[PATCH RFC net-next 1/3] net: dsa: allow for multiple CPU ports

@@ -123,9 +123,10 @@ struct dsa_switch_tree {
 	struct dsa_platform_data	*pd;
 
 	/*
-	 * The switch port to which the CPU is attached.
+	 * The switch ports to which the CPU is attached.
 	 */
-	struct dsa_port		*cpu_dp;
+	size_t			num_cpu_dps;
+	struct dsa_port		*cpu_dps[DSA_MAX_PORTS];
 
 	/*
 	 * Data for the individual switch chips.

@@ -194,11 +194,12 @@ static bool dsa_tree_setup_routing_table(struct dsa_switch_tree *dst)
 	return complete;
 }
 
-static struct dsa_port *dsa_tree_find_first_cpu(struct dsa_switch_tree *dst)
+static void dsa_tree_fill_cpu_ports(struct dsa_switch_tree *dst)
 {
 	struct dsa_switch *ds;
 	struct dsa_port *dp;
 	int device, port;
+	int count = 0;
 
 	for (device = 0; device < DSA_MAX_SWITCHES; device++) {
 		ds = dst->ds[device];

@@ -208,28 +209,38 @@ static struct dsa_port *dsa_tree_find_first_cpu(struct dsa_switch_tree *dst)
 		for (port = 0; port < ds->num_ports; port++) {
 			dp = &ds->ports[port];
 
-			if (dsa_port_is_cpu(dp))
-				return dp;
+			if (dsa_port_is_cpu(dp)) {
+				if (count == ARRAY_SIZE(dst->cpu_dps)) {
+					pr_warn("Tree has too many CPU ports\n");
+					dst->num_cpu_dps = count;
+					return;
+				}
+
+				dst->cpu_dps[count++] = dp;
+			}
 		}
 	}
 
-	return NULL;
+	dst->num_cpu_dps = count;
 }
 
-static int dsa_tree_setup_default_cpu(struct dsa_switch_tree *dst)
+static int dsa_tree_setup_default_cpus(struct dsa_switch_tree *dst)
 {
 	struct dsa_switch *ds;
 	struct dsa_port *dp;
-	int device, port;
+	int device, port, i;
 
-	/* DSA currently only supports a single CPU port */
-	dst->cpu_dp = dsa_tree_find_first_cpu(dst);
-	if (!dst->cpu_dp) {
+	dsa_tree_fill_cpu_ports(dst);
+	if (!dst->num_cpu_dps) {
 		pr_warn("Tree has no master device\n");
 		return -EINVAL;
 	}
 
-	/* Assign the default CPU port to all ports of the fabric */
+	/* Assign the default CPU port to all ports of the fabric in a round
+	 * robin way. This should work nicely for all sane switch tree designs.
+	 */
+	i = 0;
+
 	for (device = 0; device < DSA_MAX_SWITCHES; device++) {
 		ds = dst->ds[device];
 		if (!ds)

@@ -238,18 +249,20 @@ static int dsa_tree_setup_default_cpu(struct dsa_switch_tree *dst)
 		for (port = 0; port < ds->num_ports; port++) {
 			dp = &ds->ports[port];
 
-			if (dsa_port_is_user(dp) || dsa_port_is_dsa(dp))
-				dp->cpu_dp = dst->cpu_dp;
+			if (dsa_port_is_user(dp) || dsa_port_is_dsa(dp)) {
+				dp->cpu_dp = dst->cpu_dps[i++];
+				if (i == dst->num_cpu_dps)
+					i = 0;
+			}
 		}
 	}
 
 	return 0;
 }
 
-static void dsa_tree_teardown_default_cpu(struct dsa_switch_tree *dst)
+static void dsa_tree_teardown_default_cpus(struct dsa_switch_tree *dst)
 {
-	/* DSA currently only supports a single CPU port */
-	dst->cpu_dp = NULL;
+	dst->num_cpu_dps = 0;
 }
 
 static int dsa_port_setup(struct dsa_port *dp)

@@ -493,21 +506,34 @@ static void dsa_tree_teardown_switches(struct dsa_switch_tree *dst)
 	}
 }
 
-static int dsa_tree_setup_master(struct dsa_switch_tree *dst)
+static int dsa_tree_setup_masters(struct dsa_switch_tree *dst)
 {
-	struct dsa_port *cpu_dp = dst->cpu_dp;
-	struct net_device *master = cpu_dp->master;
+	int i;
+	int err;
 
-	/* DSA currently supports a single pair of CPU port and master device */
-	return dsa_master_setup(master, cpu_dp);
+	for (i = 0; i < dst->num_cpu_dps; ++i) {
+		struct dsa_port *cpu_dp = dst->cpu_dps[i];
+		struct net_device *master = cpu_dp->master;
+
+		err = dsa_master_setup(master, cpu_dp);
+		if (err)
+			goto teardown;
+	}
+
+	return 0;
+teardown:
+	for (--i; i >= 0; --i)
+		dsa_master_teardown(dst->cpu_dps[i]->master);
+
+	return err;
 }
 
-static void dsa_tree_teardown_master(struct dsa_switch_tree *dst)
+static void dsa_tree_teardown_masters(struct dsa_switch_tree *dst)
 {
-	struct dsa_port *cpu_dp = dst->cpu_dp;
-	struct net_device *master = cpu_dp->master;
+	int i;
 
-	return dsa_master_teardown(master);
+	for (i = 0; i < dst->num_cpu_dps; ++i)
+		dsa_master_teardown(dst->cpu_dps[i]->master);
 }
 
 static int dsa_tree_setup(struct dsa_switch_tree *dst)

@@ -525,7 +551,7 @@ static int dsa_tree_setup(struct dsa_switch_tree *dst)
 	if (!complete)
 		return 0;
 
-	err = dsa_tree_setup_default_cpu(dst);
+	err = dsa_tree_setup_default_cpus(dst);
 	if (err)
 		return err;
 

@@ -533,7 +559,7 @@ static int dsa_tree_setup(struct dsa_switch_tree *dst)
 	if (err)
 		goto teardown_default_cpu;
 
-	err = dsa_tree_setup_master(dst);
+	err = dsa_tree_setup_masters(dst);
 	if (err)
 		goto teardown_switches;
 

@@ -546,7 +572,7 @@ static int dsa_tree_setup(struct dsa_switch_tree *dst)
 teardown_switches:
 	dsa_tree_teardown_switches(dst);
 teardown_default_cpu:
-	dsa_tree_teardown_default_cpu(dst);
+	dsa_tree_teardown_default_cpus(dst);
 
 	return err;
 }

@@ -556,11 +582,11 @@ static void dsa_tree_teardown(struct dsa_switch_tree *dst)
 	if (!dst->setup)
 		return;
 
-	dsa_tree_teardown_master(dst);
+	dsa_tree_teardown_masters(dst);
 
 	dsa_tree_teardown_switches(dst);
 
-	dsa_tree_teardown_default_cpu(dst);
+	dsa_tree_teardown_default_cpus(dst);
 
 	pr_info("DSA: tree %d torn down\n", dst->index);