/*
 * Driver for STMicroelectronics STM32F7 I2C controller
 *
 * This I2C controller is described in the STM32F75xxx and STM32F74xxx Soc
 * reference manual.
 * Please see below a link to the documentation:
 * http://www.st.com/resource/en/reference_manual/dm00124865.pdf
 *
 * Copyright (C) M'boumba Cedric Madianga 2017
 * Author: M'boumba Cedric Madianga <cedric.madianga@gmail.com>
 *
 * This driver is based on i2c-stm32f4.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.h>
#include <linux/of_address.h>
#include <linux/of_irq.h>
#include <linux/of_platform.h>
#include <linux/platform_device.h>
#include <linux/reset.h>
#include <linux/slab.h>

#include "i2c-stm32.h"

/* STM32F7 I2C registers */
#define STM32F7_I2C_CR1                         0x00
#define STM32F7_I2C_CR2                         0x04
#define STM32F7_I2C_TIMINGR                     0x10
#define STM32F7_I2C_ISR                         0x18
#define STM32F7_I2C_ICR                         0x1C
#define STM32F7_I2C_RXDR                        0x24
#define STM32F7_I2C_TXDR                        0x28

/* STM32F7 I2C control 1 */
#define STM32F7_I2C_CR1_ANFOFF                  BIT(12)
#define STM32F7_I2C_CR1_ERRIE                   BIT(7)
#define STM32F7_I2C_CR1_TCIE                    BIT(6)
#define STM32F7_I2C_CR1_STOPIE                  BIT(5)
#define STM32F7_I2C_CR1_NACKIE                  BIT(4)
#define STM32F7_I2C_CR1_ADDRIE                  BIT(3)
#define STM32F7_I2C_CR1_RXIE                    BIT(2)
#define STM32F7_I2C_CR1_TXIE                    BIT(1)
#define STM32F7_I2C_CR1_PE                      BIT(0)
#define STM32F7_I2C_ALL_IRQ_MASK                (STM32F7_I2C_CR1_ERRIE \
                                                | STM32F7_I2C_CR1_TCIE \
                                                | STM32F7_I2C_CR1_STOPIE \
                                                | STM32F7_I2C_CR1_NACKIE \
                                                | STM32F7_I2C_CR1_RXIE \
                                                | STM32F7_I2C_CR1_TXIE)

/* STM32F7 I2C control 2 */
#define STM32F7_I2C_CR2_RELOAD                  BIT(24)
#define STM32F7_I2C_CR2_NBYTES_MASK             GENMASK(23, 16)
#define STM32F7_I2C_CR2_NBYTES(n)               (((n) & 0xff) << 16)
#define STM32F7_I2C_CR2_NACK                    BIT(15)
#define STM32F7_I2C_CR2_STOP                    BIT(14)
#define STM32F7_I2C_CR2_START                   BIT(13)
#define STM32F7_I2C_CR2_RD_WRN                  BIT(10)
#define STM32F7_I2C_CR2_SADD7_MASK              GENMASK(7, 1)
#define STM32F7_I2C_CR2_SADD7(n)                (((n) & 0x7f) << 1)

/* STM32F7 I2C Interrupt Status */
#define STM32F7_I2C_ISR_BUSY                    BIT(15)
#define STM32F7_I2C_ISR_ARLO                    BIT(9)
#define STM32F7_I2C_ISR_BERR                    BIT(8)
#define STM32F7_I2C_ISR_TCR                     BIT(7)
#define STM32F7_I2C_ISR_TC                      BIT(6)
#define STM32F7_I2C_ISR_STOPF                   BIT(5)
#define STM32F7_I2C_ISR_NACKF                   BIT(4)
#define STM32F7_I2C_ISR_RXNE                    BIT(2)
#define STM32F7_I2C_ISR_TXIS                    BIT(1)

/* STM32F7 I2C Interrupt Clear */
#define STM32F7_I2C_ICR_ARLOCF                  BIT(9)
#define STM32F7_I2C_ICR_BERRCF                  BIT(8)
#define STM32F7_I2C_ICR_STOPCF                  BIT(5)
#define STM32F7_I2C_ICR_NACKCF                  BIT(4)

