/*
 * Driver for STMicroelectronics STM32 I2C controller
 *
 * This I2C controller is described in the STM32F429/439 Soc reference manual.
 * Please see below a link to the documentation:
 * http://www.st.com/resource/en/reference_manual/DM00031020.pdf
 *
 * Copyright (C) M'boumba Cedric Madianga 2016
 * Author: M'boumba Cedric Madianga <cedric.madianga@gmail.com>
 *
 * This driver is based on i2c-st.c
 *
 * License terms:  GNU General Public License (GPL), version 2
 */

#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/iopoll.h>
#include <linux/module.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/reset.h>

#include "i2c-stm32.h"

/* STM32F4 I2C offset registers */
#define STM32F4_I2C_CR1                 0x00
#define STM32F4_I2C_CR2                 0x04
#define STM32F4_I2C_DR                  0x10
#define STM32F4_I2C_SR1                 0x14
#define STM32F4_I2C_SR2                 0x18
#define STM32F4_I2C_CCR                 0x1C
#define STM32F4_I2C_TRISE               0x20
#define STM32F4_I2C_FLTR                0x24

/* STM32F4 I2C control 1*/
#define STM32F4_I2C_CR1_POS             BIT(11)
#define STM32F4_I2C_CR1_ACK             BIT(10)
#define STM32F4_I2C_CR1_STOP            BIT(9)
#define STM32F4_I2C_CR1_START           BIT(8)
#define STM32F4_I2C_CR1_PE              BIT(0)

/* STM32F4 I2C control 2 */
#define STM32F4_I2C_CR2_FREQ_MASK       GENMASK(5, 0)
#define STM32F4_I2C_CR2_FREQ(n)         ((n) & STM32F4_I2C_CR2_FREQ_MASK)
#define STM32F4_I2C_CR2_ITBUFEN         BIT(10)
#define STM32F4_I2C_CR2_ITEVTEN         BIT(9)
#define STM32F4_I2C_CR2_ITERREN         BIT(8)
#define STM32F4_I2C_CR2_IRQ_MASK        (STM32F4_I2C_CR2_ITBUFEN | \
                                         STM32F4_I2C_CR2_ITEVTEN | \
                                         STM32F4_I2C_CR2_ITERREN)

/* STM32F4 I2C Status 1 */
#define STM32F4_I2C_SR1_AF              BIT(10)
#define STM32F4_I2C_SR1_ARLO            BIT(9)
#define STM32F4_I2C_SR1_BERR            BIT(8)
#define STM32F4_I2C_SR1_TXE             BIT(7)
#define STM32F4_I2C_SR1_RXNE            BIT(6)
#define STM32F4_I2C_SR1_BTF             BIT(2)
#define STM32F4_I2C_SR1_ADDR            BIT(1)
#define STM32F4_I2C_SR1_SB              BIT(0)
#define STM32F4_I2C_SR1_ITEVTEN_MASK    (STM32F4_I2C_SR1_BTF | \
                                         STM32F4_I2C_SR1_ADDR | \
                                         STM32F4_I2C_SR1_SB)
#define STM32F4_I2C_SR1_ITBUFEN_MASK    (STM32F4_I2C_SR1_TXE | \
                                         STM32F4_I2C_SR1_RXNE)
#define STM32F4_I2C_SR1_ITERREN_MASK    (STM32F4_I2C_SR1_AF | \
                                         STM32F4_I2C_SR1_ARLO | \
                                         STM32F4_I2C_SR1_BERR)

/* STM32F4 I2C Status 2 */
#define STM32F4_I2C_SR2_BUSY            BIT(1)

/* STM32F4 I2C Control Clock */
#define STM32F4_I2C_CCR_CCR_MASK        GENMASK(11, 0)
#define STM32F4_I2C_CCR_CCR(n)          ((n) & STM32F4_I2C_CCR_CCR_MASK)
#define STM32F4_I2C_CCR_FS              BIT(15)
#define STM32F4_I2C_CCR_DUTY            BIT(14)

/* STM32F4 I2C Trise */
#define STM32F4_I2C_TRISE_VALUE_MASK    GENMASK(5, 0)
#define STM32F4_I2C_TRISE_VALUE(n)      ((n) & STM32F4_I2C_TRISE_VALUE_MASK)

