/*
 * Copyright (C) 2013 STMicroelectronics
 *
 * I2C master mode controller driver, used in STMicroelectronics devices.
 *
 * Author: Maxime Coquelin <maxime.coquelin@st.com>
 *
 * 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/clk.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/i2c.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/module.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/of.h>
#include <linux/pinctrl/consumer.h>
#include <linux/platform_device.h>

/* SSC registers */
#define SSC_BRG                         0x000
#define SSC_TBUF                        0x004
#define SSC_RBUF                        0x008
#define SSC_CTL                         0x00C
#define SSC_IEN                         0x010
#define SSC_STA                         0x014
#define SSC_I2C                         0x018
#define SSC_SLAD                        0x01C
#define SSC_REP_START_HOLD              0x020
#define SSC_START_HOLD                  0x024
#define SSC_REP_START_SETUP             0x028
#define SSC_DATA_SETUP                  0x02C
#define SSC_STOP_SETUP                  0x030
#define SSC_BUS_FREE                    0x034
#define SSC_TX_FSTAT                    0x038
#define SSC_RX_FSTAT                    0x03C
#define SSC_PRE_SCALER_BRG              0x040
#define SSC_CLR                         0x080
#define SSC_NOISE_SUPP_WIDTH            0x100
#define SSC_PRSCALER                    0x104
#define SSC_NOISE_SUPP_WIDTH_DATAOUT    0x108
#define SSC_PRSCALER_DATAOUT            0x10c

/* SSC Control */
#define SSC_CTL_DATA_WIDTH_9            0x8
#define SSC_CTL_DATA_WIDTH_MSK          0xf
#define SSC_CTL_BM                      0xf
#define SSC_CTL_HB                      BIT(4)
#define SSC_CTL_PH                      BIT(5)
#define SSC_CTL_PO                      BIT(6)
#define SSC_CTL_SR                      BIT(7)
#define SSC_CTL_MS                      BIT(8)
#define SSC_CTL_EN                      BIT(9)
#define SSC_CTL_LPB                     BIT(10)
#define SSC_CTL_EN_TX_FIFO              BIT(11)
#define SSC_CTL_EN_RX_FIFO              BIT(12)
#define SSC_CTL_EN_CLST_RX              BIT(13)

/* SSC Interrupt Enable */
#define SSC_IEN_RIEN                    BIT(0)
#define SSC_IEN_TIEN                    BIT(1)
#define SSC_IEN_TEEN                    BIT(2)
#define SSC_IEN_REEN                    BIT(3)
#define SSC_IEN_PEEN                    BIT(4)
#define SSC_IEN_AASEN                   BIT(6)
#define SSC_IEN_STOPEN                  BIT(7)
#define SSC_IEN_ARBLEN                  BIT(8)
#define SSC_IEN_NACKEN                  BIT(10)
#define SSC_IEN_REPSTRTEN               BIT(11)
#define SSC_IEN_TX_FIFO_HALF            BIT(12)
#define SSC_IEN_RX_FIFO_HALF_FULL       BIT(14)

/* SSC Status */
#define SSC_STA_RIR                     BIT(0)
#define SSC_STA_TIR                     BIT(1)
#define SSC_STA_TE                      BIT(2)
#define SSC_STA_RE                      BIT(3)
#define SSC_STA_PE                      BIT(4)
#define SSC_STA_CLST                    BIT(5)
#define SSC_STA_AAS                     BIT(6)
#define SSC_STA_STOP                    BIT(7)
#define SSC_STA_ARBL                    BIT(8)
#define SSC_STA_BUSY                    BIT(9)
#define SSC_STA_NACK                    BIT(10)
#define SSC_STA_REPSTRT                 BIT(11)
#define SSC_STA_TX_FIFO_HALF            BIT(12)
#define SSC_STA_TX_FIFO_FULL            BIT(13)
#define SSC_STA_RX_FIFO_HALF            BIT(14)

/* SSC I2C Control */
#define SSC_I2C_I2CM                    BIT(0)
#define SSC_I2C_STRTG                   BIT(1)
#define SSC_I2C_STOPG                   BIT(2)
#define SSC_I2C_ACKG                    BIT(3)
#define SSC_I2C_AD10                    BIT(4)
#define SSC_I2C_TXENB                   BIT(5)
#define SSC_I2C_REPSTRTG                BIT(11)
#define SSC_I2C_SLAVE_DISABLE           BIT(12)

