// SPDX-License-Identifier: GPL-2.0-only
/*
 * I2C bus driver for Kontron COM modules
 *
 * Copyright (c) 2010-2013 Kontron Europe GmbH
 * Author: Michael Brunner <michael.brunner@kontron.com>
 *
 * The driver is based on the i2c-ocores driver by Peter Korsgaard.
 */

#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/i2c.h>
#include <linux/delay.h>
#include <linux/mfd/kempld.h>

#define KEMPLD_I2C_PRELOW       0x0b
#define KEMPLD_I2C_PREHIGH      0x0c
#define KEMPLD_I2C_DATA         0x0e

#define KEMPLD_I2C_CTRL         0x0d
#define I2C_CTRL_IEN            0x40
#define I2C_CTRL_EN             0x80

#define KEMPLD_I2C_STAT         0x0f
#define I2C_STAT_IF             0x01
#define I2C_STAT_TIP            0x02
#define I2C_STAT_ARBLOST        0x20
#define I2C_STAT_BUSY           0x40
#define I2C_STAT_NACK           0x80

#define KEMPLD_I2C_CMD          0x0f
#define I2C_CMD_START           0x91
#define I2C_CMD_STOP            0x41
#define I2C_CMD_READ            0x21
#define I2C_CMD_WRITE           0x11
#define I2C_CMD_READ_ACK        0x21
#define I2C_CMD_READ_NACK       0x29
#define I2C_CMD_IACK            0x01

#define KEMPLD_I2C_FREQ_MAX     2700    /* 2.7 mHz */
#define KEMPLD_I2C_FREQ_STD     100     /* 100 kHz */

enum {
        STATE_DONE = 0,
        STATE_INIT,
        STATE_ADDR,
        STATE_ADDR10,
        STATE_START,
        STATE_WRITE,
        STATE_READ,
        STATE_ERROR,
};

struct kempld_i2c_data {
        struct device                   *dev;
        struct kempld_device_data       *pld;
        struct i2c_adapter              adap;
        struct i2c_msg                  *msg;
        int                             pos;
        int                             nmsgs;
        int                             state;
        bool                            was_active;
};

static unsigned int bus_frequency = KEMPLD_I2C_FREQ_STD;
module_param(bus_frequency, uint, 0);
MODULE_PARM_DESC(bus_frequency, "Set I2C bus frequency in kHz (default="
                                __MODULE_STRING(KEMPLD_I2C_FREQ_STD)")");

static int i2c_bus = -1;
module_param(i2c_bus, int, 0);
MODULE_PARM_DESC(i2c_bus, "Set I2C bus number (default=-1 for dynamic assignment)");

static bool i2c_gpio_mux;
module_param(i2c_gpio_mux, bool, 0);
MODULE_PARM_DESC(i2c_gpio_mux, "Enable I2C port on GPIO out (default=false)");

/*
 * kempld_get_mutex must be called prior to calling this function.
 */
static int kempld_i2c_process(struct kempld_i2c_data *i2c)
{
        struct kempld_device_data *pld = i2c->pld;
        u8 stat = kempld_read8(pld, KEMPLD_I2C_STAT);
        struct i2c_msg *msg = i2c->msg;
        u8 addr;

        /* Ready? */
        if (stat & I2C_STAT_TIP)
                return -EBUSY;

        if (i2c->state == STATE_DONE || i2c->state == STATE_ERROR) {
                /* Stop has been sent */
                kempld_write8(pld, KEMPLD_I2C_CMD, I2C_CMD_IACK);
                if (i2c->state == STATE_ERROR)
                        return -EIO;
                return 0;
        }

        /* Error? */
        if (stat & I2C_STAT_ARBLOST) {
                i2c->state = STATE_ERROR;
                kempld_write8(pld, KEMPLD_I2C_CMD, I2C_CMD_STOP);
                return -EAGAIN;
        }

        if (i2c->state == STATE_INIT) {
                if (stat & I2C_STAT_BUSY)
                        return -EBUSY;

                i2c->state = STATE_ADDR;
        }

        if (i2c->state == STATE_ADDR) {
                /* 10 bit address? */
                if (i2c->msg->flags & I2C_M_TEN) {
                        addr = i2c_10bit_addr_hi_from_msg(msg);
                        i2c->state = STATE_ADDR10;
                } else {
                        addr = i2c_8bit_addr_from_msg(i2c->msg);
                        i2c->state = STATE_START;
                }

                kempld_write8(pld, KEMPLD_I2C_DATA, addr);
                kempld_write8(pld, KEMPLD_I2C_CMD, I2C_CMD_START);

                return 0;
        }

        /* Second part of 10 bit addressing */
        if (i2c->state == STATE_ADDR10) {
                addr = i2c_10bit_addr_lo_from_msg(msg);
                i2c->state = STATE_START;