#define STM32F4_I2C_MIN_STANDARD_FREQ   2U
#define STM32F4_I2C_MIN_FAST_FREQ       6U
#define STM32F4_I2C_MAX_FREQ            46U
#define HZ_TO_MHZ                       1000000

/**
 * struct stm32f4_i2c_msg - client specific data
 * @addr: 8-bit slave addr, including r/w bit
 * @count: number of bytes to be transferred
 * @buf: data buffer
 * @result: result of the transfer
 * @stop: last I2C msg to be sent, i.e. STOP to be generated
 */
struct stm32f4_i2c_msg {
        u8 addr;
        u32 count;
        u8 *buf;
        int result;
        bool stop;
};

/**
 * struct stm32f4_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
 * @clk: hw i2c clock
 * @speed: I2C clock frequency of the controller. Standard or Fast are supported
 * @parent_rate: I2C clock parent rate in MHz
 * @msg: I2C transfer information
 */
struct stm32f4_i2c_dev {
        struct i2c_adapter adap;
        struct device *dev;
        void __iomem *base;
        struct completion complete;
        struct clk *clk;
        int speed;
        int parent_rate;
        struct stm32f4_i2c_msg msg;
};

static inline void stm32f4_i2c_set_bits(void __iomem *reg, u32 mask)
{
        writel_relaxed(readl_relaxed(reg) | mask, reg);
}

static inline void stm32f4_i2c_clr_bits(void __iomem *reg, u32 mask)
{
        writel_relaxed(readl_relaxed(reg) & ~mask, reg);
}

static void stm32f4_i2c_disable_irq(struct stm32f4_i2c_dev *i2c_dev)
{
        void __iomem *reg = i2c_dev->base + STM32F4_I2C_CR2;

        stm32f4_i2c_clr_bits(reg, STM32F4_I2C_CR2_IRQ_MASK);
}

static int stm32f4_i2c_set_periph_clk_freq(struct stm32f4_i2c_dev *i2c_dev)
{
        u32 freq;
        u32 cr2 = 0;

        i2c_dev->parent_rate = clk_get_rate(i2c_dev->clk);
        freq = DIV_ROUND_UP(i2c_dev->parent_rate, HZ_TO_MHZ);

        if (i2c_dev->speed == STM32_I2C_SPEED_STANDARD) {
                /*
                 * To reach 100 kHz, the parent clk frequency should be between
                 * a minimum value of 2 MHz and a maximum value of 46 MHz due
                 * to hardware limitation
                 */
                if (freq < STM32F4_I2C_MIN_STANDARD_FREQ ||
                    freq > STM32F4_I2C_MAX_FREQ) {
                        dev_err(i2c_dev->dev,
                                "bad parent clk freq for standard mode\n");
                        return -EINVAL;
                }
        } else {
                /*
                 * To be as close as possible to 400 kHz, the parent clk
                 * frequency should be between a minimum value of 6 MHz and a
                 * maximum value of 46 MHz due to hardware limitation
                 */
                if (freq < STM32F4_I2C_MIN_FAST_FREQ ||
                    freq > STM32F4_I2C_MAX_FREQ) {
                        dev_err(i2c_dev->dev,
                                "bad parent clk freq for fast mode\n");
                        return -EINVAL;
                }
        }

        cr2 |= STM32F4_I2C_CR2_FREQ(freq);
        writel_relaxed(cr2, i2c_dev->base + STM32F4_I2C_CR2);

        return 0;
}

static void stm32f4_i2c_set_rise_time(struct stm32f4_i2c_dev *i2c_dev)
{
        u32 freq = DIV_ROUND_UP(i2c_dev->parent_rate, HZ_TO_MHZ);
        u32 trise;