/* SSC Tx FIFO Status */
#define SSC_TX_FSTAT_STATUS             0x07

/* SSC Rx FIFO Status */
#define SSC_RX_FSTAT_STATUS             0x07

/* SSC Clear bit operation */
#define SSC_CLR_SSCAAS                  BIT(6)
#define SSC_CLR_SSCSTOP                 BIT(7)
#define SSC_CLR_SSCARBL                 BIT(8)
#define SSC_CLR_NACK                    BIT(10)
#define SSC_CLR_REPSTRT                 BIT(11)

/* SSC Clock Prescaler */
#define SSC_PRSC_VALUE                  0x0f


#define SSC_TXFIFO_SIZE                 0x8
#define SSC_RXFIFO_SIZE                 0x8

enum st_i2c_mode {
        I2C_MODE_STANDARD,
        I2C_MODE_FAST,
        I2C_MODE_END,
};

/**
 * struct st_i2c_timings - per-Mode tuning parameters
 * @rate: I2C bus rate
 * @rep_start_hold: I2C repeated start hold time requirement
 * @rep_start_setup: I2C repeated start set up time requirement
 * @start_hold: I2C start hold time requirement
 * @data_setup_time: I2C data set up time requirement
 * @stop_setup_time: I2C stop set up time requirement
 * @bus_free_time: I2C bus free time requirement
 * @sda_pulse_min_limit: I2C SDA pulse mini width limit
 */
struct st_i2c_timings {
        u32 rate;
        u32 rep_start_hold;
        u32 rep_start_setup;
        u32 start_hold;
        u32 data_setup_time;
        u32 stop_setup_time;
        u32 bus_free_time;
        u32 sda_pulse_min_limit;
};

/**
 * struct st_i2c_client - client specific data
 * @addr: 8-bit slave addr, including r/w bit
 * @count: number of bytes to be transfered
 * @xfered: number of bytes already transferred
 * @buf: data buffer
 * @result: result of the transfer
 * @stop: last I2C msg to be sent, i.e. STOP to be generated
 */
struct st_i2c_client {
        u8      addr;
        u32     count;
        u32     xfered;
        u8      *buf;
        int     result;
        bool    stop;
};

/**
 * struct st_i2c_dev - private data of the controller
 * @adap: I2C adapter for this controller
 * @dev: device for this controller
 * @base: virtual memory area
 * @complete: completion of I2C message
 * @irq: interrupt line for th controller
 * @clk: hw ssc block clock
 * @mode: I2C mode of the controller. Standard or Fast only supported
 * @scl_min_width_us: SCL line minimum pulse width in us
 * @sda_min_width_us: SDA line minimum pulse width in us
 * @client: I2C transfert information
 * @busy: I2C transfer on-going
 */
struct st_i2c_dev {
        struct i2c_adapter      adap;
        struct device           *dev;
        void __iomem            *base;
        struct completion       complete;
        int                     irq;
        struct clk              *clk;
        int                     mode;
        u32                     scl_min_width_us;
        u32                     sda_min_width_us;
        struct st_i2c_client    client;
        bool                    busy;
};

static inline void st_i2c_set_bits(void __iomem *reg, u32 mask)
{
        writel_relaxed(readl_relaxed(reg) | mask, reg);
}

static inline void st_i2c_clr_bits(void __iomem *reg, u32 mask)
{
        writel_relaxed(readl_relaxed(reg) & ~mask, reg);
}

/*
 * From I2C Specifications v0.5.
 *
 * All the values below have +10% margin added to be
 * compatible with some out-of-spec devices,
 * like HDMI link of the Toshiba 19AV600 TV.
 */
static struct st_i2c_timings i2c_timings[] = {
        [I2C_MODE_STANDARD] = {
                .rate                   = 100000,
                .rep_start_hold         = 4400,
                .rep_start_setup        = 5170,
                .start_hold             = 4400,
                .data_setup_time        = 275,
                .stop_setup_time        = 4400,
                .bus_free_time          = 5170,
        },
        [I2C_MODE_FAST] = {
                .rate                   = 400000,
                .rep_start_hold         = 660,
                .rep_start_setup        = 660,
                .start_hold             = 660,
                .data_setup_time        = 110,
                .stop_setup_time        = 660,
                .bus_free_time          = 1430,
        },
};

static void st_i2c_flush_rx_fifo(struct st_i2c_dev *i2c_dev)
{
        int count, i;

