// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2006-2007 PA Semi, Inc
 *
 * Author: Olof Johansson, PA Semi
 *
 * Maintained by: Olof Johansson <olof@lixom.net>
 *
 * Based on drivers/net/fs_enet/mii-bitbang.c.
 */

#include <linux/io.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/errno.h>
#include <linux/ioport.h>
#include <linux/interrupt.h>
#include <linux/phy.h>
#include <linux/of_address.h>
#include <linux/of_mdio.h>
#include <linux/platform_device.h>

#define DELAY 1

static void __iomem *gpio_regs;

struct gpio_priv {
        int mdc_pin;
        int mdio_pin;
};

#define MDC_PIN(bus)    (((struct gpio_priv *)bus->priv)->mdc_pin)
#define MDIO_PIN(bus)   (((struct gpio_priv *)bus->priv)->mdio_pin)

static inline void mdio_lo(struct mii_bus *bus)
{
        out_le32(gpio_regs+0x10, 1 << MDIO_PIN(bus));
}

static inline void mdio_hi(struct mii_bus *bus)
{
        out_le32(gpio_regs, 1 << MDIO_PIN(bus));
}

static inline void mdc_lo(struct mii_bus *bus)
{
        out_le32(gpio_regs+0x10, 1 << MDC_PIN(bus));
}

static inline void mdc_hi(struct mii_bus *bus)
{
        out_le32(gpio_regs, 1 << MDC_PIN(bus));
}

static inline void mdio_active(struct mii_bus *bus)
{
        out_le32(gpio_regs+0x20, (1 << MDC_PIN(bus)) | (1 << MDIO_PIN(bus)));
}

static inline void mdio_tristate(struct mii_bus *bus)
{
        out_le32(gpio_regs+0x30, (1 << MDIO_PIN(bus)));
}

static inline int mdio_read(struct mii_bus *bus)
{
        return !!(in_le32(gpio_regs+0x40) & (1 << MDIO_PIN(bus)));
}

static void clock_out(struct mii_bus *bus, int bit)
{
        if (bit)
                mdio_hi(bus);
        else
                mdio_lo(bus);
        udelay(DELAY);
        mdc_hi(bus);
        udelay(DELAY);
        mdc_lo(bus);
}

/* Utility to send the preamble, address, and register (common to read and write). */
static void bitbang_pre(struct mii_bus *bus, int read, u8 addr, u8 reg)
{
        int i;

        /* CFE uses a really long preamble (40 bits). We'll do the same. */
        mdio_active(bus);
        for (i = 0; i < 40; i++) {
                clock_out(bus, 1);
        }

        /* send the start bit (01) and the read opcode (10) or write (10) */
        clock_out(bus, 0);
        clock_out(bus, 1);

        clock_out(bus, read);
        clock_out(bus, !read);

        /* send the PHY address */
        for (i = 0; i < 5; i++) {
                clock_out(bus, (addr & 0x10) != 0);
                addr <<= 1;
        }

        /* send the register address */
        for (i = 0; i < 5; i++) {
                clock_out(bus, (reg & 0x10) != 0);
                reg <<= 1;
        }
}

static int gpio_mdio_read(struct mii_bus *bus, int phy_id, int location)
{
        u16 rdreg;
        int ret, i;
        u8 addr = phy_id & 0xff;
        u8 reg = location & 0xff;

        bitbang_pre(bus, 1, addr, reg);

        /* tri-state our MDIO I/O pin so we can read */
        mdio_tristate(bus);
        udelay(DELAY);
        mdc_hi(bus);
        udelay(DELAY);
        mdc_lo(bus);

        /* read 16 bits of register data, MSB first */
        rdreg = 0;
        for (i = 0; i < 16; i++) {
                mdc_lo(bus);
                udelay(DELAY);
                mdc_hi(bus);
                udelay(DELAY);
                mdc_lo(bus);
                udelay(DELAY);
                rdreg <<= 1;
                rdreg |= mdio_read(bus);
        }

        mdc_hi(bus);
        udelay(DELAY);
        mdc_lo(bus);
        udelay(DELAY);

        ret = rdreg;

        return ret;
}

static int gpio_mdio_write(struct mii_bus *bus, int phy_id, int location, u16 val)
{
        int i;

        u8 addr = phy_id & 0xff;
        u8 reg = location & 0xff;
        u16 value = val & 0xffff;

        bitbang_pre(bus, 0, addr, reg);