/* STM32F7 I2C Timing */
#define STM32F7_I2C_TIMINGR_PRESC(n)            (((n) & 0xf) << 28)
#define STM32F7_I2C_TIMINGR_SCLDEL(n)           (((n) & 0xf) << 20)
#define STM32F7_I2C_TIMINGR_SDADEL(n)           (((n) & 0xf) << 16)
#define STM32F7_I2C_TIMINGR_SCLH(n)             (((n) & 0xff) << 8)
#define STM32F7_I2C_TIMINGR_SCLL(n)             ((n) & 0xff)

#define STM32F7_I2C_MAX_LEN                     0xff

#define STM32F7_I2C_DNF_DEFAULT                 0
#define STM32F7_I2C_DNF_MAX                     16

#define STM32F7_I2C_ANALOG_FILTER_ENABLE        1
#define STM32F7_I2C_ANALOG_FILTER_DELAY_MIN     50      /* ns */
#define STM32F7_I2C_ANALOG_FILTER_DELAY_MAX     260     /* ns */

#define STM32F7_I2C_RISE_TIME_DEFAULT           25      /* ns */
#define STM32F7_I2C_FALL_TIME_DEFAULT           10      /* ns */

#define STM32F7_PRESC_MAX                       BIT(4)
#define STM32F7_SCLDEL_MAX                      BIT(4)
#define STM32F7_SDADEL_MAX                      BIT(4)
#define STM32F7_SCLH_MAX                        BIT(8)
#define STM32F7_SCLL_MAX                        BIT(8)

/**
 * struct stm32f7_i2c_spec - private i2c specification timing
 * @rate: I2C bus speed (Hz)
 * @rate_min: 80% of I2C bus speed (Hz)
 * @rate_max: 100% of I2C bus speed (Hz)
 * @fall_max: Max fall time of both SDA and SCL signals (ns)
 * @rise_max: Max rise time of both SDA and SCL signals (ns)
 * @hddat_min: Min data hold time (ns)
 * @vddat_max: Max data valid time (ns)
 * @sudat_min: Min data setup time (ns)
 * @l_min: Min low period of the SCL clock (ns)
 * @h_min: Min high period of the SCL clock (ns)
 */
struct stm32f7_i2c_spec {
        u32 rate;
        u32 rate_min;
        u32 rate_max;
        u32 fall_max;
        u32 rise_max;
        u32 hddat_min;
        u32 vddat_max;
        u32 sudat_min;
        u32 l_min;
        u32 h_min;
};

/**
 * struct stm32f7_i2c_setup - private I2C timing setup parameters
 * @speed: I2C speed mode (standard, Fast Plus)
 * @speed_freq: I2C speed frequency  (Hz)
 * @clock_src: I2C clock source frequency (Hz)
 * @rise_time: Rise time (ns)
 * @fall_time: Fall time (ns)
 * @dnf: Digital filter coefficient (0-16)
 * @analog_filter: Analog filter delay (On/Off)
 */
struct stm32f7_i2c_setup {
        enum stm32_i2c_speed speed;
        u32 speed_freq;
        u32 clock_src;
        u32 rise_time;
        u32 fall_time;
        u8 dnf;
        bool analog_filter;
};

/**
 * struct stm32f7_i2c_timings - private I2C output parameters
 * @prec: Prescaler value
 * @scldel: Data setup time
 * @sdadel: Data hold time
 * @sclh: SCL high period (master mode)
 * @sclh: SCL low period (master mode)
 */
struct stm32f7_i2c_timings {
        struct list_head node;
        u8 presc;
        u8 scldel;
        u8 sdadel;
        u8 sclh;
        u8 scll;
};

/**
 * struct stm32f7_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 stm32f7_i2c_msg {
        u8 addr;
        u32 count;
        u8 *buf;
        int result;
        bool stop;
};

/**
 * struct stm32f7_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, Fast or Fast+
 * @msg: Pointer to data to be written
 * @msg_num: number of I2C messages to be executed
 * @msg_id: message identifiant
 * @f7_msg: customized i2c msg for driver usage
 * @setup: I2C timing input setup
 * @timing: I2C computed timings
 */
struct stm32f7_i2c_dev {
        struct i2c_adapter adap;
        struct device *dev;
        void __iomem *base;
        struct completion complete;
        struct clk *clk;
        int speed;
        struct i2c_msg *msg;
        unsigned int msg_num;
        unsigned int msg_id;
        struct stm32f7_i2c_msg f7_msg;
        struct stm32f7_i2c_setup setup;
        struct stm32f7_i2c_timings timing;
};

