/*
 * 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_DNF_MASK		GENMASK(11, 8)
#define STM32F7_I2C_CR1_DNF(n)			(((n) & 0xf) << 8)
#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			15

#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 = i2c_specs[setup->speed].hddat_min + setup->fall_time -
		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);

	/* Program the Digital Filter */
	stm32f7_i2c_clr_bits(i2c_dev->base + STM32F7_I2C_CR1,
			     STM32F7_I2C_CR1_DNF_MASK);
	stm32f7_i2c_set_bits(i2c_dev->base + STM32F7_I2C_CR1,
			     STM32F7_I2C_CR1_DNF(i2c_dev->setup.dnf));

	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);
	if (!setup) {
		dev_err(&pdev->dev, "Can't get device data\n");
		ret = -ENODEV;
		goto clk_free;
	}
	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");