mdio-mux-mmioreg.c

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/*
 * Simple memory-mapped device MDIO MUX driver
 *
 * Author: Timur Tabi <[email protected]>
 *
 * Copyright 2012 Freescale Semiconductor, Inc.
 *
 * This file is licensed under the terms of the GNU General Public License
 * version 2.  This program is licensed "as is" without any warranty of any
 * kind, whether express or implied.
 */

#include <linux/platform_device.h>
#include <linux/device.h>
#include <linux/of_address.h>
#include <linux/of_mdio.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/phy.h>
#include <linux/mdio-mux.h>

struct mdio_mux_mmioreg_state {
    void *mux_handle;
    phys_addr_t phys;
    uint8_t mask;
};

/*
 * MDIO multiplexing switch function
 *
 * This function is called by the mdio-mux layer when it thinks the mdio bus
 * multiplexer needs to switch.
 *
 * 'current_child' is the current value of the mux register (masked via
 * s->mask).
 *
 * 'desired_child' is the value of the 'reg' property of the target child MDIO
 * node.
 *
 * The first time this function is called, current_child == -1.
 *
 * If current_child == desired_child, then the mux is already set to the
 * correct bus.
 */
static int mdio_mux_mmioreg_switch_fn(int current_child, int desired_child,
                      void *data)
{
    struct mdio_mux_mmioreg_state *s = data;

    if (current_child ^ desired_child) {
        void *p = ioremap(s->phys, 1);
        uint8_t x, y;

        if (!p)
            return -ENOMEM;

        x = ioread8(p);
        y = (x & ~s->mask) | desired_child;
        if (x != y) {
            iowrite8((x & ~s->mask) | desired_child, p);
            pr_debug("%s: %02x -> %02x\n", __func__, x, y);
        }

        iounmap(p);
    }

    return 0;
}

static int __devinit mdio_mux_mmioreg_probe(struct platform_device *pdev)
{
    struct device_node *np2, *np = pdev->dev.of_node;
    struct mdio_mux_mmioreg_state *s;
    struct resource res;
    const __be32 *iprop;
    int len, ret;

    dev_dbg(&pdev->dev, "probing node %s\n", np->full_name);

    s = devm_kzalloc(&pdev->dev, sizeof(*s), GFP_KERNEL);
    if (!s)
        return -ENOMEM;

    ret = of_address_to_resource(np, 0, &res);
    if (ret) {
        dev_err(&pdev->dev, "could not obtain memory map for node %s\n",
            np->full_name);
        return ret;
    }
    s->phys = res.start;

    if (resource_size(&res) != sizeof(uint8_t)) {
        dev_err(&pdev->dev, "only 8-bit registers are supported\n");
        return -EINVAL;
    }

    iprop = of_get_property(np, "mux-mask", &len);
    if (!iprop || len != sizeof(uint32_t)) {
        dev_err(&pdev->dev, "missing or invalid mux-mask property\n");
        return -ENODEV;
    }
    if (be32_to_cpup(iprop) > 255) {
        dev_err(&pdev->dev, "only 8-bit registers are supported\n");
        return -EINVAL;
    }
    s->mask = be32_to_cpup(iprop);

    /*
     * Verify that the 'reg' property of each child MDIO bus does not
     * set any bits outside of the 'mask'.
     */
    for_each_available_child_of_node(np, np2) {
        iprop = of_get_property(np2, "reg", &len);
        if (!iprop || len != sizeof(uint32_t)) {
            dev_err(&pdev->dev, "mdio-mux child node %s is "
                "missing a 'reg' property\n", np2->full_name);
            return -ENODEV;
        }
        if (be32_to_cpup(iprop) & ~s->mask) {
            dev_err(&pdev->dev, "mdio-mux child node %s has "
                "a 'reg' value with unmasked bits\n",
                np2->full_name);
            return -ENODEV;
        }
    }

    ret = mdio_mux_init(&pdev->dev, mdio_mux_mmioreg_switch_fn,
                &s->mux_handle, s);
    if (ret) {
        dev_err(&pdev->dev, "failed to register mdio-mux bus %s\n",
            np->full_name);
        return ret;
    }

    pdev->dev.platform_data = s;

    return 0;
}

static int __devexit mdio_mux_mmioreg_remove(struct platform_device *pdev)
{
    struct mdio_mux_mmioreg_state *s = dev_get_platdata(&pdev->dev);

    mdio_mux_uninit(s->mux_handle);

    return 0;
}

static struct of_device_id mdio_mux_mmioreg_match[] = {
    {
        .compatible = "mdio-mux-mmioreg",
    },
    {},
};
MODULE_DEVICE_TABLE(of, mdio_mux_mmioreg_match);

static struct platform_driver mdio_mux_mmioreg_driver = {
    .driver = {
        .name       = "mdio-mux-mmioreg",
        .owner      = THIS_MODULE,
        .of_match_table = mdio_mux_mmioreg_match,
    },
    .probe      = mdio_mux_mmioreg_probe,
    .remove     = __devexit_p(mdio_mux_mmioreg_remove),
};

module_platform_driver(mdio_mux_mmioreg_driver);

MODULE_AUTHOR("Timur Tabi <[email protected]>");
MODULE_DESCRIPTION("Memory-mapped device MDIO MUX driver");
MODULE_LICENSE("GPL v2");