/**
 * i2c-exynos5.c - Samsung Exynos5 I2C Controller Driver
 *
 * Copyright (C) 2013 Samsung Electronics Co., Ltd.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
*/

#include <linux/kernel.h>
#include <linux/module.h>

#include <linux/i2c.h>
#include <linux/time.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/platform_device.h>
#include <linux/clk.h>
#include <linux/slab.h>
#include <linux/io.h>
#include <linux/of_address.h>
#include <linux/of_device.h>
#include <linux/of_irq.h>
#include <linux/spinlock.h>

/*
 * HSI2C controller from Samsung supports 2 modes of operation
 * 1. Auto mode: Where in master automatically controls the whole transaction
 * 2. Manual mode: Software controls the transaction by issuing commands
 *    START, READ, WRITE, STOP, RESTART in I2C_MANUAL_CMD register.
 *
 * Operation mode can be selected by setting AUTO_MODE bit in I2C_CONF register
 *
 * Special bits are available for both modes of operation to set commands
 * and for checking transfer status
 */

/* Register Map */
#define HSI2C_CTL               0x00
#define HSI2C_FIFO_CTL          0x04
#define HSI2C_TRAILIG_CTL       0x08
#define HSI2C_CLK_CTL           0x0C
#define HSI2C_CLK_SLOT          0x10
#define HSI2C_INT_ENABLE        0x20
#define HSI2C_INT_STATUS        0x24
#define HSI2C_ERR_STATUS        0x2C
#define HSI2C_FIFO_STATUS       0x30
#define HSI2C_TX_DATA           0x34
#define HSI2C_RX_DATA           0x38
#define HSI2C_CONF              0x40
#define HSI2C_AUTO_CONF         0x44
#define HSI2C_TIMEOUT           0x48
#define HSI2C_MANUAL_CMD        0x4C
#define HSI2C_TRANS_STATUS      0x50
#define HSI2C_TIMING_HS1        0x54
#define HSI2C_TIMING_HS2        0x58
#define HSI2C_TIMING_HS3        0x5C
#define HSI2C_TIMING_FS1        0x60
#define HSI2C_TIMING_FS2        0x64
#define HSI2C_TIMING_FS3        0x68
#define HSI2C_TIMING_SLA        0x6C
#define HSI2C_ADDR              0x70

/* I2C_CTL Register bits */
#define HSI2C_FUNC_MODE_I2C                     (1u << 0)
#define HSI2C_MASTER                            (1u << 3)
#define HSI2C_RXCHON                            (1u << 6)
#define HSI2C_TXCHON                            (1u << 7)
#define HSI2C_SW_RST                            (1u << 31)

/* I2C_FIFO_CTL Register bits */
#define HSI2C_RXFIFO_EN                         (1u << 0)
#define HSI2C_TXFIFO_EN                         (1u << 1)
#define HSI2C_RXFIFO_TRIGGER_LEVEL(x)           ((x) << 4)
#define HSI2C_TXFIFO_TRIGGER_LEVEL(x)           ((x) << 16)

/* I2C_TRAILING_CTL Register bits */
#define HSI2C_TRAILING_COUNT                    (0xf)

/* I2C_INT_EN Register bits */
#define HSI2C_INT_TX_ALMOSTEMPTY_EN             (1u << 0)
#define HSI2C_INT_RX_ALMOSTFULL_EN              (1u << 1)
#define HSI2C_INT_TRAILING_EN                   (1u << 6)

/* I2C_INT_STAT Register bits */
#define HSI2C_INT_TX_ALMOSTEMPTY                (1u << 0)
#define HSI2C_INT_RX_ALMOSTFULL                 (1u << 1)
#define HSI2C_INT_TX_UNDERRUN                   (1u << 2)
#define HSI2C_INT_TX_OVERRUN                    (1u << 3)
#define HSI2C_INT_RX_UNDERRUN                   (1u << 4)
#define HSI2C_INT_RX_OVERRUN                    (1u << 5)
#define HSI2C_INT_TRAILING                      (1u << 6)
#define HSI2C_INT_I2C                           (1u << 9)

#define HSI2C_INT_TRANS_DONE                    (1u << 7)
#define HSI2C_INT_TRANS_ABORT                   (1u << 8)
#define HSI2C_INT_NO_DEV_ACK                    (1u << 9)
#define HSI2C_INT_NO_DEV                        (1u << 10)
#define HSI2C_INT_TIMEOUT                       (1u << 11)
#define HSI2C_INT_I2C_TRANS                     (HSI2C_INT_TRANS_DONE | \
                                                HSI2C_INT_TRANS_ABORT | \
                                                HSI2C_INT_NO_DEV_ACK |  \
                                                HSI2C_INT_NO_DEV |      \
                                                HSI2C_INT_TIMEOUT)