        /*
         * Counter only counts up to 7 but fifo size is 8...
         * When fifo is full, counter is 0 and RIR bit of status register is
         * set
         */
        if (readl_relaxed(i2c_dev->base + SSC_STA) & SSC_STA_RIR)
                count = SSC_RXFIFO_SIZE;
        else
                count = readl_relaxed(i2c_dev->base + SSC_RX_FSTAT) &
                        SSC_RX_FSTAT_STATUS;

        for (i = 0; i < count; i++)
                readl_relaxed(i2c_dev->base + SSC_RBUF);
}

static void st_i2c_soft_reset(struct st_i2c_dev *i2c_dev)
{
        /*
         * FIFO needs to be emptied before reseting the IP,
         * else the controller raises a BUSY error.
         */
        st_i2c_flush_rx_fifo(i2c_dev);

        st_i2c_set_bits(i2c_dev->base + SSC_CTL, SSC_CTL_SR);
        st_i2c_clr_bits(i2c_dev->base + SSC_CTL, SSC_CTL_SR);
}

/**
 * st_i2c_hw_config() - Prepare SSC block, calculate and apply tuning timings
 * @i2c_dev: Controller's private data
 */
static void st_i2c_hw_config(struct st_i2c_dev *i2c_dev)
{
        unsigned long rate;
        u32 val, ns_per_clk;
        struct st_i2c_timings *t = &i2c_timings[i2c_dev->mode];

        st_i2c_soft_reset(i2c_dev);

        val = SSC_CLR_REPSTRT | SSC_CLR_NACK | SSC_CLR_SSCARBL |
                SSC_CLR_SSCAAS | SSC_CLR_SSCSTOP;
        writel_relaxed(val, i2c_dev->base + SSC_CLR);

        /* SSC Control register setup */
        val = SSC_CTL_PO | SSC_CTL_PH | SSC_CTL_HB | SSC_CTL_DATA_WIDTH_9;
        writel_relaxed(val, i2c_dev->base + SSC_CTL);

        rate = clk_get_rate(i2c_dev->clk);
        ns_per_clk = 1000000000 / rate;

        /* Baudrate */
        val = rate / (2 * t->rate);
        writel_relaxed(val, i2c_dev->base + SSC_BRG);

        /* Pre-scaler baudrate */
        writel_relaxed(1, i2c_dev->base + SSC_PRE_SCALER_BRG);

        /* Enable I2C mode */
        writel_relaxed(SSC_I2C_I2CM, i2c_dev->base + SSC_I2C);

        /* Repeated start hold time */
        val = t->rep_start_hold / ns_per_clk;
        writel_relaxed(val, i2c_dev->base + SSC_REP_START_HOLD);

        /* Repeated start set up time */
        val = t->rep_start_setup / ns_per_clk;
        writel_relaxed(val, i2c_dev->base + SSC_REP_START_SETUP);

        /* Start hold time */
        val = t->start_hold / ns_per_clk;
        writel_relaxed(val, i2c_dev->base + SSC_START_HOLD);

        /* Data set up time */
        val = t->data_setup_time / ns_per_clk;
        writel_relaxed(val, i2c_dev->base + SSC_DATA_SETUP);

        /* Stop set up time */
        val = t->stop_setup_time / ns_per_clk;
        writel_relaxed(val, i2c_dev->base + SSC_STOP_SETUP);

        /* Bus free time */
        val = t->bus_free_time / ns_per_clk;
        writel_relaxed(val, i2c_dev->base + SSC_BUS_FREE);

        /* Prescalers set up */
        val = rate / 10000000;
        writel_relaxed(val, i2c_dev->base + SSC_PRSCALER);
        writel_relaxed(val, i2c_dev->base + SSC_PRSCALER_DATAOUT);

        /* Noise suppression witdh */
        val = i2c_dev->scl_min_width_us * rate / 100000000;
        writel_relaxed(val, i2c_dev->base + SSC_NOISE_SUPP_WIDTH);

