Allow for multiple CPU ports in a DSA switch tree. By default the first
CPU port is assigned mimic the original assignement logic. A DSA driver
can define a function to declare a preferred CPU port based on the
provided port. If the function doesn't have a preferred port the CPU
port is assigned using a round-robin way starting from the last assigned
CPU port.
Examples:
There are two CPU port but no port_get_preferred_cpu is provided:
- The old logic is used. Every port is assigned to the first cpu port.
There are two CPU port but the port_get_preferred_cpu return -1:
- The port is assigned using a round-robin way since no preference is
  provided.
There are two CPU port and the port_get_preferred_cpu define only one
port and the rest with -1: (wan port with CPU1 and the rest no
preference)
  lan1 <-> eth0
  lan2 <-> eth1
  lan3 <-> eth0
  lan4 <-> eth1
  wan  <-> eth1
There are two CPU port and the port_get_preferred assign a preference
for every port: (wan port with CPU1 everything else CPU0)
  lan1 <-> eth0
  lan2 <-> eth0
  lan3 <-> eth0
  lan4 <-> eth0
  wan  <-> eth1

Signed-off-by: Marek BehĂșn <marek.be...@nic.cz>
Signed-off-by: Ansuel Smith <ansuels...@gmail.com>
---
 include/net/dsa.h |  7 +++++
 net/dsa/dsa2.c    | 66 +++++++++++++++++++++++++++++++++--------------
 2 files changed, 54 insertions(+), 19 deletions(-)

diff --git a/include/net/dsa.h b/include/net/dsa.h
index d71b1acd9c3e..3d3e936bda4c 100644
--- a/include/net/dsa.h
+++ b/include/net/dsa.h
@@ -523,6 +523,13 @@ struct dsa_switch_ops {
        void    (*teardown)(struct dsa_switch *ds);
        u32     (*get_phy_flags)(struct dsa_switch *ds, int port);
 
+       /*
+        * Get preferred CPU port for the provided port.
+        * Return -1 if there isn't a preferred CPU port, a round-robin logic
+        * is used to chose the CPU port to link to the provided port.
+        */
+       int     (*port_get_preferred_cpu)(struct dsa_switch *ds, int port);
+
        /*
         * Access to the switch's PHY registers.
         */
diff --git a/net/dsa/dsa2.c b/net/dsa/dsa2.c
index d142eb2b288b..d3b92499f006 100644
--- a/net/dsa/dsa2.c
+++ b/net/dsa/dsa2.c
@@ -315,10 +315,17 @@ 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 struct dsa_port *dsa_tree_find_next_cpu_port(struct dsa_switch_tree 
*dst,
+                                                   struct dsa_port *cpu_dp)
 {
-       struct dsa_port *dp;
+       struct dsa_port *dp = cpu_dp;
+
+       if (dp)
+               list_for_each_entry_from(dp, &dst->ports, list)
+                       if (dsa_port_is_cpu(dp))
+                               return dp;
 
+       /* If another CPU port can't be found, try from the start */
        list_for_each_entry(dp, &dst->ports, list)
                if (dsa_port_is_cpu(dp))
                        return dp;
@@ -326,25 +333,40 @@ static struct dsa_port *dsa_tree_find_first_cpu(struct 
dsa_switch_tree *dst)
        return NULL;
 }
 
-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_port *cpu_dp, *dp;
+       struct dsa_port *dp, *cpu_dp = NULL, *first_cpu_dp;
+       int cpu_port;
 
-       cpu_dp = dsa_tree_find_first_cpu(dst);
-       if (!cpu_dp) {
+       first_cpu_dp = dsa_tree_find_next_cpu_port(dst, NULL);
+       if (!first_cpu_dp) {
                pr_err("DSA: tree %d has no CPU port\n", dst->index);
                return -EINVAL;
        }
 
-       /* Assign the default CPU port to all ports of the fabric */
        list_for_each_entry(dp, &dst->ports, list)
-               if (dsa_port_is_user(dp) || dsa_port_is_dsa(dp))
-                       dp->cpu_dp = cpu_dp;
+               if (dsa_port_is_user(dp) || dsa_port_is_dsa(dp)) {
+                       /* Check if the driver advice a CPU port for the 
current port */
+                       if (dp->ds->ops->port_get_preferred_cpu) {
+                               cpu_port = 
dp->ds->ops->port_get_preferred_cpu(dp->ds, dp->index);
+
+                               /* If the driver doesn't have a preferred port,
+                                * assing in round-robin way.
+                                */
+                               if (cpu_port < 0)
+                                       cpu_dp = 
dsa_tree_find_next_cpu_port(dst, cpu_dp);
+                               else
+                                       cpu_dp = dsa_to_port(dp->ds, cpu_port);
+                       }
+
+                       /* If a cpu port is not chosen, assign the first one by 
default */
+                       dp->cpu_dp = cpu_dp ? cpu_dp : first_cpu_dp;
+               }
 
        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)
 {
        struct dsa_port *dp;
 
@@ -822,7 +844,7 @@ static void dsa_tree_teardown_switches(struct 
dsa_switch_tree *dst)
                dsa_switch_teardown(dp->ds);
 }
 
-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 *dp;
        int err;
@@ -831,14 +853,20 @@ static int dsa_tree_setup_master(struct dsa_switch_tree 
*dst)
                if (dsa_port_is_cpu(dp)) {
                        err = dsa_master_setup(dp->master, dp);
                        if (err)
-                               return err;
+                               goto teardown;
                }
        }
 
        return 0;
+teardown:
+       list_for_each_entry_from_reverse(dp, &dst->ports, list)
+               if (dsa_port_is_cpu(dp))
+                       dsa_master_teardown(dp->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 *dp;
 
@@ -888,7 +916,7 @@ 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;
 
@@ -896,7 +924,7 @@ 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;
 
@@ -911,11 +939,11 @@ static int dsa_tree_setup(struct dsa_switch_tree *dst)
        return 0;
 
 teardown_master:
-       dsa_tree_teardown_master(dst);
+       dsa_tree_teardown_masters(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;
 }
@@ -929,11 +957,11 @@ static void dsa_tree_teardown(struct dsa_switch_tree *dst)
 
        dsa_tree_teardown_lags(dst);
 
-       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);
 
        list_for_each_entry_safe(dl, next, &dst->rtable, list) {
                list_del(&dl->list);
-- 
2.30.2

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