/* I2C_FIFO_STAT Register bits */
#define HSI2C_RX_FIFO_EMPTY                     (1u << 24)
#define HSI2C_RX_FIFO_FULL                      (1u << 23)
#define HSI2C_RX_FIFO_LVL(x)                    ((x >> 16) & 0x7f)
#define HSI2C_TX_FIFO_EMPTY                     (1u << 8)
#define HSI2C_TX_FIFO_FULL                      (1u << 7)
#define HSI2C_TX_FIFO_LVL(x)                    ((x >> 0) & 0x7f)

/* I2C_CONF Register bits */
#define HSI2C_AUTO_MODE                         (1u << 31)
#define HSI2C_10BIT_ADDR_MODE                   (1u << 30)
#define HSI2C_HS_MODE                           (1u << 29)

/* I2C_AUTO_CONF Register bits */
#define HSI2C_READ_WRITE                        (1u << 16)
#define HSI2C_STOP_AFTER_TRANS                  (1u << 17)
#define HSI2C_MASTER_RUN                        (1u << 31)

/* I2C_TIMEOUT Register bits */
#define HSI2C_TIMEOUT_EN                        (1u << 31)
#define HSI2C_TIMEOUT_MASK                      0xff

/* I2C_MANUAL_CMD register bits */
#define HSI2C_CMD_READ_DATA                     (1u << 4)
#define HSI2C_CMD_SEND_STOP                     (1u << 2)

/* I2C_TRANS_STATUS register bits */
#define HSI2C_MASTER_BUSY                       (1u << 17)
#define HSI2C_SLAVE_BUSY                        (1u << 16)

/* I2C_TRANS_STATUS register bits for Exynos5 variant */
#define HSI2C_TIMEOUT_AUTO                      (1u << 4)
#define HSI2C_NO_DEV                            (1u << 3)
#define HSI2C_NO_DEV_ACK                        (1u << 2)
#define HSI2C_TRANS_ABORT                       (1u << 1)
#define HSI2C_TRANS_DONE                        (1u << 0)

/* I2C_TRANS_STATUS register bits for Exynos7 variant */
#define HSI2C_MASTER_ST_MASK                    0xf
#define HSI2C_MASTER_ST_IDLE                    0x0
#define HSI2C_MASTER_ST_START                   0x1
#define HSI2C_MASTER_ST_RESTART                 0x2
#define HSI2C_MASTER_ST_STOP                    0x3
#define HSI2C_MASTER_ST_MASTER_ID               0x4
#define HSI2C_MASTER_ST_ADDR0                   0x5
#define HSI2C_MASTER_ST_ADDR1                   0x6
#define HSI2C_MASTER_ST_ADDR2                   0x7
#define HSI2C_MASTER_ST_ADDR_SR                 0x8
#define HSI2C_MASTER_ST_READ                    0x9
#define HSI2C_MASTER_ST_WRITE                   0xa
#define HSI2C_MASTER_ST_NO_ACK                  0xb
#define HSI2C_MASTER_ST_LOSE                    0xc
#define HSI2C_MASTER_ST_WAIT                    0xd
#define HSI2C_MASTER_ST_WAIT_CMD                0xe

/* I2C_ADDR register bits */
#define HSI2C_SLV_ADDR_SLV(x)                   ((x & 0x3ff) << 0)
#define HSI2C_SLV_ADDR_MAS(x)                   ((x & 0x3ff) << 10)
#define HSI2C_MASTER_ID(x)                      ((x & 0xff) << 24)
#define MASTER_ID(x)                            ((x & 0x7) + 0x08)

/*
 * Controller operating frequency, timing values for operation
 * are calculated against this frequency
 */
#define HSI2C_HS_TX_CLOCK       1000000
#define HSI2C_FS_TX_CLOCK       100000

#define EXYNOS5_I2C_TIMEOUT (msecs_to_jiffies(100))

enum i2c_type_exynos {
        I2C_TYPE_EXYNOS5,
        I2C_TYPE_EXYNOS7,
};

struct exynos5_i2c {
        struct i2c_adapter      adap;
        unsigned int            suspended:1;

        struct i2c_msg          *msg;
        struct completion       msg_complete;
        unsigned int            msg_ptr;

        unsigned int            irq;

        void __iomem            *regs;
        struct clk              *clk;
        struct device           *dev;
        int                     state;

        spinlock_t              lock;           /* IRQ synchronization */

        /*
         * Since the TRANS_DONE bit is cleared on read, and we may read it
         * either during an IRQ or after a transaction, keep track of its
         * state here.
         */
        int                     trans_done;

