
> slow bus (SPI, I2C, MDIO) can already do.
> 
> Ethernet is faster (especially in bulk transactions) but is also more
> unreliable, since the user may decide to bring the DSA master down (or
> not bring it up), therefore severing the link between the host and the
> attached switch.
> 
> Drivers needing Ethernet-based register access already should have
> fallback logic to the slow bus if the Ethernet method fails, but that
> fallback may be based on a timeout, and the I/O to the switch may slow
> down to a halt if the master is down, because every Ethernet packet will
> have to time out. The driver also doesn't have the option to turn off
> Ethernet-based I/O momentarily, because it wouldn't know when to turn it
> back on.
> 
> Which is where this change comes in. By tracking NETDEV_CHANGE,
> NETDEV_UP and NETDEV_GOING_DOWN events on the DSA master, we should know
> the exact interval of time during which this interface is reliably
> available for traffic. Provide this information to switches so they can
> use it as they wish.
> 
> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
> Signed-off-by: Ansuel Smith <ansuelsmth@gmail.com>
> ---
>   include/net/dsa.h  | 11 +++++++++++
>   net/dsa/dsa2.c     | 46 ++++++++++++++++++++++++++++++++++++++++++++++
>   net/dsa/dsa_priv.h | 13 +++++++++++++
>   net/dsa/slave.c    | 32 ++++++++++++++++++++++++++++++++
>   net/dsa/switch.c   | 15 +++++++++++++++
>   5 files changed, 117 insertions(+)
> 
> diff --git a/include/net/dsa.h b/include/net/dsa.h
> index 8b496c7e62ef..12352aafe1cf 100644
> --- a/include/net/dsa.h
> +++ b/include/net/dsa.h
> @@ -299,6 +299,10 @@ struct dsa_port {
>   	struct list_head	fdbs;
>   	struct list_head	mdbs;
>   
> +	/* Master state bits, valid only on CPU ports */
> +	u8 master_admin_up:1,
> +	   master_oper_up:1;
> +
>   	bool setup;
>   };
>   
> @@ -1023,6 +1027,13 @@ struct dsa_switch_ops {
>   	int	(*tag_8021q_vlan_add)(struct dsa_switch *ds, int port, u16 vid,
>   				      u16 flags);
>   	int	(*tag_8021q_vlan_del)(struct dsa_switch *ds, int port, u16 vid);
> +
> +	/*
> +	 * DSA master tracking operations
> +	 */
> +	void	(*master_state_change)(struct dsa_switch *ds,
> +				       const struct net_device *master,
> +				       bool operational);
>   };
>   
>   #define DSA_DEVLINK_PARAM_DRIVER(_id, _name, _type, _cmodes)		\
> diff --git a/net/dsa/dsa2.c b/net/dsa/dsa2.c
> index cf6566168620..86b1e2f11469 100644
> --- a/net/dsa/dsa2.c
> +++ b/net/dsa/dsa2.c
> @@ -1245,6 +1245,52 @@ int dsa_tree_change_tag_proto(struct dsa_switch_tree *dst,
>   	return err;
>   }
>   
> +static void dsa_tree_master_state_change(struct dsa_switch_tree *dst,
> +					 struct net_device *master)
> +{
> +	struct dsa_notifier_master_state_info info;
> +	struct dsa_port *cpu_dp = master->dsa_ptr;
> +
> +	info.master = master;
> +	info.operational = cpu_dp->master_admin_up && cpu_dp->master_oper_up;

Since this gets tested a few times below, I would be tempted to add a:

dsa_master_is_operational() helper and use it throughout.

> +
> +	dsa_tree_notify(dst, DSA_NOTIFIER_MASTER_STATE_CHANGE, &info);
> +}
> +
> +void dsa_tree_master_admin_state_change(struct dsa_switch_tree *dst,
> +					struct net_device *master,
> +					bool up)
> +{
> +	struct dsa_port *cpu_dp = master->dsa_ptr;
> +	bool notify = false;
> +
> +	if ((cpu_dp->master_admin_up && cpu_dp->master_oper_up) !=

Here

> +	    (up && cpu_dp->master_oper_up))
> +		notify = true;
> +
> +	cpu_dp->master_admin_up = up;
> +
> +	if (notify)
> +		dsa_tree_master_state_change(dst, master);
> +}
> +
> +void dsa_tree_master_oper_state_change(struct dsa_switch_tree *dst,
> +				       struct net_device *master,
> +				       bool up)
> +{
> +	struct dsa_port *cpu_dp = master->dsa_ptr;
> +	bool notify = false;
> +
> +	if ((cpu_dp->master_admin_up && cpu_dp->master_oper_up) !=