        /* Noise suppression max output data delay width */
        val = i2c_dev->sda_min_width_us * rate / 100000000;
        writel_relaxed(val, i2c_dev->base + SSC_NOISE_SUPP_WIDTH_DATAOUT);
}

static int st_i2c_recover_bus(struct i2c_adapter *i2c_adap)
{
        struct st_i2c_dev *i2c_dev = i2c_get_adapdata(i2c_adap);
        u32 ctl;

        dev_dbg(i2c_dev->dev, "Trying to recover bus\n");

        /*
         * SSP IP is dual role SPI/I2C to generate 9 clock pulses
         * we switch to SPI node, 9 bit words and write a 0. This
         * has been validate with a oscilloscope and is easier
         * than switching to GPIO mode.
         */

        /* Disable interrupts */
        writel_relaxed(0, i2c_dev->base + SSC_IEN);

        st_i2c_hw_config(i2c_dev);

        ctl = SSC_CTL_EN | SSC_CTL_MS | SSC_CTL_EN_RX_FIFO | SSC_CTL_EN_TX_FIFO;
        st_i2c_set_bits(i2c_dev->base + SSC_CTL, ctl);

        st_i2c_clr_bits(i2c_dev->base + SSC_I2C, SSC_I2C_I2CM);
        usleep_range(8000, 10000);

        writel_relaxed(0, i2c_dev->base + SSC_TBUF);
        usleep_range(2000, 4000);
        st_i2c_set_bits(i2c_dev->base + SSC_I2C, SSC_I2C_I2CM);

        return 0;
}

static int st_i2c_wait_free_bus(struct st_i2c_dev *i2c_dev)
{
        u32 sta;
        int i, ret;

        for (i = 0; i < 10; i++) {
                sta = readl_relaxed(i2c_dev->base + SSC_STA);
                if (!(sta & SSC_STA_BUSY))
                        return 0;

                usleep_range(2000, 4000);
        }

        dev_err(i2c_dev->dev, "bus not free (status = 0x%08x)\n", sta);

        ret = i2c_recover_bus(&i2c_dev->adap);
        if (ret) {
                dev_err(i2c_dev->dev, "Failed to recover the bus (%d)\n", ret);
                return ret;
        }

        return -EBUSY;
}

/**
 * st_i2c_write_tx_fifo() - Write a byte in the Tx FIFO
 * @i2c_dev: Controller's private data
 * @byte: Data to write in the Tx FIFO
 */
static inline void st_i2c_write_tx_fifo(struct st_i2c_dev *i2c_dev, u8 byte)
{
        u16 tbuf = byte << 1;

        writel_relaxed(tbuf | 1, i2c_dev->base + SSC_TBUF);
}

/**
 * st_i2c_wr_fill_tx_fifo() - Fill the Tx FIFO in write mode
 * @i2c_dev: Controller's private data
 *
 * This functions fills the Tx FIFO with I2C transfert buffer when
 * in write mode.
 */
static void st_i2c_wr_fill_tx_fifo(struct st_i2c_dev *i2c_dev)
{
        struct st_i2c_client *c = &i2c_dev->client;
        u32 tx_fstat, sta;
        int i;

        sta = readl_relaxed(i2c_dev->base + SSC_STA);
        if (sta & SSC_STA_TX_FIFO_FULL)
                return;

        tx_fstat = readl_relaxed(i2c_dev->base + SSC_TX_FSTAT);
        tx_fstat &= SSC_TX_FSTAT_STATUS;

        if (c->count < (SSC_TXFIFO_SIZE - tx_fstat))
                i = c->count;
        else
                i = SSC_TXFIFO_SIZE - tx_fstat;

        for (; i > 0; i--, c->count--, c->buf++)
                st_i2c_write_tx_fifo(i2c_dev, *c->buf);
}