        /* Controller operating frequency */
        unsigned int            op_clock;

        /* Version of HS-I2C Hardware */
        const struct exynos_hsi2c_variant *variant;
};

/**
 * struct exynos_hsi2c_variant - platform specific HSI2C driver data
 * @fifo_depth: the fifo depth supported by the HSI2C module
 * @hw: the hardware variant of Exynos I2C controller
 *
 * Specifies platform specific configuration of HSI2C module.
 * Note: A structure for driver specific platform data is used for future
 * expansion of its usage.
 */
struct exynos_hsi2c_variant {
        unsigned int            fifo_depth;
        enum i2c_type_exynos    hw;
};

static const struct exynos_hsi2c_variant exynos5250_hsi2c_data = {
        .fifo_depth     = 64,
        .hw             = I2C_TYPE_EXYNOS5,
};

static const struct exynos_hsi2c_variant exynos5260_hsi2c_data = {
        .fifo_depth     = 16,
        .hw             = I2C_TYPE_EXYNOS5,
};

static const struct exynos_hsi2c_variant exynos7_hsi2c_data = {
        .fifo_depth     = 16,
        .hw             = I2C_TYPE_EXYNOS7,
};

static const struct of_device_id exynos5_i2c_match[] = {
        {
                .compatible = "samsung,exynos5-hsi2c",
                .data = &exynos5250_hsi2c_data
        }, {
                .compatible = "samsung,exynos5250-hsi2c",
                .data = &exynos5250_hsi2c_data
        }, {
                .compatible = "samsung,exynos5260-hsi2c",
                .data = &exynos5260_hsi2c_data
        }, {
                .compatible = "samsung,exynos7-hsi2c",
                .data = &exynos7_hsi2c_data
        }, {},
};
MODULE_DEVICE_TABLE(of, exynos5_i2c_match);

static void exynos5_i2c_clr_pend_irq(struct exynos5_i2c *i2c)
{
        writel(readl(i2c->regs + HSI2C_INT_STATUS),
                                i2c->regs + HSI2C_INT_STATUS);
}

/*
 * exynos5_i2c_set_timing: updates the registers with appropriate
 * timing values calculated
 *
 * Returns 0 on success, -EINVAL if the cycle length cannot
 * be calculated.
 */
static int exynos5_i2c_set_timing(struct exynos5_i2c *i2c, bool hs_timings)
{
        u32 i2c_timing_s1;
        u32 i2c_timing_s2;
        u32 i2c_timing_s3;
        u32 i2c_timing_sla;
        unsigned int t_start_su, t_start_hd;
        unsigned int t_stop_su;
        unsigned int t_data_su, t_data_hd;
        unsigned int t_scl_l, t_scl_h;
        unsigned int t_sr_release;
        unsigned int t_ftl_cycle;
        unsigned int clkin = clk_get_rate(i2c->clk);
        unsigned int op_clk = hs_timings ? i2c->op_clock :
                (i2c->op_clock >= HSI2C_HS_TX_CLOCK) ? HSI2C_FS_TX_CLOCK :
                i2c->op_clock;
        int div, clk_cycle, temp;

        /*
         * In case of HSI2C controller in Exynos5 series
         * FPCLK / FI2C =
         * (CLK_DIV + 1) * (TSCLK_L + TSCLK_H + 2) + 8 + 2 * FLT_CYCLE
         *
         * In case of HSI2C controllers in Exynos7 series
         * FPCLK / FI2C =
         * (CLK_DIV + 1) * (TSCLK_L + TSCLK_H + 2) + 8 + FLT_CYCLE
         *
         * clk_cycle := TSCLK_L + TSCLK_H
         * temp := (CLK_DIV + 1) * (clk_cycle + 2)
         *
         * Constraints: 4 <= temp, 0 <= CLK_DIV < 256, 2 <= clk_cycle <= 510
         *
         */
        t_ftl_cycle = (readl(i2c->regs + HSI2C_CONF) >> 16) & 0x7;
        temp = clkin / op_clk - 8 - t_ftl_cycle;
        if (i2c->variant->hw != I2C_TYPE_EXYNOS7)
                temp -= t_ftl_cycle;
        div = temp / 512;
        clk_cycle = temp / (div + 1) - 2;
        if (temp < 4 || div >= 256 || clk_cycle < 2) {
                dev_err(i2c->dev, "%s clock set-up failed\n",
                        hs_timings ? "HS" : "FS");
                return -EINVAL;
        }