And here as well

> +	    (cpu_dp->master_admin_up && up))
> +		notify = true;
> +
> +	cpu_dp->master_oper_up = up;
> +
> +	if (notify)
> +		dsa_tree_master_state_change(dst, master);
> +}
> +
>   static struct dsa_port *dsa_port_touch(struct dsa_switch *ds, int index)
>   {
>   	struct dsa_switch_tree *dst = ds->dst;
> diff --git a/net/dsa/dsa_priv.h b/net/dsa/dsa_priv.h
> index 0db2b26b0c83..d2f2bce2391b 100644
> --- a/net/dsa/dsa_priv.h
> +++ b/net/dsa/dsa_priv.h
> @@ -44,6 +44,7 @@ enum {
>   	DSA_NOTIFIER_MRP_DEL_RING_ROLE,
>   	DSA_NOTIFIER_TAG_8021Q_VLAN_ADD,
>   	DSA_NOTIFIER_TAG_8021Q_VLAN_DEL,
> +	DSA_NOTIFIER_MASTER_STATE_CHANGE,
>   };
>   
>   /* DSA_NOTIFIER_AGEING_TIME */
> @@ -127,6 +128,12 @@ struct dsa_notifier_tag_8021q_vlan_info {
>   	u16 vid;
>   };
>   
> +/* DSA_NOTIFIER_MASTER_STATE_CHANGE */
> +struct dsa_notifier_master_state_info {
> +	const struct net_device *master;
> +	bool operational;
> +};
> +
>   struct dsa_switchdev_event_work {
>   	struct dsa_switch *ds;
>   	int port;
> @@ -507,6 +514,12 @@ int dsa_tree_change_tag_proto(struct dsa_switch_tree *dst,
>   			      struct net_device *master,
>   			      const struct dsa_device_ops *tag_ops,
>   			      const struct dsa_device_ops *old_tag_ops);
> +void dsa_tree_master_admin_state_change(struct dsa_switch_tree *dst,
> +					struct net_device *master,
> +					bool up);
> +void dsa_tree_master_oper_state_change(struct dsa_switch_tree *dst,
> +				       struct net_device *master,
> +				       bool up);
>   unsigned int dsa_bridge_num_get(const struct net_device *bridge_dev, int max);
>   void dsa_bridge_num_put(const struct net_device *bridge_dev,
>   			unsigned int bridge_num);
> diff --git a/net/dsa/slave.c b/net/dsa/slave.c
> index 88f7b8686dac..5ccb0616022d 100644
> --- a/net/dsa/slave.c
> +++ b/net/dsa/slave.c
> @@ -2348,6 +2348,36 @@ static int dsa_slave_netdevice_event(struct notifier_block *nb,
>   		err = dsa_port_lag_change(dp, info->lower_state_info);
>   		return notifier_from_errno(err);
>   	}
> +	case NETDEV_CHANGE:
> +	case NETDEV_UP: {
> +		/* Track state of master port.
> +		 * DSA driver may require the master port (and indirectly
> +		 * the tagger) to be available for some special operation.
> +		 */
> +		if (netdev_uses_dsa(dev)) {
> +			struct dsa_port *cpu_dp = dev->dsa_ptr;
> +			struct dsa_switch_tree *dst = cpu_dp->ds->dst;
> +
> +			/* Track when the master port is UP */
> +			dsa_tree_master_oper_state_change(dst, dev,
> +							  netif_oper_up(dev));
> +
> +			/* Track when the master port is ready and can accept
> +			 * packet.
> +			 * NETDEV_UP event is not enough to flag a port as ready.
> +			 * We also have to wait for linkwatch_do_dev to dev_activate
> +			 * and emit a NETDEV_CHANGE event.
> +			 * We check if a master port is ready by checking if the dev
> +			 * have a qdisc assigned and is not noop.
> +			 */
> +			dsa_tree_master_admin_state_change(dst, dev,
> +							   qdisc_tx_is_noop(dev));

If my kernel is built with no packet scheduler, is not the interface 
going to be configured with noop all of the time?

Other than that LGTM!
-- 
Florian