/**
 * st_i2c_rd_fill_tx_fifo() - Fill the Tx FIFO in read mode
 * @i2c_dev: Controller's private data
 *
 * This functions fills the Tx FIFO with fixed pattern when
 * in read mode to trigger clock.
 */
static void st_i2c_rd_fill_tx_fifo(struct st_i2c_dev *i2c_dev, int max)
{
        struct st_i2c_client *c = &i2c_dev->client;
        u32 tx_fstat, sta;
        int i;

        sta = readl_relaxed(i2c_dev->base + SSC_STA);
        if (sta & SSC_STA_TX_FIFO_FULL)
                return;

        tx_fstat = readl_relaxed(i2c_dev->base + SSC_TX_FSTAT);
        tx_fstat &= SSC_TX_FSTAT_STATUS;

        if (max < (SSC_TXFIFO_SIZE - tx_fstat))
                i = max;
        else
                i = SSC_TXFIFO_SIZE - tx_fstat;

        for (; i > 0; i--, c->xfered++)
                st_i2c_write_tx_fifo(i2c_dev, 0xff);
}

static void st_i2c_read_rx_fifo(struct st_i2c_dev *i2c_dev)
{
        struct st_i2c_client *c = &i2c_dev->client;
        u32 i, sta;
        u16 rbuf;

        sta = readl_relaxed(i2c_dev->base + SSC_STA);
        if (sta & SSC_STA_RIR) {
                i = SSC_RXFIFO_SIZE;
        } else {
                i = readl_relaxed(i2c_dev->base + SSC_RX_FSTAT);
                i &= SSC_RX_FSTAT_STATUS;
        }

        for (; (i > 0) && (c->count > 0); i--, c->count--) {
                rbuf = readl_relaxed(i2c_dev->base + SSC_RBUF) >> 1;
                *c->buf++ = (u8)rbuf & 0xff;
        }

        if (i) {
                dev_err(i2c_dev->dev, "Unexpected %d bytes in rx fifo\n", i);
                st_i2c_flush_rx_fifo(i2c_dev);
        }
}

/**
 * st_i2c_terminate_xfer() - Send either STOP or REPSTART condition
 * @i2c_dev: Controller's private data
 */
static void st_i2c_terminate_xfer(struct st_i2c_dev *i2c_dev)
{
        struct st_i2c_client *c = &i2c_dev->client;

        st_i2c_clr_bits(i2c_dev->base + SSC_IEN, SSC_IEN_TEEN);
        st_i2c_clr_bits(i2c_dev->base + SSC_I2C, SSC_I2C_STRTG);

        if (c->stop) {
                st_i2c_set_bits(i2c_dev->base + SSC_IEN, SSC_IEN_STOPEN);
                st_i2c_set_bits(i2c_dev->base + SSC_I2C, SSC_I2C_STOPG);
        } else {
                st_i2c_set_bits(i2c_dev->base + SSC_IEN, SSC_IEN_REPSTRTEN);
                st_i2c_set_bits(i2c_dev->base + SSC_I2C, SSC_I2C_REPSTRTG);
        }
}

/**
 * st_i2c_handle_write() - Handle FIFO empty interrupt in case of write
 * @i2c_dev: Controller's private data
 */
static void st_i2c_handle_write(struct st_i2c_dev *i2c_dev)
{
        struct st_i2c_client *c = &i2c_dev->client;

        st_i2c_flush_rx_fifo(i2c_dev);

        if (!c->count)
                /* End of xfer, send stop or repstart */
                st_i2c_terminate_xfer(i2c_dev);
        else
                st_i2c_wr_fill_tx_fifo(i2c_dev);
}

/**
 * st_i2c_handle_write() - Handle FIFO enmpty interrupt in case of read
 * @i2c_dev: Controller's private data
 */
static void st_i2c_handle_read(struct st_i2c_dev *i2c_dev)
{
        struct st_i2c_client *c = &i2c_dev->client;
        u32 ien;

        /* Trash the address read back */
        if (!c->xfered) {
                readl_relaxed(i2c_dev->base + SSC_RBUF);
                st_i2c_clr_bits(i2c_dev->base + SSC_I2C, SSC_I2C_TXENB);
        } else {
                st_i2c_read_rx_fifo(i2c_dev);
        }

        if (!c->count) {
                /* End of xfer, send stop or repstart */
                st_i2c_terminate_xfer(i2c_dev);
        } else if (c->count == 1) {
                /* Penultimate byte to xfer, disable ACK gen. */
                st_i2c_clr_bits(i2c_dev->base + SSC_I2C, SSC_I2C_ACKG);