        t_scl_l = clk_cycle / 2;
        t_scl_h = clk_cycle / 2;
        t_start_su = t_scl_l;
        t_start_hd = t_scl_l;
        t_stop_su = t_scl_l;
        t_data_su = t_scl_l / 2;
        t_data_hd = t_scl_l / 2;
        t_sr_release = clk_cycle;

        i2c_timing_s1 = t_start_su << 24 | t_start_hd << 16 | t_stop_su << 8;
        i2c_timing_s2 = t_data_su << 24 | t_scl_l << 8 | t_scl_h << 0;
        i2c_timing_s3 = div << 16 | t_sr_release << 0;
        i2c_timing_sla = t_data_hd << 0;

        dev_dbg(i2c->dev, "tSTART_SU: %X, tSTART_HD: %X, tSTOP_SU: %X\n",
                t_start_su, t_start_hd, t_stop_su);
        dev_dbg(i2c->dev, "tDATA_SU: %X, tSCL_L: %X, tSCL_H: %X\n",
                t_data_su, t_scl_l, t_scl_h);
        dev_dbg(i2c->dev, "nClkDiv: %X, tSR_RELEASE: %X\n",
                div, t_sr_release);
        dev_dbg(i2c->dev, "tDATA_HD: %X\n", t_data_hd);

        if (hs_timings) {
                writel(i2c_timing_s1, i2c->regs + HSI2C_TIMING_HS1);
                writel(i2c_timing_s2, i2c->regs + HSI2C_TIMING_HS2);
                writel(i2c_timing_s3, i2c->regs + HSI2C_TIMING_HS3);
        } else {
                writel(i2c_timing_s1, i2c->regs + HSI2C_TIMING_FS1);
                writel(i2c_timing_s2, i2c->regs + HSI2C_TIMING_FS2);
                writel(i2c_timing_s3, i2c->regs + HSI2C_TIMING_FS3);
        }
        writel(i2c_timing_sla, i2c->regs + HSI2C_TIMING_SLA);

        return 0;
}

static int exynos5_hsi2c_clock_setup(struct exynos5_i2c *i2c)
{
        /* always set Fast Speed timings */
        int ret = exynos5_i2c_set_timing(i2c, false);

        if (ret < 0 || i2c->op_clock < HSI2C_HS_TX_CLOCK)
                return ret;

        return exynos5_i2c_set_timing(i2c, true);
}

/*
 * exynos5_i2c_init: configures the controller for I2C functionality
 * Programs I2C controller for Master mode operation
 */
static void exynos5_i2c_init(struct exynos5_i2c *i2c)
{
        u32 i2c_conf = readl(i2c->regs + HSI2C_CONF);
        u32 i2c_timeout = readl(i2c->regs + HSI2C_TIMEOUT);

        /* Clear to disable Timeout */
        i2c_timeout &= ~HSI2C_TIMEOUT_EN;
        writel(i2c_timeout, i2c->regs + HSI2C_TIMEOUT);

        writel((HSI2C_FUNC_MODE_I2C | HSI2C_MASTER),
                                        i2c->regs + HSI2C_CTL);
        writel(HSI2C_TRAILING_COUNT, i2c->regs + HSI2C_TRAILIG_CTL);

        if (i2c->op_clock >= HSI2C_HS_TX_CLOCK) {
                writel(HSI2C_MASTER_ID(MASTER_ID(i2c->adap.nr)),
                                        i2c->regs + HSI2C_ADDR);
                i2c_conf |= HSI2C_HS_MODE;
        }

        writel(i2c_conf | HSI2C_AUTO_MODE, i2c->regs + HSI2C_CONF);
}

static void exynos5_i2c_reset(struct exynos5_i2c *i2c)
{
        u32 i2c_ctl;

        /* Set and clear the bit for reset */
        i2c_ctl = readl(i2c->regs + HSI2C_CTL);
        i2c_ctl |= HSI2C_SW_RST;
        writel(i2c_ctl, i2c->regs + HSI2C_CTL);

        i2c_ctl = readl(i2c->regs + HSI2C_CTL);
        i2c_ctl &= ~HSI2C_SW_RST;
        writel(i2c_ctl, i2c->regs + HSI2C_CTL);

        /* We don't expect calculations to fail during the run */
        exynos5_hsi2c_clock_setup(i2c);
        /* Initialize the configure registers */
        exynos5_i2c_init(i2c);
}