/**
 * All these values are coming from I2C Specification, Version 6.0, 4th of
 * April 2014.
 *
 * Table10. Characteristics of the SDA and SCL bus lines for Standard, Fast,
 * and Fast-mode Plus I2C-bus devices
 */
static struct stm32f7_i2c_spec i2c_specs[] = {
        [STM32_I2C_SPEED_STANDARD] = {
                .rate = 100000,
                .rate_min = 80000,
                .rate_max = 100000,
                .fall_max = 300,
                .rise_max = 1000,
                .hddat_min = 0,
                .vddat_max = 3450,
                .sudat_min = 250,
                .l_min = 4700,
                .h_min = 4000,
        },
        [STM32_I2C_SPEED_FAST] = {
                .rate = 400000,
                .rate_min = 320000,
                .rate_max = 400000,
                .fall_max = 300,
                .rise_max = 300,
                .hddat_min = 0,
                .vddat_max = 900,
                .sudat_min = 100,
                .l_min = 1300,
                .h_min = 600,
        },
        [STM32_I2C_SPEED_FAST_PLUS] = {
                .rate = 1000000,
                .rate_min = 800000,
                .rate_max = 1000000,
                .fall_max = 100,
                .rise_max = 120,
                .hddat_min = 0,
                .vddat_max = 450,
                .sudat_min = 50,
                .l_min = 500,
                .h_min = 260,
        },
};

static const struct stm32f7_i2c_setup stm32f7_setup = {
        .rise_time = STM32F7_I2C_RISE_TIME_DEFAULT,
        .fall_time = STM32F7_I2C_FALL_TIME_DEFAULT,
        .dnf = STM32F7_I2C_DNF_DEFAULT,
        .analog_filter = STM32F7_I2C_ANALOG_FILTER_ENABLE,
};

static inline void stm32f7_i2c_set_bits(void __iomem *reg, u32 mask)
{
        writel_relaxed(readl_relaxed(reg) | mask, reg);
}

static inline void stm32f7_i2c_clr_bits(void __iomem *reg, u32 mask)
{
        writel_relaxed(readl_relaxed(reg) & ~mask, reg);
}

static int stm32f7_i2c_compute_timing(struct stm32f7_i2c_dev *i2c_dev,
                                      struct stm32f7_i2c_setup *setup,
                                      struct stm32f7_i2c_timings *output)
{
        u32 p_prev = STM32F7_PRESC_MAX;
        u32 i2cclk = DIV_ROUND_CLOSEST(NSEC_PER_SEC,
                                       setup->clock_src);
        u32 i2cbus = DIV_ROUND_CLOSEST(NSEC_PER_SEC,
                                       setup->speed_freq);
        u32 clk_error_prev = i2cbus;
        u32 tsync;
        u32 af_delay_min, af_delay_max;
        u32 dnf_delay;
        u32 clk_min, clk_max;
        int sdadel_min, sdadel_max;
        int scldel_min;
        struct stm32f7_i2c_timings *v, *_v, *s;
        struct list_head solutions;
        u16 p, l, a, h;
        int ret = 0;

        if (setup->speed >= STM32_I2C_SPEED_END) {
                dev_err(i2c_dev->dev, "speed out of bound {%d/%d}\n",
                        setup->speed, STM32_I2C_SPEED_END - 1);
                return -EINVAL;
        }

        if ((setup->rise_time > i2c_specs[setup->speed].rise_max) ||
            (setup->fall_time > i2c_specs[setup->speed].fall_max)) {
                dev_err(i2c_dev->dev,
                        "timings out of bound Rise{%d>%d}/Fall{%d>%d}\n",
                        setup->rise_time, i2c_specs[setup->speed].rise_max,
                        setup->fall_time, i2c_specs[setup->speed].fall_max);
                return -EINVAL;
        }

        if (setup->dnf > STM32F7_I2C_DNF_MAX) {
                dev_err(i2c_dev->dev,
                        "DNF out of bound %d/%d\n",
                        setup->dnf, STM32F7_I2C_DNF_MAX);
                return -EINVAL;
        }

        if (setup->speed_freq > i2c_specs[setup->speed].rate) {
                dev_err(i2c_dev->dev, "ERROR: Freq {%d/%d}\n",
                        setup->speed_freq, i2c_specs[setup->speed].rate);
                return -EINVAL;
        }

