[PATCH 2/5] i2c: Add STM32F4 I2C driver

["M'boumba Cedric Madianga" <cedric.madianga@gmail.com>]

This patch adds support for the STM32F4 I2C controller.

Signed-off-by: M'boumba Cedric Madianga <cedric.madianga@gmail.com>
---
 drivers/i2c/busses/Kconfig       |  10 +
 drivers/i2c/busses/Makefile      |   1 +
 drivers/i2c/busses/i2c-stm32f4.c | 872 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 883 insertions(+)
 create mode 100644 drivers/i2c/busses/i2c-stm32f4.c

diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index 2dd40dd..947894a 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -873,6 +873,16 @@ config I2C_ST
 	  This driver can also be built as module. If so, the module
 	  will be called i2c-st.
 
+config I2C_STM32F4
+	tristate "STMicroelectronics STM32F4 I2C support"
+	depends on ARCH_STM32
+	help
+	  Enable this option to add support for STM32 I2C controller embedded
+	  in STM32F4 SoCs.
+
+	  This driver can also be built as module. If so, the module
+	  will be called i2c-stm32f4.
+
 config I2C_STU300
 	tristate "ST Microelectronics DDC I2C interface"
 	depends on MACH_U300
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index 37f2819..2ac0eb2 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -84,6 +84,7 @@ obj-$(CONFIG_I2C_SH_MOBILE)	+= i2c-sh_mobile.o
 obj-$(CONFIG_I2C_SIMTEC)	+= i2c-simtec.o
 obj-$(CONFIG_I2C_SIRF)		+= i2c-sirf.o
 obj-$(CONFIG_I2C_ST)		+= i2c-st.o
+obj-$(CONFIG_I2C_STM32F4)	+= i2c-stm32f4.o
 obj-$(CONFIG_I2C_STU300)	+= i2c-stu300.o
 obj-$(CONFIG_I2C_SUN6I_P2WI)	+= i2c-sun6i-p2wi.o
 obj-$(CONFIG_I2C_TEGRA)		+= i2c-tegra.o
diff --git a/drivers/i2c/busses/i2c-stm32f4.c b/drivers/i2c/busses/i2c-stm32f4.c
new file mode 100644
index 0000000..4692213
--- /dev/null
+++ b/drivers/i2c/busses/i2c-stm32f4.c
@@ -0,0 +1,872 @@
+/*
+ * Driver for STMicroelectronics STM32 I2C controller
+ *
+ * Copyright (C) M'boumba Cedric Madianga 2015
+ * Author: M'boumba Cedric Madianga <cedric.madianga@gmail.com>
+ *
+ * This driver is based on st-i2c.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>
+
+/* 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_SWRST		BIT(15)
+#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_TRISE_MASK	GENMASK(5, 0)
+#define STM32F4_I2C_TRISE_TRISE(n)	((n & STM32F4_I2C_TRISE_TRISE_MASK))
+
+/* STM32F4 I2C Filter */
+#define STM32F4_I2C_FLTR_DNF_MASK	GENMASK(3, 0)
+#define STM32F4_I2C_FLTR_DNF(n)		((n & STM32F4_I2C_FLTR_DNF_MASK))
+#define STM32F4_I2C_FLTR_ANOFF		BIT(4)
+
+#define STM32F4_I2C_MAX_FREQ		0x2a
+#define STM32F4_I2C_MIN_CCR		0x4
+
+enum stm32f4_i2c_speed {
+	STM32F4_I2C_SPEED_STANDARD, /* 100 kHz */
+	STM32F4_I2C_SPEED_FAST, /* 400 kHz */
+	STM32F4_I2C_SPEED_END,
+};
+
+/**
+ * struct stm32f4_i2c_timings - per-Mode tuning parameters
+ * @rate: I2C bus rate
+ * @duty: Fast mode duty cycle
+ */
+struct stm32f4_i2c_timings {
+	u32 rate;
+	u32 duty;
+};
+
+/**
+ * struct stm32f4_i2c_client - 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_client {
+	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
+ * @irq_event: interrupt event line for the controller
+ * @irq_error: interrupt error line for the controller
+ * @clk: hw i2c clock
+ * speed: I2C clock frequency of the controller. Standard or Fast only supported
+ * @client: I2C transfer information
+ * @busy: I2C transfer on-going
+ * @rst: I2C reset line
+ */
+struct stm32f4_i2c_dev {
+	struct i2c_adapter		adap;
+	struct device			*dev;
+	void __iomem			*base;
+	struct completion		complete;
+	int				irq_event;
+	int				irq_error;
+	struct clk			*clk;
+	int				speed;
+	struct stm32f4_i2c_client	client;
+	bool				busy;
+	struct reset_control		*rst;
+};
+