                /* Last received byte is to be handled by NACK interrupt */
                ien = SSC_IEN_NACKEN | SSC_IEN_ARBLEN;
                writel_relaxed(ien, i2c_dev->base + SSC_IEN);

                st_i2c_rd_fill_tx_fifo(i2c_dev, c->count);
        } else {
                st_i2c_rd_fill_tx_fifo(i2c_dev, c->count - 1);
        }
}

/**
 * st_i2c_isr() - Interrupt routine
 * @irq: interrupt number
 * @data: Controller's private data
 */
static irqreturn_t st_i2c_isr_thread(int irq, void *data)
{
        struct st_i2c_dev *i2c_dev = data;
        struct st_i2c_client *c = &i2c_dev->client;
        u32 sta, ien;
        int it;

        ien = readl_relaxed(i2c_dev->base + SSC_IEN);
        sta = readl_relaxed(i2c_dev->base + SSC_STA);

        /* Use __fls() to check error bits first */
        it = __fls(sta & ien);
        if (it < 0) {
                dev_dbg(i2c_dev->dev, "spurious it (sta=0x%04x, ien=0x%04x)\n",
                                sta, ien);
                return IRQ_NONE;
        }

        switch (1 << it) {
        case SSC_STA_TE:
                if (c->addr & I2C_M_RD)
                        st_i2c_handle_read(i2c_dev);
                else
                        st_i2c_handle_write(i2c_dev);
                break;

        case SSC_STA_STOP:
        case SSC_STA_REPSTRT:
                writel_relaxed(0, i2c_dev->base + SSC_IEN);
                complete(&i2c_dev->complete);
                break;

        case SSC_STA_NACK:
                writel_relaxed(SSC_CLR_NACK, i2c_dev->base + SSC_CLR);

                /* Last received byte handled by NACK interrupt */
                if ((c->addr & I2C_M_RD) && (c->count == 1) && (c->xfered)) {
                        st_i2c_handle_read(i2c_dev);
                        break;
                }

                it = SSC_IEN_STOPEN | SSC_IEN_ARBLEN;
                writel_relaxed(it, i2c_dev->base + SSC_IEN);

                st_i2c_set_bits(i2c_dev->base + SSC_I2C, SSC_I2C_STOPG);
                c->result = -EIO;
                break;

        case SSC_STA_ARBL:
                writel_relaxed(SSC_CLR_SSCARBL, i2c_dev->base + SSC_CLR);

                it = SSC_IEN_STOPEN | SSC_IEN_ARBLEN;
                writel_relaxed(it, i2c_dev->base + SSC_IEN);

                st_i2c_set_bits(i2c_dev->base + SSC_I2C, SSC_I2C_STOPG);
                c->result = -EAGAIN;
                break;

        default:
                dev_err(i2c_dev->dev,
                                "it %d unhandled (sta=0x%04x)\n", it, sta);
        }

        /*
         * Read IEN register to ensure interrupt mask write is effective
         * before re-enabling interrupt at GIC level, and thus avoid spurious
         * interrupts.
         */
        readl(i2c_dev->base + SSC_IEN);

        return IRQ_HANDLED;
}

/**
 * st_i2c_xfer_msg() - Transfer a single I2C message
 * @i2c_dev: Controller's private data
 * @msg: I2C message to transfer
 * @is_first: first message of the sequence
 * @is_last: last message of the sequence
 */
static int st_i2c_xfer_msg(struct st_i2c_dev *i2c_dev, struct i2c_msg *msg,
                            bool is_first, bool is_last)
{
        struct st_i2c_client *c = &i2c_dev->client;
        u32 ctl, i2c, it;
        unsigned long timeout;
        int ret;

        c->addr         = i2c_8bit_addr_from_msg(msg);
        c->buf          = msg->buf;
        c->count        = msg->len;
        c->xfered       = 0;
        c->result       = 0;
        c->stop         = is_last;

        reinit_completion(&i2c_dev->complete);

        ctl = SSC_CTL_EN | SSC_CTL_MS | SSC_CTL_EN_RX_FIFO | SSC_CTL_EN_TX_FIFO;
        st_i2c_set_bits(i2c_dev->base + SSC_CTL, ctl);

        i2c = SSC_I2C_TXENB;
        if (c->addr & I2C_M_RD)
                i2c |= SSC_I2C_ACKG;
        st_i2c_set_bits(i2c_dev->base + SSC_I2C, i2c);