        /*  Analog and Digital Filters */
        af_delay_min =
                (setup->analog_filter ?
                 STM32F7_I2C_ANALOG_FILTER_DELAY_MIN : 0);
        af_delay_max =
                (setup->analog_filter ?
                 STM32F7_I2C_ANALOG_FILTER_DELAY_MAX : 0);
        dnf_delay = setup->dnf * i2cclk;

        sdadel_min = setup->fall_time - i2c_specs[setup->speed].hddat_min -
                af_delay_min - (setup->dnf + 3) * i2cclk;

        sdadel_max = i2c_specs[setup->speed].vddat_max - setup->rise_time -
                af_delay_max - (setup->dnf + 4) * i2cclk;

        scldel_min = setup->rise_time + i2c_specs[setup->speed].sudat_min;

        if (sdadel_min < 0)
                sdadel_min = 0;
        if (sdadel_max < 0)
                sdadel_max = 0;

        dev_dbg(i2c_dev->dev, "SDADEL(min/max): %i/%i, SCLDEL(Min): %i\n",
                sdadel_min, sdadel_max, scldel_min);

        INIT_LIST_HEAD(&solutions);
        /* Compute possible values for PRESC, SCLDEL and SDADEL */
        for (p = 0; p < STM32F7_PRESC_MAX; p++) {
                for (l = 0; l < STM32F7_SCLDEL_MAX; l++) {
                        u32 scldel = (l + 1) * (p + 1) * i2cclk;

                        if (scldel < scldel_min)
                                continue;

                        for (a = 0; a < STM32F7_SDADEL_MAX; a++) {
                                u32 sdadel = (a * (p + 1) + 1) * i2cclk;

                                if (((sdadel >= sdadel_min) &&
                                     (sdadel <= sdadel_max)) &&
                                    (p != p_prev)) {
                                        v = kmalloc(sizeof(*v), GFP_KERNEL);
                                        if (!v) {
                                                ret = -ENOMEM;
                                                goto exit;
                                        }

                                        v->presc = p;
                                        v->scldel = l;
                                        v->sdadel = a;
                                        p_prev = p;

                                        list_add_tail(&v->node,
                                                      &solutions);
                                }
                        }
                }
        }

        if (list_empty(&solutions)) {
                dev_err(i2c_dev->dev, "no Prescaler solution\n");
                ret = -EPERM;
                goto exit;
        }

        tsync = af_delay_min + dnf_delay + (2 * i2cclk);
        s = NULL;
        clk_max = NSEC_PER_SEC / i2c_specs[setup->speed].rate_min;
        clk_min = NSEC_PER_SEC / i2c_specs[setup->speed].rate_max;

        /*
         * Among Prescaler possibilities discovered above figures out SCL Low
         * and High Period. Provided:
         * - SCL Low Period has to be higher than SCL Clock Low Period
         *   defined by I2C Specification. I2C Clock has to be lower than
         *   (SCL Low Period - Analog/Digital filters) / 4.
         * - SCL High Period has to be lower than SCL Clock High Period
         *   defined by I2C Specification
         * - I2C Clock has to be lower than SCL High Period
         */
        list_for_each_entry(v, &solutions, node) {
                u32 prescaler = (v->presc + 1) * i2cclk;

                for (l = 0; l < STM32F7_SCLL_MAX; l++) {
                        u32 tscl_l = (l + 1) * prescaler + tsync;

                        if ((tscl_l < i2c_specs[setup->speed].l_min) ||
                            (i2cclk >=
                             ((tscl_l - af_delay_min - dnf_delay) / 4))) {
                                continue;
                        }

                        for (h = 0; h < STM32F7_SCLH_MAX; h++) {
                                u32 tscl_h = (h + 1) * prescaler + tsync;
                                u32 tscl = tscl_l + tscl_h +
                                        setup->rise_time + setup->fall_time;

                                if ((tscl >= clk_min) && (tscl <= clk_max) &&
                                    (tscl_h >= i2c_specs[setup->speed].h_min) &&
                                    (i2cclk < tscl_h)) {
                                        int clk_error = tscl - i2cbus;

                                        if (clk_error < 0)
                                                clk_error = -clk_error;

