/*
 * 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;
};

/*
 * 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;

        /* In theory multiple mdio_mux could be stacked, thus creating
         * more than a single level of nesting.  But in practice,
         * SINGLE_DEPTH_NESTING will cover the vast majority of use
         * cases.  We use it, instead of trying to handle the general
         * case.
         */
        mutex_lock_nested(&pb->mii_bus->mdio_lock, SINGLE_DEPTH_NESTING);
        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_nested(&pb->mii_bus->mdio_lock, SINGLE_DEPTH_NESTING);
        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;

        pb = devm_kzalloc(dev, sizeof(*pb), GFP_KERNEL);
        if (pb == NULL) {
                ret_val = -ENOMEM;
                goto err_parent_bus;
        }

        parent_bus = of_mdio_find_bus(parent_bus_node);
        if (parent_bus == NULL) {
                ret_val = -EPROBE_DEFER;
                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_available_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;
                        of_node_put(child_bus_node);
                        break;
                }
                cb->bus_number = v;
                cb->parent = pb;

                cb->mii_bus = mdiobus_alloc();
                if (!cb->mii_bus) {
                        ret_val = -ENOMEM;
                        of_node_put(child_bus_node);
                        break;
                }
                cb->mii_bus->priv = cb;

                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;
        }

        /* balance the reference of_mdio_find_bus() took */
        put_device(&pb->mii_bus->dev);

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;
        }

        /* balance the reference of_mdio_find_bus() in mdio_mux_init() took */
        put_device(&pb->mii_bus->dev);
}
EXPORT_SYMBOL_GPL(mdio_mux_uninit);

MODULE_DESCRIPTION(DRV_DESCRIPTION);
MODULE_VERSION(DRV_VERSION);
MODULE_AUTHOR("David Daney");
MODULE_LICENSE("GPL");