        /*
         * These bits must be programmed with the maximum SCL rise time given in
         * the I2C bus specification, incremented by 1.
         *
         * In standard mode, the maximum allowed SCL rise time is 1000 ns.
         * If, in the I2C_CR2 register, the value of FREQ[5:0] bits is equal to
         * 0x08 so period = 125 ns therefore the TRISE[5:0] bits must be
         * programmed with 0x9. (1000 ns / 125 ns + 1)
         * So, for I2C standard mode TRISE = FREQ[5:0] + 1
         *
         * In fast mode, the maximum allowed SCL rise time is 300 ns.
         * If, in the I2C_CR2 register, the value of FREQ[5:0] bits is equal to
         * 0x08 so period = 125 ns therefore the TRISE[5:0] bits must be
         * programmed with 0x3. (300 ns / 125 ns + 1)
         * So, for I2C fast mode TRISE = FREQ[5:0] * 300 / 1000 + 1
         *
         * Function stm32f4_i2c_set_periph_clk_freq made sure that parent rate
         * is not higher than 46 MHz . As a result trise is at most 4 bits wide
         * and so fits into the TRISE bits [5:0].
         */
        if (i2c_dev->speed == STM32_I2C_SPEED_STANDARD)
                trise = freq + 1;
        else
                trise = freq * 3 / 10 + 1;

        writel_relaxed(STM32F4_I2C_TRISE_VALUE(trise),
                       i2c_dev->base + STM32F4_I2C_TRISE);
}

static void stm32f4_i2c_set_speed_mode(struct stm32f4_i2c_dev *i2c_dev)
{
        u32 val;
        u32 ccr = 0;

        if (i2c_dev->speed == STM32_I2C_SPEED_STANDARD) {
                /*
                 * In standard mode:
                 * t_scl_high = t_scl_low = CCR * I2C parent clk period
                 * So to reach 100 kHz, we have:
                 * CCR = I2C parent rate / 100 kHz >> 1
                 *
                 * For example with parent rate = 2 MHz:
                 * CCR = 2000000 / (100000 << 1) = 10
                 * t_scl_high = t_scl_low = 10 * (1 / 2000000) = 5000 ns
                 * t_scl_high + t_scl_low = 10000 ns so 100 kHz is reached
                 *
                 * Function stm32f4_i2c_set_periph_clk_freq made sure that
                 * parent rate is not higher than 46 MHz . As a result val
                 * is at most 8 bits wide and so fits into the CCR bits [11:0].
                 */
                val = i2c_dev->parent_rate / (100000 << 1);
        } else {
                /*
                 * In fast mode, we compute CCR with duty = 0 as with low
                 * frequencies we are not able to reach 400 kHz.
                 * In that case:
                 * t_scl_high = CCR * I2C parent clk period
                 * t_scl_low = 2 * CCR * I2C parent clk period
                 * So, CCR = I2C parent rate / (400 kHz * 3)
                 *
                 * For example with parent rate = 6 MHz:
                 * CCR = 6000000 / (400000 * 3) = 5
                 * t_scl_high = 5 * (1 / 6000000) = 833 ns > 600 ns
                 * t_scl_low = 2 * 5 * (1 / 6000000) = 1667 ns > 1300 ns
                 * t_scl_high + t_scl_low = 2500 ns so 400 kHz is reached
                 *
                 * Function stm32f4_i2c_set_periph_clk_freq made sure that
                 * parent rate is not higher than 46 MHz . As a result val
                 * is at most 6 bits wide and so fits into the CCR bits [11:0].
                 */
                val = DIV_ROUND_UP(i2c_dev->parent_rate, 400000 * 3);

                /* Select Fast mode */
                ccr |= STM32F4_I2C_CCR_FS;
        }

        ccr |= STM32F4_I2C_CCR_CCR(val);
        writel_relaxed(ccr, i2c_dev->base + STM32F4_I2C_CCR);
}

/**
 * stm32f4_i2c_hw_config() - Prepare I2C block
 * @i2c_dev: Controller's private data
 */
static int stm32f4_i2c_hw_config(struct stm32f4_i2c_dev *i2c_dev)
{
        int ret;

        ret = stm32f4_i2c_set_periph_clk_freq(i2c_dev);
        if (ret)
                return ret;

        stm32f4_i2c_set_rise_time(i2c_dev);

        stm32f4_i2c_set_speed_mode(i2c_dev);