                                        if (clk_error < clk_error_prev) {
                                                clk_error_prev = clk_error;
                                                v->scll = l;
                                                v->sclh = h;
                                                s = v;
                                        }
                                }
                        }
                }
        }

        if (!s) {
                dev_err(i2c_dev->dev, "no solution at all\n");
                ret = -EPERM;
                goto exit;
        }

        output->presc = s->presc;
        output->scldel = s->scldel;
        output->sdadel = s->sdadel;
        output->scll = s->scll;
        output->sclh = s->sclh;

        dev_dbg(i2c_dev->dev,
                "Presc: %i, scldel: %i, sdadel: %i, scll: %i, sclh: %i\n",
                output->presc,
                output->scldel, output->sdadel,
                output->scll, output->sclh);

exit:
        /* Release list and memory */
        list_for_each_entry_safe(v, _v, &solutions, node) {
                list_del(&v->node);
                kfree(v);
        }

        return ret;
}

static int stm32f7_i2c_setup_timing(struct stm32f7_i2c_dev *i2c_dev,
                                    struct stm32f7_i2c_setup *setup)
{
        int ret = 0;

        setup->speed = i2c_dev->speed;
        setup->speed_freq = i2c_specs[setup->speed].rate;
        setup->clock_src = clk_get_rate(i2c_dev->clk);

        if (!setup->clock_src) {
                dev_err(i2c_dev->dev, "clock rate is 0\n");
                return -EINVAL;
        }

        do {
                ret = stm32f7_i2c_compute_timing(i2c_dev, setup,
                                                 &i2c_dev->timing);
                if (ret) {
                        dev_err(i2c_dev->dev,
                                "failed to compute I2C timings.\n");
                        if (i2c_dev->speed > STM32_I2C_SPEED_STANDARD) {
                                i2c_dev->speed--;
                                setup->speed = i2c_dev->speed;
                                setup->speed_freq =
                                        i2c_specs[setup->speed].rate;
                                dev_warn(i2c_dev->dev,
                                         "downgrade I2C Speed Freq to (%i)\n",
                                         i2c_specs[setup->speed].rate);
                        } else {
                                break;
                        }
                }
        } while (ret);

        if (ret) {
                dev_err(i2c_dev->dev, "Impossible to compute I2C timings.\n");
                return ret;
        }

        dev_dbg(i2c_dev->dev, "I2C Speed(%i), Freq(%i), Clk Source(%i)\n",
                setup->speed, setup->speed_freq, setup->clock_src);
        dev_dbg(i2c_dev->dev, "I2C Rise(%i) and Fall(%i) Time\n",
                setup->rise_time, setup->fall_time);
        dev_dbg(i2c_dev->dev, "I2C Analog Filter(%s), DNF(%i)\n",
                (setup->analog_filter ? "On" : "Off"), setup->dnf);

        return 0;
}

static void stm32f7_i2c_hw_config(struct stm32f7_i2c_dev *i2c_dev)
{
        struct stm32f7_i2c_timings *t = &i2c_dev->timing;
        u32 timing = 0;

        /* Timing settings */
        timing |= STM32F7_I2C_TIMINGR_PRESC(t->presc);
        timing |= STM32F7_I2C_TIMINGR_SCLDEL(t->scldel);
        timing |= STM32F7_I2C_TIMINGR_SDADEL(t->sdadel);
        timing |= STM32F7_I2C_TIMINGR_SCLH(t->sclh);
        timing |= STM32F7_I2C_TIMINGR_SCLL(t->scll);
        writel_relaxed(timing, i2c_dev->base + STM32F7_I2C_TIMINGR);

        /* Enable I2C */
        if (i2c_dev->setup.analog_filter)
                stm32f7_i2c_clr_bits(i2c_dev->base + STM32F7_I2C_CR1,
                                     STM32F7_I2C_CR1_ANFOFF);
        else
                stm32f7_i2c_set_bits(i2c_dev->base + STM32F7_I2C_CR1,
                                     STM32F7_I2C_CR1_ANFOFF);
        stm32f7_i2c_set_bits(i2c_dev->base + STM32F7_I2C_CR1,
                             STM32F7_I2C_CR1_PE);
}

static void stm32f7_i2c_write_tx_data(struct stm32f7_i2c_dev *i2c_dev)
{
        struct stm32f7_i2c_msg *f7_msg = &i2c_dev->f7_msg;
        void __iomem *base = i2c_dev->base;

        if (f7_msg->count) {
                writeb_relaxed(*f7_msg->buf++, base + STM32F7_I2C_TXDR);
                f7_msg->count--;
        }
}

