net: dsa: fix filling routing table from OF description

According to description in 'include/net/dsa.h', in cascade switches
configurations where there are more than one interconnected devices,
'rtable' array in 'dsa_chip_data' structure is used to indicate which
port on this switch should be used to send packets to that are destined
for corresponding switch.

However, dsa_of_setup_routing_table() fills 'rtable' with port numbers
of the _target_ switch, but not current one.

This commit removes redundant devicetree parsing and adds needed port
number as a function argument. So dsa_of_setup_routing_table() now just
looks for target switch number by parsing parent of 'link' device node.

To remove possible misunderstandings with the way of determining target
switch number, a corresponding comment was added to the source code and
to the DSA device tree bindings documentation file.

This was tested on a custom board with two Marvell 88E6095 switches with
following corresponding routing tables: { -1, 10 } and { 8, -1 }.

Signed-off-by: Pavel Nakonechny <pavel.nakonechny@skitlab.ru>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 10 insertions, 17 deletions

diff --git a/Documentation/devicetree/bindings/net/dsa/dsa.txt b/Documentation/devicetree/bindings/net/dsa/dsa.txt
index e124847443f8..f0b4cd72411d 100644
--- a/Documentation/devicetree/bindings/net/dsa/dsa.txt
+++ b/Documentation/devicetree/bindings/net/dsa/dsa.txt
@@ -19,7 +19,9 @@ the parent DSA node. The maximum number of allowed child nodes is 4
 (DSA_MAX_SWITCHES).
 Each of these switch child nodes should have the following required properties:
 
-- reg                   : Describes the switch address on the MII bus
+- reg                   : Contains two fields. The first one describes the
+                          address on the MII bus. The second is the switch
+                          number that must be unique in cascaded configurations
 - #address-cells        : Must be 1
 - #size-cells           : Must be 0
 
diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c
index 2173402d87e0..4dea2e0681d1 100644
--- a/net/dsa/dsa.c
+++ b/net/dsa/dsa.c
@@ -501,12 +501,10 @@ static struct net_device *dev_to_net_device(struct device *dev)
 #ifdef CONFIG_OF
 static int dsa_of_setup_routing_table(struct dsa_platform_data *pd,
                                         struct dsa_chip_data *cd,
-                                        int chip_index,
+                                        int chip_index, int port_index,
                                         struct device_node *link)
 {
-        int ret;
         const __be32 *reg;
-        int link_port_addr;
         int link_sw_addr;
         struct device_node *parent_sw;
         int len;
@@ -519,6 +517,10 @@ static int dsa_of_setup_routing_table(struct dsa_platform_data *pd,
         if (!reg || (len != sizeof(*reg) * 2))
                 return -EINVAL;
 
+        /*
+         * Get the destination switch number from the second field of its 'reg'
+         * property, i.e. for "reg = <0x19 1>" sw_addr is '1'.
+         */
         link_sw_addr = be32_to_cpup(reg + 1);
 
         if (link_sw_addr >= pd->nr_chips)
@@ -535,20 +537,9 @@ static int dsa_of_setup_routing_table(struct dsa_platform_data *pd,
                 memset(cd->rtable, -1, pd->nr_chips * sizeof(s8));
         }
 
-        reg = of_get_property(link, "reg", NULL);
-        if (!reg) {
-                ret = -EINVAL;
-                goto out;
-        }
-
-        link_port_addr = be32_to_cpup(reg);
-
-        cd->rtable[link_sw_addr] = link_port_addr;
+        cd->rtable[link_sw_addr] = port_index;
 
         return 0;
-out:
-        kfree(cd->rtable);
-        return ret;
 }
 
 static void dsa_of_free_platform_data(struct dsa_platform_data *pd)
@@ -658,7 +649,7 @@ static int dsa_of_probe(struct platform_device *pdev)
                         if (!strcmp(port_name, "dsa") && link &&
                                         pd->nr_chips > 1) {
                                 ret = dsa_of_setup_routing_table(pd, cd,
-                                                chip_index, link);
+                                                chip_index, port_index, link);
                                 if (ret)
                                         goto out_free_chip;
                         }