        /* Enable I2C */
        writel_relaxed(STM32F4_I2C_CR1_PE, i2c_dev->base + STM32F4_I2C_CR1);

        return 0;
}

static int stm32f4_i2c_wait_free_bus(struct stm32f4_i2c_dev *i2c_dev)
{
        u32 status;
        int ret;

        ret = readl_relaxed_poll_timeout(i2c_dev->base + STM32F4_I2C_SR2,
                                         status,
                                         !(status & STM32F4_I2C_SR2_BUSY),
                                         10, 1000);
        if (ret) {
                dev_dbg(i2c_dev->dev, "bus not free\n");
                ret = -EBUSY;
        }

        return ret;
}

/**
 * stm32f4_i2c_write_ byte() - Write a byte in the data register
 * @i2c_dev: Controller's private data
 * @byte: Data to write in the register
 */
static void stm32f4_i2c_write_byte(struct stm32f4_i2c_dev *i2c_dev, u8 byte)
{
        writel_relaxed(byte, i2c_dev->base + STM32F4_I2C_DR);
}

/**
 * stm32f4_i2c_write_msg() - Fill the data register in write mode
 * @i2c_dev: Controller's private data
 *
 * This function fills the data register with I2C transfer buffer
 */
static void stm32f4_i2c_write_msg(struct stm32f4_i2c_dev *i2c_dev)
{
        struct stm32f4_i2c_msg *msg = &i2c_dev->msg;

        stm32f4_i2c_write_byte(i2c_dev, *msg->buf++);
        msg->count--;
}

static void stm32f4_i2c_read_msg(struct stm32f4_i2c_dev *i2c_dev)
{
        struct stm32f4_i2c_msg *msg = &i2c_dev->msg;
        u32 rbuf;

        rbuf = readl_relaxed(i2c_dev->base + STM32F4_I2C_DR);
        *msg->buf++ = rbuf;
        msg->count--;
}

static void stm32f4_i2c_terminate_xfer(struct stm32f4_i2c_dev *i2c_dev)
{
        struct stm32f4_i2c_msg *msg = &i2c_dev->msg;
        void __iomem *reg = i2c_dev->base + STM32F4_I2C_CR2;

        stm32f4_i2c_disable_irq(i2c_dev);

        reg = i2c_dev->base + STM32F4_I2C_CR1;
        if (msg->stop)
                stm32f4_i2c_set_bits(reg, STM32F4_I2C_CR1_STOP);
        else
                stm32f4_i2c_set_bits(reg, STM32F4_I2C_CR1_START);

        complete(&i2c_dev->complete);
}

/**
 * stm32f4_i2c_handle_write() - Handle FIFO empty interrupt in case of write
 * @i2c_dev: Controller's private data
 */
static void stm32f4_i2c_handle_write(struct stm32f4_i2c_dev *i2c_dev)
{
        struct stm32f4_i2c_msg *msg = &i2c_dev->msg;
        void __iomem *reg = i2c_dev->base + STM32F4_I2C_CR2;

        if (msg->count) {
                stm32f4_i2c_write_msg(i2c_dev);
                if (!msg->count) {
                        /*
                         * Disable buffer interrupts for RX not empty and TX
                         * empty events
                         */
                        stm32f4_i2c_clr_bits(reg, STM32F4_I2C_CR2_ITBUFEN);
                }
        } else {
                stm32f4_i2c_terminate_xfer(i2c_dev);
        }
}

/**
 * stm32f4_i2c_handle_read() - Handle FIFO empty interrupt in case of read
 * @i2c_dev: Controller's private data
 *
 * This function is called when a new data is received in data register
 */
static void stm32f4_i2c_handle_read(struct stm32f4_i2c_dev *i2c_dev)
{
        struct stm32f4_i2c_msg *msg = &i2c_dev->msg;
        void __iomem *reg = i2c_dev->base + STM32F4_I2C_CR2;

        switch (msg->count) {
        case 1:
                stm32f4_i2c_disable_irq(i2c_dev);
                stm32f4_i2c_read_msg(i2c_dev);
                complete(&i2c_dev->complete);
                break;
        /*
         * For 2-byte reception, 3-byte reception and for Data N-2, N-1 and N
         * for N-byte reception with N > 3, we do not have to read the data
         * register when RX not empty event occurs as we have to wait for byte
         * transferred finished event before reading data.
         * So, here we just disable buffer interrupt in order to avoid another
         * system preemption due to RX not empty event.
         */
        case 2:
        case 3:
                stm32f4_i2c_clr_bits(reg, STM32F4_I2C_CR2_ITBUFEN);
                break;
        /*
         * For N byte reception with N > 3 we directly read data register
         * until N-2 data.
         */
        default:
                stm32f4_i2c_read_msg(i2c_dev);
        }
}