static void stm32f7_i2c_read_rx_data(struct stm32f7_i2c_dev *i2c_dev)
{
        struct stm32f7_i2c_msg *f7_msg = &i2c_dev->f7_msg;
        void __iomem *base = i2c_dev->base;

        if (f7_msg->count) {
                *f7_msg->buf++ = readb_relaxed(base + STM32F7_I2C_RXDR);
                f7_msg->count--;
        }
}

static void stm32f7_i2c_reload(struct stm32f7_i2c_dev *i2c_dev)
{
        struct stm32f7_i2c_msg *f7_msg = &i2c_dev->f7_msg;
        u32 cr2;

        cr2 = readl_relaxed(i2c_dev->base + STM32F7_I2C_CR2);

        cr2 &= ~STM32F7_I2C_CR2_NBYTES_MASK;
        if (f7_msg->count > STM32F7_I2C_MAX_LEN) {
                cr2 |= STM32F7_I2C_CR2_NBYTES(STM32F7_I2C_MAX_LEN);
        } else {
                cr2 &= ~STM32F7_I2C_CR2_RELOAD;
                cr2 |= STM32F7_I2C_CR2_NBYTES(f7_msg->count);
        }

        writel_relaxed(cr2, i2c_dev->base + STM32F7_I2C_CR2);
}

static int stm32f7_i2c_wait_free_bus(struct stm32f7_i2c_dev *i2c_dev)
{
        u32 status;
        int ret;

        ret = readl_relaxed_poll_timeout(i2c_dev->base + STM32F7_I2C_ISR,
                                         status,
                                         !(status & STM32F7_I2C_ISR_BUSY),
                                         10, 1000);
        if (ret) {
                dev_dbg(i2c_dev->dev, "bus busy\n");
                ret = -EBUSY;
        }

        return ret;
}

static void stm32f7_i2c_xfer_msg(struct stm32f7_i2c_dev *i2c_dev,
                                 struct i2c_msg *msg)
{
        struct stm32f7_i2c_msg *f7_msg = &i2c_dev->f7_msg;
        void __iomem *base = i2c_dev->base;
        u32 cr1, cr2;

        f7_msg->addr = msg->addr;
        f7_msg->buf = msg->buf;
        f7_msg->count = msg->len;
        f7_msg->result = 0;
        f7_msg->stop = (i2c_dev->msg_id >= i2c_dev->msg_num - 1);

        reinit_completion(&i2c_dev->complete);

        cr1 = readl_relaxed(base + STM32F7_I2C_CR1);
        cr2 = readl_relaxed(base + STM32F7_I2C_CR2);

        /* Set transfer direction */
        cr2 &= ~STM32F7_I2C_CR2_RD_WRN;
        if (msg->flags & I2C_M_RD)
                cr2 |= STM32F7_I2C_CR2_RD_WRN;

        /* Set slave address */
        cr2 &= ~STM32F7_I2C_CR2_SADD7_MASK;
        cr2 |= STM32F7_I2C_CR2_SADD7(f7_msg->addr);

        /* Set nb bytes to transfer and reload if needed */
        cr2 &= ~(STM32F7_I2C_CR2_NBYTES_MASK | STM32F7_I2C_CR2_RELOAD);
        if (f7_msg->count > STM32F7_I2C_MAX_LEN) {
                cr2 |= STM32F7_I2C_CR2_NBYTES(STM32F7_I2C_MAX_LEN);
                cr2 |= STM32F7_I2C_CR2_RELOAD;
        } else {
                cr2 |= STM32F7_I2C_CR2_NBYTES(f7_msg->count);
        }

        /* Enable NACK, STOP, error and transfer complete interrupts */
        cr1 |= STM32F7_I2C_CR1_ERRIE | STM32F7_I2C_CR1_TCIE |
                STM32F7_I2C_CR1_STOPIE | STM32F7_I2C_CR1_NACKIE;

        /* Clear TX/RX interrupt */
        cr1 &= ~(STM32F7_I2C_CR1_RXIE | STM32F7_I2C_CR1_TXIE);

        /* Enable RX/TX interrupt according to msg direction */
        if (msg->flags & I2C_M_RD)
                cr1 |= STM32F7_I2C_CR1_RXIE;
        else
                cr1 |= STM32F7_I2C_CR1_TXIE;

        /* Configure Start/Repeated Start */
        cr2 |= STM32F7_I2C_CR2_START;

