of: provide a binding for fixed link PHYs

Some Ethernet MACs have a "fixed link", and are not connected to a
normal MDIO-managed PHY device. For those situations, a Device Tree
binding allows to describe a "fixed link" using a special PHY node.

This patch adds:

 * A documentation for the fixed PHY Device Tree binding.

 * An of_phy_is_fixed_link() function that an Ethernet driver can call
   on its PHY phandle to find out whether it's a fixed link PHY or
   not. It should typically be used to know if
   of_phy_register_fixed_link() should be called.

 * An of_phy_register_fixed_link() function that instantiates the
   fixed PHY into the PHY subsystem, so that when the driver calls
   of_phy_connect(), the PHY device associated to the OF node will be
   found.

These two additional functions also support the old fixed-link Device
Tree binding used on PowerPC platforms, so that ultimately, the
network device drivers for those platforms could be converted to use
of_phy_is_fixed_link() and of_phy_register_fixed_link() instead of
of_phy_connect_fixed_link(), while keeping compatibility with their
respective Device Tree bindings.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Tested-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/devicetree/bindings/net/fixed-link.txt

@@ -0,0 +1,30 @@
+Fixed link Device Tree binding
+------------------------------
+
+Some Ethernet MACs have a "fixed link", and are not connected to a
+normal MDIO-managed PHY device. For those situations, a Device Tree
+binding allows to describe a "fixed link".
+
+Such a fixed link situation is described by creating a 'fixed-link'
+sub-node of the Ethernet MAC device node, with the following
+properties:
+
+* 'speed' (integer, mandatory), to indicate the link speed. Accepted
+  values are 10, 100 and 1000
+* 'full-duplex' (boolean, optional), to indicate that full duplex is
+  used. When absent, half duplex is assumed.
+* 'pause' (boolean, optional), to indicate that pause should be
+  enabled.
+* 'asym-pause' (boolean, optional), to indicate that asym_pause should
+  be enabled.
+
+Example:
+
+ethernet@0 {
+	...
+	fixed-link {
+	      speed = <1000>;
+	      full-duplex;
+	};
+	...
+};

drivers/of/of_mdio.c

@@ -14,6 +14,7 @@
 #include <linux/netdevice.h>
 #include <linux/err.h>
 #include <linux/phy.h>
+#include <linux/phy_fixed.h>
 #include <linux/of.h>
 #include <linux/of_irq.h>
 #include <linux/of_mdio.h>
@@ -301,3 +302,69 @@ struct phy_device *of_phy_attach(struct net_device *dev,
 	return phy_attach_direct(dev, phy, flags, iface) ? NULL : phy;
 }
 EXPORT_SYMBOL(of_phy_attach);
+
+#if defined(CONFIG_FIXED_PHY)
+/*
+ * of_phy_is_fixed_link() and of_phy_register_fixed_link() must
+ * support two DT bindings:
+ * - the old DT binding, where 'fixed-link' was a property with 5
+ *   cells encoding various informations about the fixed PHY
+ * - the new DT binding, where 'fixed-link' is a sub-node of the
+ *   Ethernet device.
+ */
+bool of_phy_is_fixed_link(struct device_node *np)
+{
+	struct device_node *dn;
+	int len;
+
+	/* New binding */
+	dn = of_get_child_by_name(np, "fixed-link");
+	if (dn) {
+		of_node_put(dn);
+		return true;
+	}
+
+	/* Old binding */
+	if (of_get_property(np, "fixed-link", &len) &&
+	    len == (5 * sizeof(__be32)))
+		return true;
+
+	return false;
+}
+EXPORT_SYMBOL(of_phy_is_fixed_link);
+
+int of_phy_register_fixed_link(struct device_node *np)
+{
+	struct fixed_phy_status status = {};
+	struct device_node *fixed_link_node;
+	const __be32 *fixed_link_prop;
+	int len;
+
+	/* New binding */
+	fixed_link_node = of_get_child_by_name(np, "fixed-link");
+	if (fixed_link_node) {
+		status.link = 1;
+		status.duplex = of_property_read_bool(np, "full-duplex");
+		if (of_property_read_u32(fixed_link_node, "speed", &status.speed))
+			return -EINVAL;
+		status.pause = of_property_read_bool(np, "pause");
+		status.asym_pause = of_property_read_bool(np, "asym-pause");
+		of_node_put(fixed_link_node);
+		return fixed_phy_register(PHY_POLL, &status, np);
+	}
+
+	/* Old binding */
+	fixed_link_prop = of_get_property(np, "fixed-link", &len);
+	if (fixed_link_prop && len == (5 * sizeof(__be32))) {
+		status.link = 1;
+		status.duplex = be32_to_cpu(fixed_link_prop[1]);
+		status.speed = be32_to_cpu(fixed_link_prop[2]);
+		status.pause = be32_to_cpu(fixed_link_prop[3]);
+		status.asym_pause = be32_to_cpu(fixed_link_prop[4]);
+		return fixed_phy_register(PHY_POLL, &status, np);
+	}
+
+	return -ENODEV;
+}
+EXPORT_SYMBOL(of_phy_register_fixed_link);
+#endif

include/linux/of_mdio.h

@@ -72,4 +72,19 @@ static inline struct mii_bus *of_mdio_find_bus(struct device_node *mdio_np)
 }
 #endif /* CONFIG_OF */
 
+#if defined(CONFIG_OF) && defined(CONFIG_FIXED_PHY)
+extern int of_phy_register_fixed_link(struct device_node *np);
+extern bool of_phy_is_fixed_link(struct device_node *np);
+#else
+static inline int of_phy_register_fixed_link(struct device_node *np)
+{
+	return -ENOSYS;
+}
+static inline bool of_phy_is_fixed_link(struct device_node *np)
+{
+	return false;
+}
+#endif
+
+
 #endif /* __LINUX_OF_MDIO_H */