/**
 * stm32f4_i2c_handle_rx_done() - Handle byte transfer finished interrupt
 * in case of read
 * @i2c_dev: Controller's private data
 *
 * This function is called when a new data is received in the shift register
 * but data register has not been read yet.
 */
static void stm32f4_i2c_handle_rx_done(struct stm32f4_i2c_dev *i2c_dev)
{
        struct stm32f4_i2c_msg *msg = &i2c_dev->msg;
        void __iomem *reg;
        u32 mask;
        int i;

        switch (msg->count) {
        case 2:
                /*
                 * In order to correctly send the Stop or Repeated Start
                 * condition on the I2C bus, the STOP/START bit has to be set
                 * before reading the last two bytes (data N-1 and N).
                 * After that, we could read the last two bytes, disable
                 * remaining interrupts and notify the end of xfer to the
                 * client
                 */
                reg = i2c_dev->base + STM32F4_I2C_CR1;
                if (msg->stop)
                        stm32f4_i2c_set_bits(reg, STM32F4_I2C_CR1_STOP);
                else
                        stm32f4_i2c_set_bits(reg, STM32F4_I2C_CR1_START);

                for (i = 2; i > 0; i--)
                        stm32f4_i2c_read_msg(i2c_dev);

                reg = i2c_dev->base + STM32F4_I2C_CR2;
                mask = STM32F4_I2C_CR2_ITEVTEN | STM32F4_I2C_CR2_ITERREN;
                stm32f4_i2c_clr_bits(reg, mask);

                complete(&i2c_dev->complete);
                break;
        case 3:
                /*
                 * In order to correctly generate the NACK pulse after the last
                 * received data byte, we have to enable NACK before reading N-2
                 * data
                 */
                reg = i2c_dev->base + STM32F4_I2C_CR1;
                stm32f4_i2c_clr_bits(reg, STM32F4_I2C_CR1_ACK);
                stm32f4_i2c_read_msg(i2c_dev);
                break;
        default:
                stm32f4_i2c_read_msg(i2c_dev);
        }
}

/**
 * stm32f4_i2c_handle_rx_addr() - Handle address matched interrupt in case of
 * master receiver
 * @i2c_dev: Controller's private data
 */
static void stm32f4_i2c_handle_rx_addr(struct stm32f4_i2c_dev *i2c_dev)
{
        struct stm32f4_i2c_msg *msg = &i2c_dev->msg;
        u32 cr1;

        switch (msg->count) {
        case 0:
                stm32f4_i2c_terminate_xfer(i2c_dev);

                /* Clear ADDR flag */
                readl_relaxed(i2c_dev->base + STM32F4_I2C_SR2);
                break;
        case 1:
                /*
                 * Single byte reception:
                 * Enable NACK and reset POS (Acknowledge position).
                 * Then, clear ADDR flag and set STOP or RepSTART.
                 * In that way, the NACK and STOP or RepStart pulses will be
                 * sent as soon as the byte will be received in shift register
                 */
                cr1 = readl_relaxed(i2c_dev->base + STM32F4_I2C_CR1);
                cr1 &= ~(STM32F4_I2C_CR1_ACK | STM32F4_I2C_CR1_POS);
                writel_relaxed(cr1, i2c_dev->base + STM32F4_I2C_CR1);

                readl_relaxed(i2c_dev->base + STM32F4_I2C_SR2);

