netdev/of/phy: Add MDIO bus multiplexer support.

This patch adds a somewhat generic framework for MDIO bus
multiplexers.  It is modeled on the I2C multiplexer.

The multiplexer is needed if there are multiple PHYs with the same
address connected to the same MDIO bus adepter, or if there is
insufficient electrical drive capability for all the connected PHY
devices.

Conceptually it could look something like this:

                   ------------------
                   | Control Signal |
                   --------+---------
                           |
 ---------------   --------+------
 | MDIO MASTER |---| Multiplexer |
 ---------------   --+-------+----
                     |       |
                     C       C
                     h       h
                     i       i
                     l       l
                     d       d
                     |       |
     ---------       A       B   ---------
     |       |       |       |   |       |
     | PHY@1 +-------+       +---+ PHY@1 |
     |       |       |       |   |       |
     ---------       |       |   ---------
     ---------       |       |   ---------
     |       |       |       |   |       |
     | PHY@2 +-------+       +---+ PHY@2 |
     |       |                   |       |
     ---------                   ---------

This framework configures the bus topology from device tree data.  The
mechanics of switching the multiplexer is left to device specific
drivers.

The follow-on patch contains a multiplexer driven by GPIO lines.

Signed-off-by: David Daney <david.daney@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 202 insertions, 0 deletions

diff --git a/drivers/net/phy/Kconfig b/drivers/net/phy/Kconfig
index 0e01f4e5cd64..99c0674a5935 100644
--- a/drivers/net/phy/Kconfig
+++ b/drivers/net/phy/Kconfig
@@ -135,6 +135,15 @@ config MDIO_OCTEON
 
 	  If in doubt, say Y.
 
+config MDIO_BUS_MUX
+	tristate
+	depends on OF_MDIO
+	help
+	  This module provides a driver framework for MDIO bus
+	  multiplexers which connect one of several child MDIO busses
+	  to a parent bus.  Switching between child busses is done by
+	  device specific drivers.
+
 endif # PHYLIB
 
