dsa: Support multiple MDIO busses

This change “dsa: Support multiple MDIO busses” in Linux kernel is authored by Andrew Lunn <andrew [at] lunn.ch> on Sat Aug 8 17:09:14 2015 +0200.

dsa: Support multiple MDIO busses

When using a cluster of switches, some topologies will have an MDIO
bus per switch, not one for the whole cluster. Allow this to be
represented in the device tree, by adding an optional mii-bus property
at the switch level. The old platform_device method of instantiation
supports this already, so only the device tree binding needs extending
with an additional optional phandle.

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

This Linux change may have been applied to various maintained Linux releases and you can find Linux releases including commit 6bc6d0a.

There are 17 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 Documentation/devicetree/bindings/net/dsa/dsa.txt |  5 +++++
 net/dsa/dsa.c                                     | 12 +++++++++++-
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/net/dsa/dsa.txt b/Documentation/devicetree/bindings/net/dsa/dsa.txt
index f0b4cd7..9cf9a0e 100644
--- a/Documentation/devicetree/bindings/net/dsa/dsa.txt
+++ b/Documentation/devicetree/bindings/net/dsa/dsa.txt
@@ -58,6 +58,10 @@ Optionnal property:
 			  Documentation/devicetree/bindings/net/ethernet.txt
 			  for details.
 
+- mii-bus		: Should be a phandle to a valid MDIO bus device node.
+			  This mii-bus will be used in preference to the
+			  global dsa,mii-bus defined above, for this switch.
+
 Optional subnodes:
 - fixed-link		: Fixed-link subnode describing a link to a non-MDIO
 			  managed entity. See
@@ -107,6 +111,7 @@ Example:
 			#address-cells = <1>;
 			#size-cells = <0>;
 			reg = <17 1>;	/* MDIO address 17, switch 1 in tree */
+			mii-bus = <&mii_bus1>;
 
 			switch1uplink: port@0 {
 				reg = <0>;
diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c
index b445d49..78d4ac9 100644
--- a/net/dsa/dsa.c
+++ b/net/dsa/dsa.c
@@ -574,7 +574,7 @@ static int dsa_of_probe(struct device *dev)
 {
 	struct device_node *np = dev->of_node;
 	struct device_node *child, *mdio, *ethernet, *port, *link;
-	struct mii_bus *mdio_bus;
+	struct mii_bus *mdio_bus, *mdio_bus_switch;
 	struct net_device *ethernet_dev;
 	struct dsa_platform_data *pd;
 	struct dsa_chip_data *cd;
@@ -636,6 +636,16 @@ static int dsa_of_probe(struct device *dev)
 		if (!of_property_read_u32(child, "eeprom-length", &eeprom_len))
 			cd->eeprom_len = eeprom_len;
 
+		mdio = of_parse_phandle(child, "mii-bus", 0);
+		if (mdio) {
+			mdio_bus_switch = of_mdio_find_bus(mdio);
+			if (!mdio_bus_switch) {
+				ret = -EPROBE_DEFER;
+				goto out_free_chip;
+			}
+			cd->host_dev = &mdio_bus_switch->dev;
+		}
+
 		for_each_available_child_of_node(child, port) {
 			port_reg = of_get_property(port, "reg", NULL);
 			if (!port_reg)

The commit for this change in Linux stable tree is 6bc6d0a (patch).

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