                if (msg->stop)
                        cr1 |= STM32F4_I2C_CR1_STOP;
                else
                        cr1 |= STM32F4_I2C_CR1_START;
                writel_relaxed(cr1, i2c_dev->base + STM32F4_I2C_CR1);
                break;
        case 2:
                /*
                 * 2-byte reception:
                 * Enable NACK, set POS (NACK position) and clear ADDR flag.
                 * In that way, NACK will be sent for the next byte which will
                 * be received in the shift register instead of the current
                 * one.
                 */
                cr1 = readl_relaxed(i2c_dev->base + STM32F4_I2C_CR1);
                cr1 &= ~STM32F4_I2C_CR1_ACK;
                cr1 |= STM32F4_I2C_CR1_POS;
                writel_relaxed(cr1, i2c_dev->base + STM32F4_I2C_CR1);

                readl_relaxed(i2c_dev->base + STM32F4_I2C_SR2);
                break;

        default:
                /*
                 * N-byte reception:
                 * Enable ACK, reset POS (ACK postion) and clear ADDR flag.
                 * In that way, ACK will be sent as soon as the current byte
                 * will be received in the shift register
                 */
                cr1 = readl_relaxed(i2c_dev->base + STM32F4_I2C_CR1);
                cr1 |= STM32F4_I2C_CR1_ACK;
                cr1 &= ~STM32F4_I2C_CR1_POS;
                writel_relaxed(cr1, i2c_dev->base + STM32F4_I2C_CR1);

                readl_relaxed(i2c_dev->base + STM32F4_I2C_SR2);
                break;
        }
}

/**
 * stm32f4_i2c_isr_event() - Interrupt routine for I2C bus event
 * @irq: interrupt number
 * @data: Controller's private data
 */
static irqreturn_t stm32f4_i2c_isr_event(int irq, void *data)
{
        struct stm32f4_i2c_dev *i2c_dev = data;
        struct stm32f4_i2c_msg *msg = &i2c_dev->msg;
        u32 possible_status = STM32F4_I2C_SR1_ITEVTEN_MASK;
        u32 status, ien, event, cr2;

        cr2 = readl_relaxed(i2c_dev->base + STM32F4_I2C_CR2);
        ien = cr2 & STM32F4_I2C_CR2_IRQ_MASK;

        /* Update possible_status if buffer interrupt is enabled */
        if (ien & STM32F4_I2C_CR2_ITBUFEN)
                possible_status |= STM32F4_I2C_SR1_ITBUFEN_MASK;

        status = readl_relaxed(i2c_dev->base + STM32F4_I2C_SR1);
        event = status & possible_status;
        if (!event) {
                dev_dbg(i2c_dev->dev,
                        "spurious evt irq (status=0x%08x, ien=0x%08x)\n",
                        status, ien);
                return IRQ_NONE;
        }

        /* Start condition generated */
        if (event & STM32F4_I2C_SR1_SB)
                stm32f4_i2c_write_byte(i2c_dev, msg->addr);

        /* I2C Address sent */
        if (event & STM32F4_I2C_SR1_ADDR) {
                if (msg->addr & I2C_M_RD)
                        stm32f4_i2c_handle_rx_addr(i2c_dev);
                else
                        readl_relaxed(i2c_dev->base + STM32F4_I2C_SR2);

                /*
                 * Enable buffer interrupts for RX not empty and TX empty
                 * events
                 */
                cr2 |= STM32F4_I2C_CR2_ITBUFEN;
                writel_relaxed(cr2, i2c_dev->base + STM32F4_I2C_CR2);
        }

        /* TX empty */
        if ((event & STM32F4_I2C_SR1_TXE) && !(msg->addr & I2C_M_RD))
                stm32f4_i2c_handle_write(i2c_dev);

        /* RX not empty */
        if ((event & STM32F4_I2C_SR1_RXNE) && (msg->addr & I2C_M_RD))
                stm32f4_i2c_handle_read(i2c_dev);

