// SPDX-License-Identifier: GPL-2.0
/* MOXA ART Ethernet (RTL8201CP) MDIO interface driver
 *
 * Copyright (C) 2013 Jonas Jensen <jonas.jensen@gmail.com>
 */

#include <linux/delay.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/of_address.h>
#include <linux/of_mdio.h>
#include <linux/phy.h>
#include <linux/platform_device.h>

#define REG_PHY_CTRL            0
#define REG_PHY_WRITE_DATA      4

/* REG_PHY_CTRL */
#define MIIWR                   BIT(27) /* init write sequence (auto cleared)*/
#define MIIRD                   BIT(26)
#define REGAD_MASK              0x3e00000
#define PHYAD_MASK              0x1f0000
#define MIIRDATA_MASK           0xffff

/* REG_PHY_WRITE_DATA */
#define MIIWDATA_MASK           0xffff

struct moxart_mdio_data {
        void __iomem            *base;
};

static int moxart_mdio_read(struct mii_bus *bus, int mii_id, int regnum)
{
        struct moxart_mdio_data *data = bus->priv;
        u32 ctrl = 0;
        unsigned int count = 5;

        dev_dbg(&bus->dev, "%s\n", __func__);

        ctrl |= MIIRD | ((mii_id << 16) & PHYAD_MASK) |
                ((regnum << 21) & REGAD_MASK);

        writel(ctrl, data->base + REG_PHY_CTRL);

        do {
                ctrl = readl(data->base + REG_PHY_CTRL);

                if (!(ctrl & MIIRD))
                        return ctrl & MIIRDATA_MASK;

                mdelay(10);
                count--;
        } while (count > 0);

        dev_dbg(&bus->dev, "%s timed out\n", __func__);

        return -ETIMEDOUT;
}

static int moxart_mdio_write(struct mii_bus *bus, int mii_id,
                             int regnum, u16 value)
{
        struct moxart_mdio_data *data = bus->priv;
        u32 ctrl = 0;
        unsigned int count = 5;

        dev_dbg(&bus->dev, "%s\n", __func__);

        ctrl |= MIIWR | ((mii_id << 16) & PHYAD_MASK) |
                ((regnum << 21) & REGAD_MASK);

        value &= MIIWDATA_MASK;

        writel(value, data->base + REG_PHY_WRITE_DATA);
        writel(ctrl, data->base + REG_PHY_CTRL);

        do {
                ctrl = readl(data->base + REG_PHY_CTRL);

                if (!(ctrl & MIIWR))
                        return 0;

                mdelay(10);
                count--;
        } while (count > 0);

        dev_dbg(&bus->dev, "%s timed out\n", __func__);

        return -ETIMEDOUT;
}

static int moxart_mdio_reset(struct mii_bus *bus)
{
        int data, i;

        for (i = 0; i < PHY_MAX_ADDR; i++) {
                data = moxart_mdio_read(bus, i, MII_BMCR);
                if (data < 0)
                        continue;

                data |= BMCR_RESET;
                if (moxart_mdio_write(bus, i, MII_BMCR, data) < 0)
                        continue;
        }

        return 0;
}

static int moxart_mdio_probe(struct platform_device *pdev)
{
        struct device_node *np = pdev->dev.of_node;
        struct mii_bus *bus;
        struct moxart_mdio_data *data;
        int ret, i;

        bus = mdiobus_alloc_size(sizeof(*data));
        if (!bus)
                return -ENOMEM;

        bus->name = "MOXA ART Ethernet MII";
        bus->read = &moxart_mdio_read;
        bus->write = &moxart_mdio_write;
        bus->reset = &moxart_mdio_reset;
        snprintf(bus->id, MII_BUS_ID_SIZE, "%s-%d-mii", pdev->name, pdev->id);
        bus->parent = &pdev->dev;

        /* Setting PHY_MAC_INTERRUPT here even if it has no effect,
         * of_mdiobus_register() sets these PHY_POLL.
         * Ideally, the interrupt from MAC controller could be used to
         * detect link state changes, not polling, i.e. if there was
         * a way phy_driver could set PHY_HAS_INTERRUPT but have that
         * interrupt handled in ethernet drivercode.
         */
        for (i = 0; i < PHY_MAX_ADDR; i++)
                bus->irq[i] = PHY_MAC_INTERRUPT;

        data = bus->priv;
        data->base = devm_platform_ioremap_resource(pdev, 0);
        if (IS_ERR(data->base)) {
                ret = PTR_ERR(data->base);
                goto err_out_free_mdiobus;
        }

        ret = of_mdiobus_register(bus, np);
        if (ret < 0)
                goto err_out_free_mdiobus;

        platform_set_drvdata(pdev, bus);

        return 0;

err_out_free_mdiobus:
        mdiobus_free(bus);
        return ret;
}

static void moxart_mdio_remove(struct platform_device *pdev)
{
        struct mii_bus *bus = platform_get_drvdata(pdev);

        mdiobus_unregister(bus);
        mdiobus_free(bus);
}

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

static struct platform_driver moxart_mdio_driver = {
        .probe = moxart_mdio_probe,
        .remove = moxart_mdio_remove,
        .driver = {
                .name = "moxart-mdio",
                .of_match_table = moxart_mdio_dt_ids,
        },
};

module_platform_driver(moxart_mdio_driver);

MODULE_DESCRIPTION("MOXA ART MDIO interface driver");
MODULE_AUTHOR("Jonas Jensen <jonas.jensen@gmail.com>");
MODULE_LICENSE("GPL v2");