        /* Write slave address */
        st_i2c_write_tx_fifo(i2c_dev, c->addr);

        /* Pre-fill Tx fifo with data in case of write */
        if (!(c->addr & I2C_M_RD))
                st_i2c_wr_fill_tx_fifo(i2c_dev);

        it = SSC_IEN_NACKEN | SSC_IEN_TEEN | SSC_IEN_ARBLEN;
        writel_relaxed(it, i2c_dev->base + SSC_IEN);

        if (is_first) {
                ret = st_i2c_wait_free_bus(i2c_dev);
                if (ret)
                        return ret;

                st_i2c_set_bits(i2c_dev->base + SSC_I2C, SSC_I2C_STRTG);
        }

        timeout = wait_for_completion_timeout(&i2c_dev->complete,
                        i2c_dev->adap.timeout);
        ret = c->result;

        if (!timeout) {
                dev_err(i2c_dev->dev, "Write to slave 0x%x timed out\n",
                                c->addr);
                ret = -ETIMEDOUT;
        }

        i2c = SSC_I2C_STOPG | SSC_I2C_REPSTRTG;
        st_i2c_clr_bits(i2c_dev->base + SSC_I2C, i2c);

        writel_relaxed(SSC_CLR_SSCSTOP | SSC_CLR_REPSTRT,
                        i2c_dev->base + SSC_CLR);

        return ret;
}

/**
 * st_i2c_xfer() - Transfer a single I2C message
 * @i2c_adap: Adapter pointer to the controller
 * @msgs: Pointer to data to be written.
 * @num: Number of messages to be executed
 */
static int st_i2c_xfer(struct i2c_adapter *i2c_adap,
                        struct i2c_msg msgs[], int num)
{
        struct st_i2c_dev *i2c_dev = i2c_get_adapdata(i2c_adap);
        int ret, i;

        i2c_dev->busy = true;

        ret = clk_prepare_enable(i2c_dev->clk);
        if (ret) {
                dev_err(i2c_dev->dev, "Failed to prepare_enable clock\n");
                return ret;
        }

        pinctrl_pm_select_default_state(i2c_dev->dev);

        st_i2c_hw_config(i2c_dev);

        for (i = 0; (i < num) && !ret; i++)
                ret = st_i2c_xfer_msg(i2c_dev, &msgs[i], i == 0, i == num - 1);

        pinctrl_pm_select_idle_state(i2c_dev->dev);

        clk_disable_unprepare(i2c_dev->clk);

        i2c_dev->busy = false;

        return (ret < 0) ? ret : i;
}

#ifdef CONFIG_PM_SLEEP
static int st_i2c_suspend(struct device *dev)
{
        struct platform_device *pdev = to_platform_device(dev);
        struct st_i2c_dev *i2c_dev = platform_get_drvdata(pdev);

        if (i2c_dev->busy)
                return -EBUSY;

        pinctrl_pm_select_sleep_state(dev);

        return 0;
}

static int st_i2c_resume(struct device *dev)
{
        pinctrl_pm_select_default_state(dev);
        /* Go in idle state if available */
        pinctrl_pm_select_idle_state(dev);

        return 0;
}

static SIMPLE_DEV_PM_OPS(st_i2c_pm, st_i2c_suspend, st_i2c_resume);
#define ST_I2C_PM       (&st_i2c_pm)
#else
#define ST_I2C_PM       NULL
#endif

static u32 st_i2c_func(struct i2c_adapter *adap)
{
        return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
}

static struct i2c_algorithm st_i2c_algo = {
        .master_xfer = st_i2c_xfer,
        .functionality = st_i2c_func,
};

static struct i2c_bus_recovery_info st_i2c_recovery_info = {
        .recover_bus = st_i2c_recover_bus,
};

static int st_i2c_of_get_deglitch(struct device_node *np,
                struct st_i2c_dev *i2c_dev)
{
        int ret;

        ret = of_property_read_u32(np, "st,i2c-min-scl-pulse-width-us",
                        &i2c_dev->scl_min_width_us);
        if ((ret == -ENODATA) || (ret == -EOVERFLOW)) {
                dev_err(i2c_dev->dev, "st,i2c-min-scl-pulse-width-us invalid\n");
                return ret;
        }