                kempld_write8(pld, KEMPLD_I2C_DATA, addr);
                kempld_write8(pld, KEMPLD_I2C_CMD, I2C_CMD_WRITE);

                return 0;
        }

        if (i2c->state == STATE_START || i2c->state == STATE_WRITE) {
                i2c->state = (msg->flags & I2C_M_RD) ? STATE_READ : STATE_WRITE;

                if (stat & I2C_STAT_NACK) {
                        i2c->state = STATE_ERROR;
                        kempld_write8(pld, KEMPLD_I2C_CMD, I2C_CMD_STOP);
                        return -ENXIO;
                }
        } else {
                msg->buf[i2c->pos++] = kempld_read8(pld, KEMPLD_I2C_DATA);
        }

        if (i2c->pos >= msg->len) {
                i2c->nmsgs--;
                i2c->msg++;
                i2c->pos = 0;
                msg = i2c->msg;

                if (i2c->nmsgs) {
                        if (!(msg->flags & I2C_M_NOSTART)) {
                                i2c->state = STATE_ADDR;
                                return 0;
                        } else {
                                i2c->state = (msg->flags & I2C_M_RD)
                                        ? STATE_READ : STATE_WRITE;
                        }
                } else {
                        i2c->state = STATE_DONE;
                        kempld_write8(pld, KEMPLD_I2C_CMD, I2C_CMD_STOP);
                        return 0;
                }
        }

        if (i2c->state == STATE_READ) {
                kempld_write8(pld, KEMPLD_I2C_CMD, i2c->pos == (msg->len - 1) ?
                              I2C_CMD_READ_NACK : I2C_CMD_READ_ACK);
        } else {
                kempld_write8(pld, KEMPLD_I2C_DATA, msg->buf[i2c->pos++]);
                kempld_write8(pld, KEMPLD_I2C_CMD, I2C_CMD_WRITE);
        }

        return 0;
}

static int kempld_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
                                int num)
{
        struct kempld_i2c_data *i2c = i2c_get_adapdata(adap);
        struct kempld_device_data *pld = i2c->pld;
        unsigned long timeout = jiffies + HZ;
        int ret;

        i2c->msg = msgs;
        i2c->pos = 0;
        i2c->nmsgs = num;
        i2c->state = STATE_INIT;

        /* Handle the transfer */
        while (time_before(jiffies, timeout)) {
                kempld_get_mutex(pld);
                ret = kempld_i2c_process(i2c);
                kempld_release_mutex(pld);

                if (i2c->state == STATE_DONE || i2c->state == STATE_ERROR)
                        return (i2c->state == STATE_DONE) ? num : ret;

                if (ret == 0)
                        timeout = jiffies + HZ;

                usleep_range(5, 15);
        }

        i2c->state = STATE_ERROR;

        return -ETIMEDOUT;
}

/*
 * kempld_get_mutex must be called prior to calling this function.
 */
static void kempld_i2c_device_init(struct kempld_i2c_data *i2c)
{
        struct kempld_device_data *pld = i2c->pld;
        u16 prescale_corr;
        long prescale;
        u8 ctrl;
        u8 stat;
        u8 cfg;

        /* Make sure the device is disabled */
        ctrl = kempld_read8(pld, KEMPLD_I2C_CTRL);
        ctrl &= ~(I2C_CTRL_EN | I2C_CTRL_IEN);
        kempld_write8(pld, KEMPLD_I2C_CTRL, ctrl);

        if (bus_frequency > KEMPLD_I2C_FREQ_MAX)
                bus_frequency = KEMPLD_I2C_FREQ_MAX;

        if (pld->info.spec_major == 1)
                prescale = pld->pld_clock / (bus_frequency * 5) - 1000;
        else
                prescale = pld->pld_clock / (bus_frequency * 4) - 3000;

        if (prescale < 0)
                prescale = 0;

        /* Round to the best matching value */
        prescale_corr = prescale / 1000;
        if (prescale % 1000 >= 500)
                prescale_corr++;

        kempld_write8(pld, KEMPLD_I2C_PRELOW, prescale_corr & 0xff);
        kempld_write8(pld, KEMPLD_I2C_PREHIGH, prescale_corr >> 8);

        /* Activate I2C bus output on GPIO pins */
        cfg = kempld_read8(pld, KEMPLD_CFG);
        if (i2c_gpio_mux)
                cfg |= KEMPLD_CFG_GPIO_I2C_MUX;
        else
                cfg &= ~KEMPLD_CFG_GPIO_I2C_MUX;
        kempld_write8(pld, KEMPLD_CFG, cfg);