        /* Write configurations registers */
        writel_relaxed(cr1, base + STM32F7_I2C_CR1);
        writel_relaxed(cr2, base + STM32F7_I2C_CR2);
}

static void stm32f7_i2c_disable_irq(struct stm32f7_i2c_dev *i2c_dev, u32 mask)
{
        stm32f7_i2c_clr_bits(i2c_dev->base + STM32F7_I2C_CR1, mask);
}

static irqreturn_t stm32f7_i2c_isr_event(int irq, void *data)
{
        struct stm32f7_i2c_dev *i2c_dev = data;
        struct stm32f7_i2c_msg *f7_msg = &i2c_dev->f7_msg;
        void __iomem *base = i2c_dev->base;
        u32 status, mask;

        status = readl_relaxed(i2c_dev->base + STM32F7_I2C_ISR);

        /* Tx empty */
        if (status & STM32F7_I2C_ISR_TXIS)
                stm32f7_i2c_write_tx_data(i2c_dev);

        /* RX not empty */
        if (status & STM32F7_I2C_ISR_RXNE)
                stm32f7_i2c_read_rx_data(i2c_dev);

        /* NACK received */
        if (status & STM32F7_I2C_ISR_NACKF) {
                dev_dbg(i2c_dev->dev, "<%s>: Receive NACK\n", __func__);
                writel_relaxed(STM32F7_I2C_ICR_NACKCF, base + STM32F7_I2C_ICR);
                f7_msg->result = -ENXIO;
        }

        /* STOP detection flag */
        if (status & STM32F7_I2C_ISR_STOPF) {
                /* Disable interrupts */
                stm32f7_i2c_disable_irq(i2c_dev, STM32F7_I2C_ALL_IRQ_MASK);

                /* Clear STOP flag */
                writel_relaxed(STM32F7_I2C_ICR_STOPCF, base + STM32F7_I2C_ICR);

                complete(&i2c_dev->complete);
        }

        /* Transfer complete */
        if (status & STM32F7_I2C_ISR_TC) {
                if (f7_msg->stop) {
                        mask = STM32F7_I2C_CR2_STOP;
                        stm32f7_i2c_set_bits(base + STM32F7_I2C_CR2, mask);
                } else {
                        i2c_dev->msg_id++;
                        i2c_dev->msg++;
                        stm32f7_i2c_xfer_msg(i2c_dev, i2c_dev->msg);
                }
        }

        /*
         * Transfer Complete Reload: 255 data bytes have been transferred
         * We have to prepare the I2C controller to transfer the remaining
         * data.
         */
        if (status & STM32F7_I2C_ISR_TCR)
                stm32f7_i2c_reload(i2c_dev);

        return IRQ_HANDLED;
}

static irqreturn_t stm32f7_i2c_isr_error(int irq, void *data)
{
        struct stm32f7_i2c_dev *i2c_dev = data;
        struct stm32f7_i2c_msg *f7_msg = &i2c_dev->f7_msg;
        void __iomem *base = i2c_dev->base;
        struct device *dev = i2c_dev->dev;
        u32 status;

        status = readl_relaxed(i2c_dev->base + STM32F7_I2C_ISR);

        /* Bus error */
        if (status & STM32F7_I2C_ISR_BERR) {
                dev_err(dev, "<%s>: Bus error\n", __func__);
                writel_relaxed(STM32F7_I2C_ICR_BERRCF, base + STM32F7_I2C_ICR);
                f7_msg->result = -EIO;
        }

        /* Arbitration loss */
        if (status & STM32F7_I2C_ISR_ARLO) {
                dev_dbg(dev, "<%s>: Arbitration loss\n", __func__);
                writel_relaxed(STM32F7_I2C_ICR_ARLOCF, base + STM32F7_I2C_ICR);
                f7_msg->result = -EAGAIN;
        }

        stm32f7_i2c_disable_irq(i2c_dev, STM32F7_I2C_ALL_IRQ_MASK);

        complete(&i2c_dev->complete);

        return IRQ_HANDLED;
}

static int stm32f7_i2c_xfer(struct i2c_adapter *i2c_adap,
                            struct i2c_msg msgs[], int num)
{
        struct stm32f7_i2c_dev *i2c_dev = i2c_get_adapdata(i2c_adap);
        struct stm32f7_i2c_msg *f7_msg = &i2c_dev->f7_msg;
        unsigned long time_left;
        int ret;

        i2c_dev->msg = msgs;
        i2c_dev->msg_num = num;
        i2c_dev->msg_id = 0;

