mdio-mux.c

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/*
 * 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;

    /* 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;

    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_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;
            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");