        /*
         * The BTF (Byte Transfer finished) event occurs when:
         * - in reception : a new byte is received in the shift register
         * but the previous byte has not been read yet from data register
         * - in transmission: a new byte should be sent but the data register
         * has not been written yet
         */
        if (event & STM32F4_I2C_SR1_BTF) {
                if (msg->addr & I2C_M_RD)
                        stm32f4_i2c_handle_rx_done(i2c_dev);
                else
                        stm32f4_i2c_handle_write(i2c_dev);
        }

        return IRQ_HANDLED;
}

/**
 * stm32f4_i2c_isr_error() - Interrupt routine for I2C bus error
 * @irq: interrupt number
 * @data: Controller's private data
 */
static irqreturn_t stm32f4_i2c_isr_error(int irq, void *data)
{
        struct stm32f4_i2c_dev *i2c_dev = data;
        struct stm32f4_i2c_msg *msg = &i2c_dev->msg;
        void __iomem *reg;
        u32 status;

        status = readl_relaxed(i2c_dev->base + STM32F4_I2C_SR1);

        /* Arbitration lost */
        if (status & STM32F4_I2C_SR1_ARLO) {
                status &= ~STM32F4_I2C_SR1_ARLO;
                writel_relaxed(status, i2c_dev->base + STM32F4_I2C_SR1);
                msg->result = -EAGAIN;
        }

        /*
         * Acknowledge failure:
         * In master transmitter mode a Stop must be generated by software
         */
        if (status & STM32F4_I2C_SR1_AF) {
                if (!(msg->addr & I2C_M_RD)) {
                        reg = i2c_dev->base + STM32F4_I2C_CR1;
                        stm32f4_i2c_set_bits(reg, STM32F4_I2C_CR1_STOP);
                }
                status &= ~STM32F4_I2C_SR1_AF;
                writel_relaxed(status, i2c_dev->base + STM32F4_I2C_SR1);
                msg->result = -EIO;
        }

        /* Bus error */
        if (status & STM32F4_I2C_SR1_BERR) {
                status &= ~STM32F4_I2C_SR1_BERR;
                writel_relaxed(status, i2c_dev->base + STM32F4_I2C_SR1);
                msg->result = -EIO;
        }

        stm32f4_i2c_disable_irq(i2c_dev);
        complete(&i2c_dev->complete);

        return IRQ_HANDLED;
}

/**
 * stm32f4_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 stm32f4_i2c_xfer_msg(struct stm32f4_i2c_dev *i2c_dev,
                                struct i2c_msg *msg, bool is_first,
                                bool is_last)
{
        struct stm32f4_i2c_msg *f4_msg = &i2c_dev->msg;
        void __iomem *reg = i2c_dev->base + STM32F4_I2C_CR1;
        unsigned long timeout;
        u32 mask;
        int ret;

        f4_msg->addr = i2c_8bit_addr_from_msg(msg);
        f4_msg->buf = msg->buf;
        f4_msg->count = msg->len;
        f4_msg->result = 0;
        f4_msg->stop = is_last;

        reinit_completion(&i2c_dev->complete);

        /* Enable events and errors interrupts */
        mask = STM32F4_I2C_CR2_ITEVTEN | STM32F4_I2C_CR2_ITERREN;
        stm32f4_i2c_set_bits(i2c_dev->base + STM32F4_I2C_CR2, mask);

        if (is_first) {
                ret = stm32f4_i2c_wait_free_bus(i2c_dev);
                if (ret)
                        return ret;

                /* START generation */
                stm32f4_i2c_set_bits(reg, STM32F4_I2C_CR1_START);
        }

        timeout = wait_for_completion_timeout(&i2c_dev->complete,
                                              i2c_dev->adap.timeout);
        ret = f4_msg->result;

        if (!timeout)
                ret = -ETIMEDOUT;

        return ret;
}

/**
 * stm32f4_i2c_xfer() - Transfer combined 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 stm32f4_i2c_xfer(struct i2c_adapter *i2c_adap, struct i2c_msg msgs[],
                            int num)
{
        struct stm32f4_i2c_dev *i2c_dev = i2c_get_adapdata(i2c_adap);
        int ret, i;

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

        for (i = 0; i < num && !ret; i++)
                ret = stm32f4_i2c_xfer_msg(i2c_dev, &msgs[i], i == 0,
                                           i == num - 1);

        clk_disable(i2c_dev->clk);