        /* Enable the device */
        kempld_write8(pld, KEMPLD_I2C_CMD, I2C_CMD_IACK);
        ctrl |= I2C_CTRL_EN;
        kempld_write8(pld, KEMPLD_I2C_CTRL, ctrl);

        stat = kempld_read8(pld, KEMPLD_I2C_STAT);
        if (stat & I2C_STAT_BUSY)
                kempld_write8(pld, KEMPLD_I2C_CMD, I2C_CMD_STOP);
}

static u32 kempld_i2c_func(struct i2c_adapter *adap)
{
        return I2C_FUNC_I2C | I2C_FUNC_10BIT_ADDR | I2C_FUNC_SMBUS_EMUL;
}

static const struct i2c_algorithm kempld_i2c_algorithm = {
        .xfer = kempld_i2c_xfer,
        .functionality = kempld_i2c_func,
};

static const struct i2c_adapter kempld_i2c_adapter = {
        .owner          = THIS_MODULE,
        .name           = "i2c-kempld",
        .class          = I2C_CLASS_HWMON | I2C_CLASS_DEPRECATED,
        .algo           = &kempld_i2c_algorithm,
};

static int kempld_i2c_probe(struct platform_device *pdev)
{
        struct kempld_device_data *pld = dev_get_drvdata(pdev->dev.parent);
        struct kempld_i2c_data *i2c;
        int ret;
        u8 ctrl;

        i2c = devm_kzalloc(&pdev->dev, sizeof(*i2c), GFP_KERNEL);
        if (!i2c)
                return -ENOMEM;

        i2c->pld = pld;
        i2c->dev = &pdev->dev;
        i2c->adap = kempld_i2c_adapter;
        i2c->adap.dev.parent = i2c->dev;
        ACPI_COMPANION_SET(&i2c->adap.dev, ACPI_COMPANION(&pdev->dev));
        i2c_set_adapdata(&i2c->adap, i2c);
        platform_set_drvdata(pdev, i2c);

        kempld_get_mutex(pld);
        ctrl = kempld_read8(pld, KEMPLD_I2C_CTRL);

        if (ctrl & I2C_CTRL_EN)
                i2c->was_active = true;

        kempld_i2c_device_init(i2c);
        kempld_release_mutex(pld);

        /* Add I2C adapter to I2C tree */
        if (i2c_bus >= -1)
                i2c->adap.nr = i2c_bus;
        ret = i2c_add_numbered_adapter(&i2c->adap);
        if (ret)
                return ret;

        dev_info(i2c->dev, "I2C bus initialized at %dkHz\n",
                 bus_frequency);

        return 0;
}

static void kempld_i2c_remove(struct platform_device *pdev)
{
        struct kempld_i2c_data *i2c = platform_get_drvdata(pdev);
        struct kempld_device_data *pld = i2c->pld;
        u8 ctrl;

        kempld_get_mutex(pld);
        /*
         * Disable I2C logic if it was not activated before the
         * driver loaded
         */
        if (!i2c->was_active) {
                ctrl = kempld_read8(pld, KEMPLD_I2C_CTRL);
                ctrl &= ~I2C_CTRL_EN;
                kempld_write8(pld, KEMPLD_I2C_CTRL, ctrl);
        }
        kempld_release_mutex(pld);

        i2c_del_adapter(&i2c->adap);
}

static int kempld_i2c_suspend(struct device *dev)
{
        struct kempld_i2c_data *i2c = dev_get_drvdata(dev);
        struct kempld_device_data *pld = i2c->pld;
        u8 ctrl;

        kempld_get_mutex(pld);
        ctrl = kempld_read8(pld, KEMPLD_I2C_CTRL);
        ctrl &= ~I2C_CTRL_EN;
        kempld_write8(pld, KEMPLD_I2C_CTRL, ctrl);
        kempld_release_mutex(pld);

        return 0;
}

static int kempld_i2c_resume(struct device *dev)
{
        struct kempld_i2c_data *i2c = dev_get_drvdata(dev);
        struct kempld_device_data *pld = i2c->pld;

        kempld_get_mutex(pld);
        kempld_i2c_device_init(i2c);
        kempld_release_mutex(pld);

        return 0;
}

static DEFINE_SIMPLE_DEV_PM_OPS(kempld_i2c_pm_ops,
                                kempld_i2c_suspend, kempld_i2c_resume);

static struct platform_driver kempld_i2c_driver = {
        .driver = {
                .name = "kempld-i2c",
                .pm = pm_sleep_ptr(&kempld_i2c_pm_ops),
        },
        .probe          = kempld_i2c_probe,
        .remove         = kempld_i2c_remove,
};

module_platform_driver(kempld_i2c_driver);

MODULE_DESCRIPTION("KEM PLD I2C Driver");
MODULE_AUTHOR("Michael Brunner <michael.brunner@kontron.com>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:kempld_i2c");