/*
 * exynos5_i2c_irq: top level IRQ servicing routine
 *
 * INT_STATUS registers gives the interrupt details. Further,
 * FIFO_STATUS or TRANS_STATUS registers are to be check for detailed
 * state of the bus.
 */
static irqreturn_t exynos5_i2c_irq(int irqno, void *dev_id)
{
        struct exynos5_i2c *i2c = dev_id;
        u32 fifo_level, int_status, fifo_status, trans_status;
        unsigned char byte;
        int len = 0;

        i2c->state = -EINVAL;

        spin_lock(&i2c->lock);

        int_status = readl(i2c->regs + HSI2C_INT_STATUS);
        writel(int_status, i2c->regs + HSI2C_INT_STATUS);

        /* handle interrupt related to the transfer status */
        if (i2c->variant->hw == I2C_TYPE_EXYNOS7) {
                if (int_status & HSI2C_INT_TRANS_DONE) {
                        i2c->trans_done = 1;
                        i2c->state = 0;
                } else if (int_status & HSI2C_INT_TRANS_ABORT) {
                        dev_dbg(i2c->dev, "Deal with arbitration lose\n");
                        i2c->state = -EAGAIN;
                        goto stop;
                } else if (int_status & HSI2C_INT_NO_DEV_ACK) {
                        dev_dbg(i2c->dev, "No ACK from device\n");
                        i2c->state = -ENXIO;
                        goto stop;
                } else if (int_status & HSI2C_INT_NO_DEV) {
                        dev_dbg(i2c->dev, "No device\n");
                        i2c->state = -ENXIO;
                        goto stop;
                } else if (int_status & HSI2C_INT_TIMEOUT) {
                        dev_dbg(i2c->dev, "Accessing device timed out\n");
                        i2c->state = -ETIMEDOUT;
                        goto stop;
                }
        } else if (int_status & HSI2C_INT_I2C) {
                trans_status = readl(i2c->regs + HSI2C_TRANS_STATUS);
                if (trans_status & HSI2C_NO_DEV_ACK) {
                        dev_dbg(i2c->dev, "No ACK from device\n");
                        i2c->state = -ENXIO;
                        goto stop;
                } else if (trans_status & HSI2C_NO_DEV) {
                        dev_dbg(i2c->dev, "No device\n");
                        i2c->state = -ENXIO;
                        goto stop;
                } else if (trans_status & HSI2C_TRANS_ABORT) {
                        dev_dbg(i2c->dev, "Deal with arbitration lose\n");
                        i2c->state = -EAGAIN;
                        goto stop;
                } else if (trans_status & HSI2C_TIMEOUT_AUTO) {
                        dev_dbg(i2c->dev, "Accessing device timed out\n");
                        i2c->state = -ETIMEDOUT;
                        goto stop;
                } else if (trans_status & HSI2C_TRANS_DONE) {
                        i2c->trans_done = 1;
                        i2c->state = 0;
                }
        }

        if ((i2c->msg->flags & I2C_M_RD) && (int_status &
                        (HSI2C_INT_TRAILING | HSI2C_INT_RX_ALMOSTFULL))) {
                fifo_status = readl(i2c->regs + HSI2C_FIFO_STATUS);
                fifo_level = HSI2C_RX_FIFO_LVL(fifo_status);
                len = min(fifo_level, i2c->msg->len - i2c->msg_ptr);

                while (len > 0) {
                        byte = (unsigned char)
                                readl(i2c->regs + HSI2C_RX_DATA);
                        i2c->msg->buf[i2c->msg_ptr++] = byte;
                        len--;
                }
                i2c->state = 0;
        } else if (int_status & HSI2C_INT_TX_ALMOSTEMPTY) {
                fifo_status = readl(i2c->regs + HSI2C_FIFO_STATUS);
                fifo_level = HSI2C_TX_FIFO_LVL(fifo_status);

                len = i2c->variant->fifo_depth - fifo_level;
                if (len > (i2c->msg->len - i2c->msg_ptr)) {
                        u32 int_en = readl(i2c->regs + HSI2C_INT_ENABLE);