        ret = of_property_read_u32(np, "st,i2c-min-sda-pulse-width-us",
                        &i2c_dev->sda_min_width_us);
        if ((ret == -ENODATA) || (ret == -EOVERFLOW)) {
                dev_err(i2c_dev->dev, "st,i2c-min-sda-pulse-width-us invalid\n");
                return ret;
        }

        return 0;
}

static int st_i2c_probe(struct platform_device *pdev)
{
        struct device_node *np = pdev->dev.of_node;
        struct st_i2c_dev *i2c_dev;
        struct resource *res;
        u32 clk_rate;
        struct i2c_adapter *adap;
        int ret;

        i2c_dev = devm_kzalloc(&pdev->dev, sizeof(*i2c_dev), GFP_KERNEL);
        if (!i2c_dev)
                return -ENOMEM;

        res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
        i2c_dev->base = devm_ioremap_resource(&pdev->dev, res);
        if (IS_ERR(i2c_dev->base))
                return PTR_ERR(i2c_dev->base);

        i2c_dev->irq = irq_of_parse_and_map(np, 0);
        if (!i2c_dev->irq) {
                dev_err(&pdev->dev, "IRQ missing or invalid\n");
                return -EINVAL;
        }

        i2c_dev->clk = of_clk_get_by_name(np, "ssc");
        if (IS_ERR(i2c_dev->clk)) {
                dev_err(&pdev->dev, "Unable to request clock\n");
                return PTR_ERR(i2c_dev->clk);
        }

        i2c_dev->mode = I2C_MODE_STANDARD;
        ret = of_property_read_u32(np, "clock-frequency", &clk_rate);
        if ((!ret) && (clk_rate == 400000))
                i2c_dev->mode = I2C_MODE_FAST;

        i2c_dev->dev = &pdev->dev;

        ret = devm_request_threaded_irq(&pdev->dev, i2c_dev->irq,
                        NULL, st_i2c_isr_thread,
                        IRQF_ONESHOT, pdev->name, i2c_dev);
        if (ret) {
                dev_err(&pdev->dev, "Failed to request irq %i\n", i2c_dev->irq);
                return ret;
        }

        pinctrl_pm_select_default_state(i2c_dev->dev);
        /* In case idle state available, select it */
        pinctrl_pm_select_idle_state(i2c_dev->dev);

        ret = st_i2c_of_get_deglitch(np, i2c_dev);
        if (ret)
                return ret;

        adap = &i2c_dev->adap;
        i2c_set_adapdata(adap, i2c_dev);
        snprintf(adap->name, sizeof(adap->name), "ST I2C(%pa)", &res->start);
        adap->owner = THIS_MODULE;
        adap->timeout = 2 * HZ;
        adap->retries = 0;
        adap->algo = &st_i2c_algo;
        adap->bus_recovery_info = &st_i2c_recovery_info;
        adap->dev.parent = &pdev->dev;
        adap->dev.of_node = pdev->dev.of_node;

        init_completion(&i2c_dev->complete);

        ret = i2c_add_adapter(adap);
        if (ret)
                return ret;

        platform_set_drvdata(pdev, i2c_dev);

        dev_info(i2c_dev->dev, "%s initialized\n", adap->name);

        return 0;
}

static int st_i2c_remove(struct platform_device *pdev)
{
        struct st_i2c_dev *i2c_dev = platform_get_drvdata(pdev);

        i2c_del_adapter(&i2c_dev->adap);

        return 0;
}

static const struct of_device_id st_i2c_match[] = {
        { .compatible = "st,comms-ssc-i2c", },
        { .compatible = "st,comms-ssc4-i2c", },
        {},
};
MODULE_DEVICE_TABLE(of, st_i2c_match);

static struct platform_driver st_i2c_driver = {
        .driver = {
                .name = "st-i2c",
                .of_match_table = st_i2c_match,
                .pm = ST_I2C_PM,
        },
        .probe = st_i2c_probe,
        .remove = st_i2c_remove,
};

module_platform_driver(st_i2c_driver);

MODULE_AUTHOR("Maxime Coquelin <maxime.coquelin@st.com>");
MODULE_DESCRIPTION("STMicroelectronics I2C driver");
MODULE_LICENSE("GPL v2");