 config MICREL_KS8995MA
diff --git a/drivers/net/phy/Makefile b/drivers/net/phy/Makefile
index b7438b1b94b9..a6b50e7715d0 100644
--- a/drivers/net/phy/Makefile
+++ b/drivers/net/phy/Makefile
@@ -25,3 +25,4 @@ obj-$(CONFIG_MICREL_PHY)	+= micrel.o
 obj-$(CONFIG_MDIO_OCTEON)	+= mdio-octeon.o
 obj-$(CONFIG_MICREL_KS8995MA)	+= spi_ks8995.o
 obj-$(CONFIG_AMD_PHY)		+= amd.o
+obj-$(CONFIG_MDIO_BUS_MUX)	+= mdio-mux.o
diff --git a/drivers/net/phy/mdio-mux.c b/drivers/net/phy/mdio-mux.c
new file mode 100644
index 000000000000..39ea0674dcde
--- /dev/null
+++ b/drivers/net/phy/mdio-mux.c
@@ -0,0 +1,192 @@
+/*
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License.  See the file "COPYING" in the main directory of this archive
+ * for more details.
+ *
+ * Copyright (C) 2011, 2012 Cavium, Inc.
+ */
+
+#include <linux/platform_device.h>
+#include <linux/mdio-mux.h>
+#include <linux/of_mdio.h>
+#include <linux/device.h>
+#include <linux/module.h>
+#include <linux/phy.h>
+
+#define DRV_VERSION "1.0"
+#define DRV_DESCRIPTION "MDIO bus multiplexer driver"
+
+struct mdio_mux_child_bus;
+
+struct mdio_mux_parent_bus {
+	struct mii_bus *mii_bus;
+	int current_child;
+	int parent_id;
+	void *switch_data;
+	int (*switch_fn)(int current_child, int desired_child, void *data);
+
+	/* List of our children linked through their next fields. */
+	struct mdio_mux_child_bus *children;
+};
+
+struct mdio_mux_child_bus {
+	struct mii_bus *mii_bus;
+	struct mdio_mux_parent_bus *parent;
+	struct mdio_mux_child_bus *next;
+	int bus_number;
+	int phy_irq[PHY_MAX_ADDR];
+};
+
+/*
+ * The parent bus' lock is used to order access to the switch_fn.
+ */
+static int mdio_mux_read(struct mii_bus *bus, int phy_id, int regnum)
+{
+	struct mdio_mux_child_bus *cb = bus->priv;
+	struct mdio_mux_parent_bus *pb = cb->parent;
+	int r;
+
+	mutex_lock(&pb->mii_bus->mdio_lock);
+	r = pb->switch_fn(pb->current_child, cb->bus_number, pb->switch_data);
+	if (r)
+		goto out;
+
+	pb->current_child = cb->bus_number;
+
+	r = pb->mii_bus->read(pb->mii_bus, phy_id, regnum);
+out:
+	mutex_unlock(&pb->mii_bus->mdio_lock);
+
+	return r;
+}
+
+/*
+ * The parent bus' lock is used to order access to the switch_fn.
+ */
+static int mdio_mux_write(struct mii_bus *bus, int phy_id,
+			  int regnum, u16 val)
+{
+	struct mdio_mux_child_bus *cb = bus->priv;
+	struct mdio_mux_parent_bus *pb = cb->parent;
+
+	int r;
+
+	mutex_lock(&pb->mii_bus->mdio_lock);
+	r = pb->switch_fn(pb->current_child, cb->bus_number, pb->switch_data);
+	if (r)
+		goto out;
+
+	pb->current_child = cb->bus_number;
+
+	r = pb->mii_bus->write(pb->mii_bus, phy_id, regnum, val);
+out:
+	mutex_unlock(&pb->mii_bus->mdio_lock);
+
+	return r;
+}
+
+static int parent_count;
+
+int mdio_mux_init(struct device *dev,
+		  int (*switch_fn)(int cur, int desired, void *data),
+		  void **mux_handle,
+		  void *data)
+{
+	struct device_node *parent_bus_node;
+	struct device_node *child_bus_node;
+	int r, ret_val;
+	struct mii_bus *parent_bus;
+	struct mdio_mux_parent_bus *pb;
+	struct mdio_mux_child_bus *cb;
+
+	if (!dev->of_node)
+		return -ENODEV;
+
+	parent_bus_node = of_parse_phandle(dev->of_node, "mdio-parent-bus", 0);
+
+	if (!parent_bus_node)
+		return -ENODEV;
+
+	parent_bus = of_mdio_find_bus(parent_bus_node);
+	if (parent_bus == NULL) {
+		ret_val = -EPROBE_DEFER;
+		goto err_parent_bus;
+	}
+
+	pb = devm_kzalloc(dev, sizeof(*pb), GFP_KERNEL);
+	if (pb == NULL) {
+		ret_val = -ENOMEM;
+		goto err_parent_bus;
+	}
+
+	pb->switch_data = data;
+	pb->switch_fn = switch_fn;
+	pb->current_child = -1;
+	pb->parent_id = parent_count++;
+	pb->mii_bus = parent_bus;
+
+	ret_val = -ENODEV;
+	for_each_child_of_node(dev->of_node, child_bus_node) {
+		u32 v;
+
+		r = of_property_read_u32(child_bus_node, "reg", &v);
+		if (r)
+			continue;
+
+		cb = devm_kzalloc(dev, sizeof(*cb), GFP_KERNEL);
+		if (cb == NULL) {
+			dev_err(dev,
+				"Error: Failed to allocate memory for child\n");
+			ret_val = -ENOMEM;
+			break;
+		}
+		cb->bus_number = v;
+		cb->parent = pb;
+		cb->mii_bus = mdiobus_alloc();
+		cb->mii_bus->priv = cb;
+
+		cb->mii_bus->irq = cb->phy_irq;
+		cb->mii_bus->name = "mdio_mux";
+		snprintf(cb->mii_bus->id, MII_BUS_ID_SIZE, "%x.%x",
+			 pb->parent_id, v);
+		cb->mii_bus->parent = dev;
+		cb->mii_bus->read = mdio_mux_read;
+		cb->mii_bus->write = mdio_mux_write;
+		r = of_mdiobus_register(cb->mii_bus, child_bus_node);
+		if (r) {
+			mdiobus_free(cb->mii_bus);
+			devm_kfree(dev, cb);
+		} else {
+			of_node_get(child_bus_node);
+			cb->next = pb->children;
+			pb->children = cb;
+		}
+	}
+	if (pb->children) {
+		*mux_handle = pb;
+		dev_info(dev, "Version " DRV_VERSION "\n");
+		return 0;
+	}
+err_parent_bus:
+	of_node_put(parent_bus_node);
+	return ret_val;
+}
+EXPORT_SYMBOL_GPL(mdio_mux_init);
+
+void mdio_mux_uninit(void *mux_handle)
+{
+	struct mdio_mux_parent_bus *pb = mux_handle;
+	struct mdio_mux_child_bus *cb = pb->children;
+
+	while (cb) {
+		mdiobus_unregister(cb->mii_bus);
+		mdiobus_free(cb->mii_bus);
+		cb = cb->next;
+	}
+}
+EXPORT_SYMBOL_GPL(mdio_mux_uninit);
+
+MODULE_DESCRIPTION(DRV_DESCRIPTION);
+MODULE_VERSION(DRV_VERSION);
+MODULE_AUTHOR("David Daney");
+MODULE_LICENSE("GPL");