net: dsa: list DSA links in the fabric

Implement a new list of DSA links in the switch fabric itself, to
provide an alterative to the ds->rtable static arrays.

At the same time, provide a new dsa_routing_port() helper to abstract
the usage of ds->rtable in drivers. If there's no port to reach a
given device, return the first invalid port, ds->num_ports. This avoids
potential signedness errors or the need to define special values.

Signed-off-by: Vivien Didelot <vivien.didelot@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>

drivers/net/dsa/mv88e6xxx/chip.c

@@ -1143,6 +1143,7 @@ static int mv88e6xxx_pri_setup(struct mv88e6xxx_chip *chip)
 
 static int mv88e6xxx_devmap_setup(struct mv88e6xxx_chip *chip)
 {
+	struct dsa_switch *ds = chip->ds;
 	int target, port;
 	int err;
 
@@ -1151,10 +1152,9 @@ static int mv88e6xxx_devmap_setup(struct mv88e6xxx_chip *chip)
 
 	/* Initialize the routing port to the 32 possible target devices */
 	for (target = 0; target < 32; target++) {
-		port = 0x1f;
-		if (target < DSA_MAX_SWITCHES)
-			if (chip->ds->rtable[target] != DSA_RTABLE_NONE)
-				port = chip->ds->rtable[target];
+		port = dsa_routing_port(ds, target);
+		if (port == ds->num_ports)
+			port = 0x1f;
 
 		err = mv88e6xxx_g2_device_mapping_write(chip, target, port);
 		if (err)

include/net/dsa.h

@@ -127,6 +127,9 @@ struct dsa_switch_tree {
 	/* List of switch ports */
 	struct list_head ports;
 
+	/* List of DSA links composing the routing table */
+	struct list_head rtable;
+
 	/*
 	 * Data for the individual switch chips.
 	 */
@@ -225,6 +228,17 @@ struct dsa_port {
 	bool setup;
 };
 
+/* TODO: ideally DSA ports would have a single dp->link_dp member,
+ * and no dst->rtable nor this struct dsa_link would be needed,
+ * but this would require some more complex tree walking,
+ * so keep it stupid at the moment and list them all.
+ */
+struct dsa_link {
+	struct dsa_port *dp;
+	struct dsa_port *link_dp;
+	struct list_head list;
+};
+
 struct dsa_switch {
 	bool setup;
 
@@ -341,14 +355,27 @@ static inline u32 dsa_user_ports(struct dsa_switch *ds)
 	return mask;
 }
 
+/* Return the local port used to reach an arbitrary switch device */
+static inline unsigned int dsa_routing_port(struct dsa_switch *ds, int device)
+{
+	struct dsa_switch_tree *dst = ds->dst;
+	struct dsa_link *dl;
+
+	list_for_each_entry(dl, &dst->rtable, list)
+		if (dl->dp->ds == ds && dl->link_dp->ds->index == device)
+			return dl->dp->index;
+
+	return ds->num_ports;
+}
+
 /* Return the local port used to reach an arbitrary switch port */
 static inline unsigned int dsa_towards_port(struct dsa_switch *ds, int device,
 					    int port)
 {
 	if (device == ds->index)
 		return port;
 	else
-		return ds->rtable[device];
+		return dsa_routing_port(ds, device);
 }
 
 /* Return the local port used to reach the dedicated CPU port */

net/dsa/dsa2.c

@@ -45,6 +45,8 @@ static struct dsa_switch_tree *dsa_tree_alloc(int index)
 
 	dst->index = index;
 
+	INIT_LIST_HEAD(&dst->rtable);
+
 	INIT_LIST_HEAD(&dst->ports);
 
 	INIT_LIST_HEAD(&dst->list);
@@ -122,13 +124,39 @@ static struct dsa_port *dsa_tree_find_port_by_node(struct dsa_switch_tree *dst,
 	return NULL;
 }
 
+struct dsa_link *dsa_link_touch(struct dsa_port *dp, struct dsa_port *link_dp)
+{
+	struct dsa_switch *ds = dp->ds;
+	struct dsa_switch_tree *dst;
+	struct dsa_link *dl;
+
+	dst = ds->dst;
+
+	list_for_each_entry(dl, &dst->rtable, list)
+		if (dl->dp == dp && dl->link_dp == link_dp)
+			return dl;
+
+	dl = kzalloc(sizeof(*dl), GFP_KERNEL);
+	if (!dl)
+		return NULL;
+
+	dl->dp = dp;
+	dl->link_dp = link_dp;
+
+	INIT_LIST_HEAD(&dl->list);
+	list_add_tail(&dl->list, &dst->rtable);
+
+	return dl;
+}
+
 static bool dsa_port_setup_routing_table(struct dsa_port *dp)
 {
 	struct dsa_switch *ds = dp->ds;
 	struct dsa_switch_tree *dst = ds->dst;
 	struct device_node *dn = dp->dn;
 	struct of_phandle_iterator it;
 	struct dsa_port *link_dp;
+	struct dsa_link *dl;
 	int err;
 
 	of_for_each_phandle(&it, err, dn, "link", NULL, 0) {
@@ -138,7 +166,11 @@ static bool dsa_port_setup_routing_table(struct dsa_port *dp)
 			return false;
 		}
 
-		ds->rtable[link_dp->ds->index] = dp->index;
+		dl = dsa_link_touch(dp, link_dp);
+		if (!dl) {
+			of_node_put(it.node);
+			return false;
+		}
 	}
 
 	return true;
@@ -548,6 +580,8 @@ static int dsa_tree_setup(struct dsa_switch_tree *dst)
 
 static void dsa_tree_teardown(struct dsa_switch_tree *dst)
 {
+	struct dsa_link *dl, *next;
+
 	if (!dst->setup)
 		return;
 
@@ -557,6 +591,11 @@ static void dsa_tree_teardown(struct dsa_switch_tree *dst)
 
 	dsa_tree_teardown_default_cpu(dst);
 
+	list_for_each_entry_safe(dl, next, &dst->rtable, list) {
+		list_del(&dl->list);
+		kfree(dl);
+	}
+
 	pr_info("DSA: tree %d torn down\n", dst->index);
 
 	dst->setup = false;