                        int_en &= ~HSI2C_INT_TX_ALMOSTEMPTY_EN;
                        writel(int_en, i2c->regs + HSI2C_INT_ENABLE);
                        len = i2c->msg->len - i2c->msg_ptr;
                }

                while (len > 0) {
                        byte = i2c->msg->buf[i2c->msg_ptr++];
                        writel(byte, i2c->regs + HSI2C_TX_DATA);
                        len--;
                }
                i2c->state = 0;
        }

 stop:
        if ((i2c->trans_done && (i2c->msg->len == i2c->msg_ptr)) ||
            (i2c->state < 0)) {
                writel(0, i2c->regs + HSI2C_INT_ENABLE);
                exynos5_i2c_clr_pend_irq(i2c);
                complete(&i2c->msg_complete);
        }

        spin_unlock(&i2c->lock);

        return IRQ_HANDLED;
}

/*
 * exynos5_i2c_wait_bus_idle
 *
 * Wait for the bus to go idle, indicated by the MASTER_BUSY bit being
 * cleared.
 *
 * Returns -EBUSY if the bus cannot be bought to idle
 */
static int exynos5_i2c_wait_bus_idle(struct exynos5_i2c *i2c)
{
        unsigned long stop_time;
        u32 trans_status;

        /* wait for 100 milli seconds for the bus to be idle */
        stop_time = jiffies + msecs_to_jiffies(100) + 1;
        do {
                trans_status = readl(i2c->regs + HSI2C_TRANS_STATUS);
                if (!(trans_status & HSI2C_MASTER_BUSY))
                        return 0;

                usleep_range(50, 200);
        } while (time_before(jiffies, stop_time));

        return -EBUSY;
}

static void exynos5_i2c_bus_recover(struct exynos5_i2c *i2c)
{
        u32 val;

        val = readl(i2c->regs + HSI2C_CTL) | HSI2C_RXCHON;
        writel(val, i2c->regs + HSI2C_CTL);
        val = readl(i2c->regs + HSI2C_CONF) & ~HSI2C_AUTO_MODE;
        writel(val, i2c->regs + HSI2C_CONF);

        /*
         * Specification says master should send nine clock pulses. It can be
         * emulated by sending manual read command (nine pulses for read eight
         * bits + one pulse for NACK).
         */
        writel(HSI2C_CMD_READ_DATA, i2c->regs + HSI2C_MANUAL_CMD);
        exynos5_i2c_wait_bus_idle(i2c);
        writel(HSI2C_CMD_SEND_STOP, i2c->regs + HSI2C_MANUAL_CMD);
        exynos5_i2c_wait_bus_idle(i2c);

        val = readl(i2c->regs + HSI2C_CTL) & ~HSI2C_RXCHON;
        writel(val, i2c->regs + HSI2C_CTL);
        val = readl(i2c->regs + HSI2C_CONF) | HSI2C_AUTO_MODE;
        writel(val, i2c->regs + HSI2C_CONF);
}

static void exynos5_i2c_bus_check(struct exynos5_i2c *i2c)
{
        unsigned long timeout;

        if (i2c->variant->hw != I2C_TYPE_EXYNOS7)
                return;

        /*
         * HSI2C_MASTER_ST_LOSE state in EXYNOS7 variant before transaction
         * indicates that bus is stuck (SDA is low). In such case bus recovery
         * can be performed.
         */
        timeout = jiffies + msecs_to_jiffies(100);
        for (;;) {
                u32 st = readl(i2c->regs + HSI2C_TRANS_STATUS);

                if ((st & HSI2C_MASTER_ST_MASK) != HSI2C_MASTER_ST_LOSE)
                        return;

                if (time_is_before_jiffies(timeout))
                        return;

                exynos5_i2c_bus_recover(i2c);
        }
}

/*
 * exynos5_i2c_message_start: Configures the bus and starts the xfer
 * i2c: struct exynos5_i2c pointer for the current bus
 * stop: Enables stop after transfer if set. Set for last transfer of
 *       in the list of messages.
 *
 * Configures the bus for read/write function
 * Sets chip address to talk to, message length to be sent.
 * Enables appropriate interrupts and sends start xfer command.
 */
static void exynos5_i2c_message_start(struct exynos5_i2c *i2c, int stop)
{
        u32 i2c_ctl;
        u32 int_en = 0;
        u32 i2c_auto_conf = 0;
        u32 fifo_ctl;
        unsigned long flags;
        unsigned short trig_lvl;

        if (i2c->variant->hw == I2C_TYPE_EXYNOS7)
                int_en |= HSI2C_INT_I2C_TRANS;
        else
                int_en |= HSI2C_INT_I2C;

        i2c_ctl = readl(i2c->regs + HSI2C_CTL);
        i2c_ctl &= ~(HSI2C_TXCHON | HSI2C_RXCHON);
        fifo_ctl = HSI2C_RXFIFO_EN | HSI2C_TXFIFO_EN;

        if (i2c->msg->flags & I2C_M_RD) {
                i2c_ctl |= HSI2C_RXCHON;