        /* send the turnaround (10) */
        mdc_lo(bus);
        mdio_hi(bus);
        udelay(DELAY);
        mdc_hi(bus);
        udelay(DELAY);
        mdc_lo(bus);
        mdio_lo(bus);
        udelay(DELAY);
        mdc_hi(bus);
        udelay(DELAY);

        /* write 16 bits of register data, MSB first */
        for (i = 0; i < 16; i++) {
                mdc_lo(bus);
                if (value & 0x8000)
                        mdio_hi(bus);
                else
                        mdio_lo(bus);
                udelay(DELAY);
                mdc_hi(bus);
                udelay(DELAY);
                value <<= 1;
        }

        /*
         * Tri-state the MDIO line.
         */
        mdio_tristate(bus);
        mdc_lo(bus);
        udelay(DELAY);
        mdc_hi(bus);
        udelay(DELAY);
        return 0;
}

static int gpio_mdio_reset(struct mii_bus *bus)
{
        /*nothing here - dunno how to reset it*/
        return 0;
}


static int gpio_mdio_probe(struct platform_device *ofdev)
{
        struct device *dev = &ofdev->dev;
        struct device_node *np = ofdev->dev.of_node;
        struct mii_bus *new_bus;
        struct gpio_priv *priv;
        const unsigned int *prop;
        int err;

        err = -ENOMEM;
        priv = kzalloc_obj(struct gpio_priv);
        if (!priv)
                goto out;

        new_bus = mdiobus_alloc();

        if (!new_bus)
                goto out_free_priv;

        new_bus->name = "pasemi gpio mdio bus";
        new_bus->read = &gpio_mdio_read;
        new_bus->write = &gpio_mdio_write;
        new_bus->reset = &gpio_mdio_reset;

        prop = of_get_property(np, "reg", NULL);
        snprintf(new_bus->id, MII_BUS_ID_SIZE, "%x", *prop);
        new_bus->priv = priv;

        prop = of_get_property(np, "mdc-pin", NULL);
        priv->mdc_pin = *prop;

        prop = of_get_property(np, "mdio-pin", NULL);
        priv->mdio_pin = *prop;

        new_bus->parent = dev;
        dev_set_drvdata(dev, new_bus);

        err = of_mdiobus_register(new_bus, np);

        if (err != 0) {
                pr_err("%s: Cannot register as MDIO bus, err %d\n",
                                new_bus->name, err);
                goto out_free_irq;
        }

        return 0;

out_free_irq:
        kfree(new_bus);
out_free_priv:
        kfree(priv);
out:
        return err;
}


static void gpio_mdio_remove(struct platform_device *dev)
{
        struct mii_bus *bus = dev_get_drvdata(&dev->dev);

        mdiobus_unregister(bus);

        dev_set_drvdata(&dev->dev, NULL);

        kfree(bus->priv);
        bus->priv = NULL;
        mdiobus_free(bus);
}

static const struct of_device_id gpio_mdio_match[] =
{
        {
                .compatible      = "gpio-mdio",
        },
        {},
};
MODULE_DEVICE_TABLE(of, gpio_mdio_match);

static struct platform_driver gpio_mdio_driver =
{
        .probe          = gpio_mdio_probe,
        .remove         = gpio_mdio_remove,
        .driver = {
                .name = "gpio-mdio-bitbang",
                .of_match_table = gpio_mdio_match,
        },
};

static int __init gpio_mdio_init(void)
{
        struct device_node *np;

        np = of_find_compatible_node(NULL, NULL, "1682m-gpio");
        if (!np)
                np = of_find_compatible_node(NULL, NULL,
                                             "pasemi,pwrficient-gpio");
        if (!np)
                return -ENODEV;
        gpio_regs = of_iomap(np, 0);
        of_node_put(np);

        if (!gpio_regs)
                return -ENODEV;

        return platform_driver_register(&gpio_mdio_driver);
}
module_init(gpio_mdio_init);

static void __exit gpio_mdio_exit(void)
{
        platform_driver_unregister(&gpio_mdio_driver);
        if (gpio_regs)
                iounmap(gpio_regs);
}
module_exit(gpio_mdio_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Olof Johansson <olof@lixom.net>");
MODULE_DESCRIPTION("Driver for MDIO over GPIO on PA Semi PWRficient-based boards");