/*
 * Simple memory-mapped device MDIO MUX driver
 *
 * Author: Timur Tabi <timur@freescale.com>
 *
 * 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/phy.h>
#include <linux/mdio-mux.h>

struct mdio_mux_mmioreg_state {
        void *mux_handle;
        phys_addr_t phys;
        unsigned int iosize;
        unsigned int 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 __iomem *p = ioremap(s->phys, s->iosize);
                if (!p)
                        return -ENOMEM;

                switch (s->iosize) {
                case sizeof(uint8_t): {
                        uint8_t x, y;

                        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);
                        }

                        break;
                }
                case sizeof(uint16_t): {
                        uint16_t x, y;

                        x = ioread16(p);
                        y = (x & ~s->mask) | desired_child;
                        if (x != y) {
                                iowrite16((x & ~s->mask) | desired_child, p);
                                pr_debug("%s: %04x -> %04x\n", __func__, x, y);
                        }

                        break;
                }
                case sizeof(uint32_t): {
                        uint32_t x, y;

                        x = ioread32(p);
                        y = (x & ~s->mask) | desired_child;
                        if (x != y) {
                                iowrite32((x & ~s->mask) | desired_child, p);
                                pr_debug("%s: %08x -> %08x\n", __func__, x, y);
                        }

                        break;
                }
                }

                iounmap(p);
        }

        return 0;
}

static int 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 %pOF\n", np);

        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 %pOF\n",
                        np);
                return ret;
        }
        s->phys = res.start;

        s->iosize = resource_size(&res);
        if (s->iosize != sizeof(uint8_t) &&
            s->iosize != sizeof(uint16_t) &&
            s->iosize != sizeof(uint32_t)) {
                dev_err(&pdev->dev, "only 8/16/32-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) >= BIT(s->iosize * 8)) {
                dev_err(&pdev->dev, "only 8/16/32-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 %pOF is "
                                "missing a 'reg' property\n", np2);
                        of_node_put(np2);
                        return -ENODEV;
                }
                if (be32_to_cpup(iprop) & ~s->mask) {
                        dev_err(&pdev->dev, "mdio-mux child node %pOF has "
                                "a 'reg' value with unmasked bits\n",
                                np2);
                        of_node_put(np2);
                        return -ENODEV;
                }
        }

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

        pdev->dev.platform_data = s;

        return 0;
}

static int 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 const 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",
                .of_match_table = mdio_mux_mmioreg_match,
        },
        .probe          = mdio_mux_mmioreg_probe,
        .remove         = mdio_mux_mmioreg_remove,
};

module_platform_driver(mdio_mux_mmioreg_driver);

MODULE_AUTHOR("Timur Tabi <timur@freescale.com>");
MODULE_DESCRIPTION("Memory-mapped device MDIO MUX driver");
MODULE_LICENSE("GPL v2");