/*
 * Broadcom UniMAC MDIO bus controller driver
 *
 * Copyright (C) 2014, Broadcom Corporation
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 */

#include <linux/kernel.h>
#include <linux/phy.h>
#include <linux/platform_device.h>
#include <linux/sched.h>
#include <linux/module.h>
#include <linux/io.h>
#include <linux/delay.h>

#include <linux/of.h>
#include <linux/of_platform.h>
#include <linux/of_mdio.h>

#define MDIO_CMD                0x00
#define  MDIO_START_BUSY        (1 << 29)
#define  MDIO_READ_FAIL         (1 << 28)
#define  MDIO_RD                (2 << 26)
#define  MDIO_WR                (1 << 26)
#define  MDIO_PMD_SHIFT         21
#define  MDIO_PMD_MASK          0x1F
#define  MDIO_REG_SHIFT         16
#define  MDIO_REG_MASK          0x1F

#define MDIO_CFG                0x04
#define  MDIO_C22               (1 << 0)
#define  MDIO_C45               0
#define  MDIO_CLK_DIV_SHIFT     4
#define  MDIO_CLK_DIV_MASK      0x3F
#define  MDIO_SUPP_PREAMBLE     (1 << 12)

struct unimac_mdio_priv {
        struct mii_bus          *mii_bus;
        void __iomem            *base;
};

static inline void unimac_mdio_start(struct unimac_mdio_priv *priv)
{
        u32 reg;

        reg = __raw_readl(priv->base + MDIO_CMD);
        reg |= MDIO_START_BUSY;
        __raw_writel(reg, priv->base + MDIO_CMD);
}

static inline unsigned int unimac_mdio_busy(struct unimac_mdio_priv *priv)
{
        return __raw_readl(priv->base + MDIO_CMD) & MDIO_START_BUSY;
}

static int unimac_mdio_read(struct mii_bus *bus, int phy_id, int reg)
{
        struct unimac_mdio_priv *priv = bus->priv;
        unsigned int timeout = 1000;
        u32 cmd;

        /* Prepare the read operation */
        cmd = MDIO_RD | (phy_id << MDIO_PMD_SHIFT) | (reg << MDIO_REG_SHIFT);
        __raw_writel(cmd, priv->base + MDIO_CMD);

        /* Start MDIO transaction */
        unimac_mdio_start(priv);

        do {
                if (!unimac_mdio_busy(priv))
                        break;

                usleep_range(1000, 2000);
        } while (timeout--);

        if (!timeout)
                return -ETIMEDOUT;

        cmd = __raw_readl(priv->base + MDIO_CMD);

        /* Some broken devices are known not to release the line during
         * turn-around, e.g: Broadcom BCM53125 external switches, so check for
         * that condition here and ignore the MDIO controller read failure
         * indication.
         */
        if (!(bus->phy_ignore_ta_mask & 1 << phy_id) && (cmd & MDIO_READ_FAIL))
                return -EIO;

        return cmd & 0xffff;
}

static int unimac_mdio_write(struct mii_bus *bus, int phy_id,
                             int reg, u16 val)
{
        struct unimac_mdio_priv *priv = bus->priv;
        unsigned int timeout = 1000;
        u32 cmd;

        /* Prepare the write operation */
        cmd = MDIO_WR | (phy_id << MDIO_PMD_SHIFT) |
                (reg << MDIO_REG_SHIFT) | (0xffff & val);
        __raw_writel(cmd, priv->base + MDIO_CMD);

        unimac_mdio_start(priv);

        do {
                if (!unimac_mdio_busy(priv))
                        break;

                usleep_range(1000, 2000);
        } while (timeout--);

        if (!timeout)
                return -ETIMEDOUT;