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

        ret = stm32f7_i2c_wait_free_bus(i2c_dev);
        if (ret)
                goto clk_free;

        stm32f7_i2c_xfer_msg(i2c_dev, msgs);

        time_left = wait_for_completion_timeout(&i2c_dev->complete,
                                                i2c_dev->adap.timeout);
        ret = f7_msg->result;

        if (!time_left) {
                dev_dbg(i2c_dev->dev, "Access to slave 0x%x timed out\n",
                        i2c_dev->msg->addr);
                ret = -ETIMEDOUT;
        }

clk_free:
        clk_disable(i2c_dev->clk);

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

static u32 stm32f7_i2c_func(struct i2c_adapter *adap)
{
        return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
}

static struct i2c_algorithm stm32f7_i2c_algo = {
        .master_xfer = stm32f7_i2c_xfer,
        .functionality = stm32f7_i2c_func,
};

static int stm32f7_i2c_probe(struct platform_device *pdev)
{
        struct device_node *np = pdev->dev.of_node;
        struct stm32f7_i2c_dev *i2c_dev;
        const struct stm32f7_i2c_setup *setup;
        struct resource *res;
        u32 irq_error, irq_event, clk_rate, rise_time, fall_time;
        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(&pdev->dev, "Failed to prepare_enable clock\n");
                return ret;
        }

        i2c_dev->speed = STM32_I2C_SPEED_STANDARD;
        ret = device_property_read_u32(&pdev->dev, "clock-frequency",
                                       &clk_rate);
        if (!ret && clk_rate >= 1000000)
                i2c_dev->speed = STM32_I2C_SPEED_FAST_PLUS;
        else if (!ret && clk_rate >= 400000)
                i2c_dev->speed = STM32_I2C_SPEED_FAST;
        else if (!ret && clk_rate >= 100000)
                i2c_dev->speed = STM32_I2C_SPEED_STANDARD;

        rst = devm_reset_control_get(&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->dev = &pdev->dev;

        ret = devm_request_irq(&pdev->dev, irq_event, stm32f7_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, stm32f7_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;
        }

        setup = of_device_get_match_data(&pdev->dev);
        i2c_dev->setup = *setup;

        ret = device_property_read_u32(i2c_dev->dev, "i2c-scl-rising-time-ns",
                                       &rise_time);
        if (!ret)
                i2c_dev->setup.rise_time = rise_time;

        ret = device_property_read_u32(i2c_dev->dev, "i2c-scl-falling-time-ns",
                                       &fall_time);
        if (!ret)
                i2c_dev->setup.fall_time = fall_time;

        ret = stm32f7_i2c_setup_timing(i2c_dev, &i2c_dev->setup);
        if (ret)
                goto clk_free;

        stm32f7_i2c_hw_config(i2c_dev);

        adap = &i2c_dev->adap;
        i2c_set_adapdata(adap, i2c_dev);
        snprintf(adap->name, sizeof(adap->name), "STM32F7 I2C(%pa)",
                 &res->start);
        adap->owner = THIS_MODULE;
        adap->timeout = 2 * HZ;
        adap->retries = 3;
        adap->algo = &stm32f7_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, "STM32F7 I2C-%d bus adapter\n", adap->nr);

        return 0;

clk_free:
        clk_disable_unprepare(i2c_dev->clk);

        return ret;
}

static int stm32f7_i2c_remove(struct platform_device *pdev)
{
        struct stm32f7_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 stm32f7_i2c_match[] = {
        { .compatible = "st,stm32f7-i2c", .data = &stm32f7_setup},
        {},
};
MODULE_DEVICE_TABLE(of, stm32f7_i2c_match);

static struct platform_driver stm32f7_i2c_driver = {
        .driver = {
                .name = "stm32f7-i2c",
                .of_match_table = stm32f7_i2c_match,
        },
        .probe = stm32f7_i2c_probe,
        .remove = stm32f7_i2c_remove,
};

module_platform_driver(stm32f7_i2c_driver);

MODULE_AUTHOR("M'boumba Cedric Madianga <cedric.madianga@gmail.com>");
MODULE_DESCRIPTION("STMicroelectronics STM32F7 I2C driver");
MODULE_LICENSE("GPL v2");