                i2c_auto_conf |= HSI2C_READ_WRITE;

                trig_lvl = (i2c->msg->len > i2c->variant->fifo_depth) ?
                        (i2c->variant->fifo_depth * 3 / 4) : i2c->msg->len;
                fifo_ctl |= HSI2C_RXFIFO_TRIGGER_LEVEL(trig_lvl);

                int_en |= (HSI2C_INT_RX_ALMOSTFULL_EN |
                        HSI2C_INT_TRAILING_EN);
        } else {
                i2c_ctl |= HSI2C_TXCHON;

                trig_lvl = (i2c->msg->len > i2c->variant->fifo_depth) ?
                        (i2c->variant->fifo_depth * 1 / 4) : i2c->msg->len;
                fifo_ctl |= HSI2C_TXFIFO_TRIGGER_LEVEL(trig_lvl);

                int_en |= HSI2C_INT_TX_ALMOSTEMPTY_EN;
        }

        writel(HSI2C_SLV_ADDR_MAS(i2c->msg->addr), i2c->regs + HSI2C_ADDR);

        writel(fifo_ctl, i2c->regs + HSI2C_FIFO_CTL);
        writel(i2c_ctl, i2c->regs + HSI2C_CTL);

        exynos5_i2c_bus_check(i2c);

        /*
         * Enable interrupts before starting the transfer so that we don't
         * miss any INT_I2C interrupts.
         */
        spin_lock_irqsave(&i2c->lock, flags);
        writel(int_en, i2c->regs + HSI2C_INT_ENABLE);

        if (stop == 1)
                i2c_auto_conf |= HSI2C_STOP_AFTER_TRANS;
        i2c_auto_conf |= i2c->msg->len;
        i2c_auto_conf |= HSI2C_MASTER_RUN;
        writel(i2c_auto_conf, i2c->regs + HSI2C_AUTO_CONF);
        spin_unlock_irqrestore(&i2c->lock, flags);
}

static int exynos5_i2c_xfer_msg(struct exynos5_i2c *i2c,
                              struct i2c_msg *msgs, int stop)
{
        unsigned long timeout;
        int ret;

        i2c->msg = msgs;
        i2c->msg_ptr = 0;
        i2c->trans_done = 0;

        reinit_completion(&i2c->msg_complete);

        exynos5_i2c_message_start(i2c, stop);

        timeout = wait_for_completion_timeout(&i2c->msg_complete,
                                              EXYNOS5_I2C_TIMEOUT);
        if (timeout == 0)
                ret = -ETIMEDOUT;
        else
                ret = i2c->state;

        /*
         * If this is the last message to be transfered (stop == 1)
         * Then check if the bus can be brought back to idle.
         */
        if (ret == 0 && stop)
                ret = exynos5_i2c_wait_bus_idle(i2c);

        if (ret < 0) {
                exynos5_i2c_reset(i2c);
                if (ret == -ETIMEDOUT)
                        dev_warn(i2c->dev, "%s timeout\n",
                                 (msgs->flags & I2C_M_RD) ? "rx" : "tx");
        }

        /* Return the state as in interrupt routine */
        return ret;
}

static int exynos5_i2c_xfer(struct i2c_adapter *adap,
                        struct i2c_msg *msgs, int num)
{
        struct exynos5_i2c *i2c = adap->algo_data;
        int i, ret;

        if (i2c->suspended) {
                dev_err(i2c->dev, "HS-I2C is not initialized.\n");
                return -EIO;
        }

        ret = clk_enable(i2c->clk);
        if (ret)
                return ret;

        for (i = 0; i < num; ++i) {
                ret = exynos5_i2c_xfer_msg(i2c, msgs + i, i + 1 == num);
                if (ret)
                        break;
        }

        clk_disable(i2c->clk);

        return ret ?: num;
}

static u32 exynos5_i2c_func(struct i2c_adapter *adap)
{
        return I2C_FUNC_I2C | (I2C_FUNC_SMBUS_EMUL & ~I2C_FUNC_SMBUS_QUICK);
}

static const struct i2c_algorithm exynos5_i2c_algorithm = {
        .master_xfer            = exynos5_i2c_xfer,
        .functionality          = exynos5_i2c_func,
};

static int exynos5_i2c_probe(struct platform_device *pdev)
{
        struct device_node *np = pdev->dev.of_node;
        struct exynos5_i2c *i2c;
        struct resource *mem;
        int ret;

        i2c = devm_kzalloc(&pdev->dev, sizeof(struct exynos5_i2c), GFP_KERNEL);
        if (!i2c)
                return -ENOMEM;