        return 0;
}

/* Workaround for integrated BCM7xxx Gigabit PHYs which have a problem with
 * their internal MDIO management controller making them fail to successfully
 * be read from or written to for the first transaction.  We insert a dummy
 * BMSR read here to make sure that phy_get_device() and get_phy_id() can
 * correctly read the PHY MII_PHYSID1/2 registers and successfully register a
 * PHY device for this peripheral.
 *
 * Once the PHY driver is registered, we can workaround subsequent reads from
 * there (e.g: during system-wide power management).
 *
 * bus->reset is invoked before mdiobus_scan during mdiobus_register and is
 * therefore the right location to stick that workaround. Since we do not want
 * to read from non-existing PHYs, we either use bus->phy_mask or do a manual
 * Device Tree scan to limit the search area.
 */
static int unimac_mdio_reset(struct mii_bus *bus)
{
        struct device_node *np = bus->dev.of_node;
        struct device_node *child;
        u32 read_mask = 0;
        int addr;

        if (!np) {
                read_mask = ~bus->phy_mask;
        } else {
                for_each_available_child_of_node(np, child) {
                        addr = of_mdio_parse_addr(&bus->dev, child);
                        if (addr < 0)
                                continue;

                        read_mask |= 1 << addr;
                }
        }

        for (addr = 0; addr < PHY_MAX_ADDR; addr++) {
                if (read_mask & 1 << addr)
                        mdiobus_read(bus, addr, MII_BMSR);
        }

        return 0;
}

static int unimac_mdio_probe(struct platform_device *pdev)
{
        struct unimac_mdio_priv *priv;
        struct device_node *np;
        struct mii_bus *bus;
        struct resource *r;
        int ret;

        np = pdev->dev.of_node;

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

        r = platform_get_resource(pdev, IORESOURCE_MEM, 0);

        /* Just ioremap, as this MDIO block is usually integrated into an
         * Ethernet MAC controller register range
         */
        priv->base = devm_ioremap(&pdev->dev, r->start, resource_size(r));
        if (!priv->base) {
                dev_err(&pdev->dev, "failed to remap register\n");
                return -ENOMEM;
        }

        priv->mii_bus = mdiobus_alloc();
        if (!priv->mii_bus)
                return -ENOMEM;

        bus = priv->mii_bus;
        bus->priv = priv;
        bus->name = "unimac MII bus";
        bus->parent = &pdev->dev;
        bus->read = unimac_mdio_read;
        bus->write = unimac_mdio_write;
        bus->reset = unimac_mdio_reset;
        snprintf(bus->id, MII_BUS_ID_SIZE, "%s", pdev->name);

        ret = of_mdiobus_register(bus, np);
        if (ret) {
                dev_err(&pdev->dev, "MDIO bus registration failed\n");
                goto out_mdio_free;
        }

        platform_set_drvdata(pdev, priv);

        dev_info(&pdev->dev, "Broadcom UniMAC MDIO bus at 0x%p\n", priv->base);

        return 0;

out_mdio_free:
        mdiobus_free(bus);
        return ret;
}

static int unimac_mdio_remove(struct platform_device *pdev)
{
        struct unimac_mdio_priv *priv = platform_get_drvdata(pdev);

        mdiobus_unregister(priv->mii_bus);
        mdiobus_free(priv->mii_bus);

        return 0;
}

static const struct of_device_id unimac_mdio_ids[] = {
        { .compatible = "brcm,genet-mdio-v4", },
        { .compatible = "brcm,genet-mdio-v3", },
        { .compatible = "brcm,genet-mdio-v2", },
        { .compatible = "brcm,genet-mdio-v1", },
        { .compatible = "brcm,unimac-mdio", },
        { /* sentinel */ },
};
MODULE_DEVICE_TABLE(of, unimac_mdio_ids);

static struct platform_driver unimac_mdio_driver = {
        .driver = {
                .name = "unimac-mdio",
                .of_match_table = unimac_mdio_ids,
        },
        .probe  = unimac_mdio_probe,
        .remove = unimac_mdio_remove,
};
module_platform_driver(unimac_mdio_driver);

MODULE_AUTHOR("Broadcom Corporation");
MODULE_DESCRIPTION("Broadcom UniMAC MDIO bus controller");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:unimac-mdio");