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

static u32 stm32f4_i2c_func(struct i2c_adapter *adap)
{
        return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
}

static const struct i2c_algorithm stm32f4_i2c_algo = {
        .master_xfer = stm32f4_i2c_xfer,
        .functionality = stm32f4_i2c_func,
};

static int stm32f4_i2c_probe(struct platform_device *pdev)
{
        struct device_node *np = pdev->dev.of_node;
        struct stm32f4_i2c_dev *i2c_dev;
        struct resource *res;
        u32 irq_event, irq_error, clk_rate;
        struct i2c_adapter *adap;
        struct reset_control *rst;
        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);

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

        irq_error = irq_of_parse_and_map(np, 1);
        if (!irq_error) {
                dev_err(&pdev->dev, "IRQ error missing or invalid\n");
                return -EINVAL;
        }

        i2c_dev->clk = devm_clk_get(&pdev->dev, NULL);
        if (IS_ERR(i2c_dev->clk)) {
                dev_err(&pdev->dev, "Error: Missing controller clock\n");
                return PTR_ERR(i2c_dev->clk);
        }
        ret = clk_prepare_enable(i2c_dev->clk);
        if (ret) {
                dev_err(i2c_dev->dev, "Failed to prepare_enable clock\n");
                return ret;
        }

        rst = devm_reset_control_get_exclusive(&pdev->dev, NULL);
        if (IS_ERR(rst)) {
                dev_err(&pdev->dev, "Error: Missing controller reset\n");
                ret = PTR_ERR(rst);
                goto clk_free;
        }
        reset_control_assert(rst);
        udelay(2);
        reset_control_deassert(rst);

        i2c_dev->speed = STM32_I2C_SPEED_STANDARD;
        ret = of_property_read_u32(np, "clock-frequency", &clk_rate);
        if (!ret && clk_rate >= 400000)
                i2c_dev->speed = STM32_I2C_SPEED_FAST;

        i2c_dev->dev = &pdev->dev;

        ret = devm_request_irq(&pdev->dev, irq_event, stm32f4_i2c_isr_event, 0,
                               pdev->name, i2c_dev);
        if (ret) {
                dev_err(&pdev->dev, "Failed to request irq event %i\n",
                        irq_event);
                goto clk_free;
        }

        ret = devm_request_irq(&pdev->dev, irq_error, stm32f4_i2c_isr_error, 0,
                               pdev->name, i2c_dev);
        if (ret) {
                dev_err(&pdev->dev, "Failed to request irq error %i\n",
                        irq_error);
                goto clk_free;
        }

        ret = stm32f4_i2c_hw_config(i2c_dev);
        if (ret)
                goto clk_free;

        adap = &i2c_dev->adap;
        i2c_set_adapdata(adap, i2c_dev);
        snprintf(adap->name, sizeof(adap->name), "STM32 I2C(%pa)", &res->start);
        adap->owner = THIS_MODULE;
        adap->timeout = 2 * HZ;
        adap->retries = 0;
        adap->algo = &stm32f4_i2c_algo;
        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)
                goto clk_free;

        platform_set_drvdata(pdev, i2c_dev);

        clk_disable(i2c_dev->clk);

        dev_info(i2c_dev->dev, "STM32F4 I2C driver registered\n");

        return 0;

clk_free:
        clk_disable_unprepare(i2c_dev->clk);
        return ret;
}

static int stm32f4_i2c_remove(struct platform_device *pdev)
{
        struct stm32f4_i2c_dev *i2c_dev = platform_get_drvdata(pdev);

        i2c_del_adapter(&i2c_dev->adap);

        clk_unprepare(i2c_dev->clk);

        return 0;
}

static const struct of_device_id stm32f4_i2c_match[] = {
        { .compatible = "st,stm32f4-i2c", },
        {},
};
MODULE_DEVICE_TABLE(of, stm32f4_i2c_match);

static struct platform_driver stm32f4_i2c_driver = {
        .driver = {
                .name = "stm32f4-i2c",
                .of_match_table = stm32f4_i2c_match,
        },
        .probe = stm32f4_i2c_probe,
        .remove = stm32f4_i2c_remove,
};

module_platform_driver(stm32f4_i2c_driver);

MODULE_AUTHOR("M'boumba Cedric Madianga <cedric.madianga@gmail.com>");
MODULE_DESCRIPTION("STMicroelectronics STM32F4 I2C driver");
MODULE_LICENSE("GPL v2");