        if (of_property_read_u32(np, "clock-frequency", &i2c->op_clock))
                i2c->op_clock = HSI2C_FS_TX_CLOCK;

        strlcpy(i2c->adap.name, "exynos5-i2c", sizeof(i2c->adap.name));
        i2c->adap.owner   = THIS_MODULE;
        i2c->adap.algo    = &exynos5_i2c_algorithm;
        i2c->adap.retries = 3;

        i2c->dev = &pdev->dev;
        i2c->clk = devm_clk_get(&pdev->dev, "hsi2c");
        if (IS_ERR(i2c->clk)) {
                dev_err(&pdev->dev, "cannot get clock\n");
                return -ENOENT;
        }

        ret = clk_prepare_enable(i2c->clk);
        if (ret)
                return ret;

        mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        i2c->regs = devm_ioremap_resource(&pdev->dev, mem);
        if (IS_ERR(i2c->regs)) {
                ret = PTR_ERR(i2c->regs);
                goto err_clk;
        }

        i2c->adap.dev.of_node = np;
        i2c->adap.algo_data = i2c;
        i2c->adap.dev.parent = &pdev->dev;

        /* Clear pending interrupts from u-boot or misc causes */
        exynos5_i2c_clr_pend_irq(i2c);

        spin_lock_init(&i2c->lock);
        init_completion(&i2c->msg_complete);

        i2c->irq = ret = platform_get_irq(pdev, 0);
        if (ret <= 0) {
                dev_err(&pdev->dev, "cannot find HS-I2C IRQ\n");
                ret = -EINVAL;
                goto err_clk;
        }

        ret = devm_request_irq(&pdev->dev, i2c->irq, exynos5_i2c_irq,
                                IRQF_NO_SUSPEND | IRQF_ONESHOT,
                                dev_name(&pdev->dev), i2c);

        if (ret != 0) {
                dev_err(&pdev->dev, "cannot request HS-I2C IRQ %d\n", i2c->irq);
                goto err_clk;
        }

        i2c->variant = of_device_get_match_data(&pdev->dev);

        ret = exynos5_hsi2c_clock_setup(i2c);
        if (ret)
                goto err_clk;

        exynos5_i2c_reset(i2c);

        ret = i2c_add_adapter(&i2c->adap);
        if (ret < 0)
                goto err_clk;

        platform_set_drvdata(pdev, i2c);

        clk_disable(i2c->clk);

        return 0;

 err_clk:
        clk_disable_unprepare(i2c->clk);
        return ret;
}

static int exynos5_i2c_remove(struct platform_device *pdev)
{
        struct exynos5_i2c *i2c = platform_get_drvdata(pdev);

        i2c_del_adapter(&i2c->adap);

        clk_unprepare(i2c->clk);

        return 0;
}

#ifdef CONFIG_PM_SLEEP
static int exynos5_i2c_suspend_noirq(struct device *dev)
{
        struct exynos5_i2c *i2c = dev_get_drvdata(dev);

        i2c->suspended = 1;

        clk_unprepare(i2c->clk);

        return 0;
}

static int exynos5_i2c_resume_noirq(struct device *dev)
{
        struct exynos5_i2c *i2c = dev_get_drvdata(dev);
        int ret = 0;

        ret = clk_prepare_enable(i2c->clk);
        if (ret)
                return ret;

        ret = exynos5_hsi2c_clock_setup(i2c);
        if (ret) {
                clk_disable_unprepare(i2c->clk);
                return ret;
        }

        exynos5_i2c_init(i2c);
        clk_disable(i2c->clk);
        i2c->suspended = 0;

        return 0;
}
#endif

static const struct dev_pm_ops exynos5_i2c_dev_pm_ops = {
        SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(exynos5_i2c_suspend_noirq,
                                      exynos5_i2c_resume_noirq)
};

static struct platform_driver exynos5_i2c_driver = {
        .probe          = exynos5_i2c_probe,
        .remove         = exynos5_i2c_remove,
        .driver         = {
                .name   = "exynos5-hsi2c",
                .pm     = &exynos5_i2c_dev_pm_ops,
                .of_match_table = exynos5_i2c_match,
        },
};

module_platform_driver(exynos5_i2c_driver);

MODULE_DESCRIPTION("Exynos5 HS-I2C Bus driver");
MODULE_AUTHOR("Naveen Krishna Chatradhi, <ch.naveen@samsung.com>");
MODULE_AUTHOR("Taekgyun Ko, <taeggyun.ko@samsung.com>");
MODULE_LICENSE("GPL v2");