+static struct stm32f4_i2c_timings i2c_timings[] = {
+	[STM32F4_I2C_SPEED_STANDARD] = {
+		.rate			= 100000,
+		.duty			= 0,
+	},
+	[STM32F4_I2C_SPEED_FAST] = {
+		.rate			= 400000,
+		.duty			= 0,
+	},
+};
+
+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_soft_reset(struct stm32f4_i2c_dev *i2c_dev)
+{
+	void __iomem *reg = i2c_dev->base + STM32F4_I2C_CR1;
+
+	stm32f4_i2c_set_bits(reg, STM32F4_I2C_CR1_SWRST);
+	stm32f4_i2c_clr_bits(reg, STM32F4_I2C_CR1_SWRST);
+}
+
+static void stm32f4_i2c_set_periph_clk_freq(struct stm32f4_i2c_dev *i2c_dev)
+{
+	u32 clk_rate, cr2, freq;
+
+	cr2 = readl_relaxed(i2c_dev->base + STM32F4_I2C_CR2);
+	cr2 &= ~STM32F4_I2C_CR2_FREQ_MASK;
+
+	clk_rate = clk_get_rate(i2c_dev->clk);
+
+	freq = clk_rate / 1000000;
+	if (freq > STM32F4_I2C_MAX_FREQ)
+		freq = STM32F4_I2C_MAX_FREQ;
+
+	cr2 |= STM32F4_I2C_CR2_FREQ(freq);
+	writel_relaxed(cr2, i2c_dev->base + STM32F4_I2C_CR2);
+}
+
+static void stm32f4_i2c_set_rise_time(struct stm32f4_i2c_dev *i2c_dev)
+{
+	u32 trise, freq, cr2;
+
+	cr2 = readl_relaxed(i2c_dev->base + STM32F4_I2C_CR2);
+	freq = cr2 & STM32F4_I2C_CR2_FREQ_MASK;
+
+	trise = readl_relaxed(i2c_dev->base + STM32F4_I2C_TRISE);
+	trise &= ~STM32F4_I2C_TRISE_TRISE_MASK;
+
+	if (i2c_dev->speed == STM32F4_I2C_SPEED_STANDARD)
+		trise |= STM32F4_I2C_TRISE_TRISE((freq + 1));
+	else
+		trise |= STM32F4_I2C_TRISE_TRISE((((freq * 300) / 1000) + 1));
+
+	writel_relaxed(trise, i2c_dev->base + STM32F4_I2C_TRISE);
+}
+
+static void stm32f4_i2c_set_speed_mode(struct stm32f4_i2c_dev *i2c_dev)
+{
+	struct stm32f4_i2c_timings *t = &i2c_timings[i2c_dev->speed];
+	u32 ccr, val, clk_rate;
+
+	ccr = readl_relaxed(i2c_dev->base + STM32F4_I2C_CCR);
+	ccr &= ~(STM32F4_I2C_CCR_FS | STM32F4_I2C_CCR_DUTY |
+		 STM32F4_I2C_CCR_CCR_MASK);
+
+	clk_rate = clk_get_rate(i2c_dev->clk);
+
+	switch (i2c_dev->speed) {
+	case STM32F4_I2C_SPEED_STANDARD:
+		val = clk_rate / t->rate * 2;
+		if (val < STM32F4_I2C_MIN_CCR)
+			ccr |= STM32F4_I2C_CCR_CCR(STM32F4_I2C_MIN_CCR);
+		else
+			ccr |= STM32F4_I2C_CCR_CCR(val);
+		break;
+	case STM32F4_I2C_SPEED_FAST:
+		ccr |= STM32F4_I2C_CCR_FS;
+		if (t->duty) {
+			ccr |= STM32F4_I2C_CCR_DUTY;
+			ccr |= STM32F4_I2C_CCR_CCR(clk_rate / t->rate * 25);
+		} else {
+			ccr |= STM32F4_I2C_CCR_CCR(clk_rate / t->rate * 3);
+		}
+		break;
+	default:
+		dev_err(i2c_dev->dev, "I2C speed mode not supported\n");
+	}
+
+	writel_relaxed(ccr, i2c_dev->base + STM32F4_I2C_CCR);
+}
+
+static void stm32f4_i2c_set_filter(struct stm32f4_i2c_dev *i2c_dev)
+{
+	u32 filter;
+
+	/* Enable analog noise filter and disable digital noise filter */
+	filter = readl_relaxed(i2c_dev->base + STM32F4_I2C_FLTR);
+	filter &= ~(STM32F4_I2C_FLTR_ANOFF | STM32F4_I2C_FLTR_DNF_MASK);
+	writel_relaxed(filter, i2c_dev->base + STM32F4_I2C_FLTR);
+}
+
+/**
+ * stm32f4_i2c_hw_config() - Prepare I2C block
+ * @i2c_dev: Controller's private data
+ */
+static void stm32f4_i2c_hw_config(struct stm32f4_i2c_dev *i2c_dev)
+{
+	void __iomem *reg = i2c_dev->base + STM32F4_I2C_CR1;
+
+	/* Disable I2C */
+	stm32f4_i2c_clr_bits(reg, STM32F4_I2C_CR1_PE);
+
+	stm32f4_i2c_set_periph_clk_freq(i2c_dev);
+
+	stm32f4_i2c_set_rise_time(i2c_dev);
+
+	stm32f4_i2c_set_speed_mode(i2c_dev);
+
+	stm32f4_i2c_set_filter(i2c_dev);
+
+	/* Enable I2C */
+	stm32f4_i2c_set_bits(reg, STM32F4_I2C_CR1_PE);
+}
+
+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_err(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_client *c = &i2c_dev->client;
+
+	stm32f4_i2c_write_byte(i2c_dev, *c->buf++);
+	c->count--;
+}
+
+static void stm32f4_i2c_read_msg(struct stm32f4_i2c_dev *i2c_dev)
+{
+	struct stm32f4_i2c_client *c = &i2c_dev->client;
+	u32 rbuf;
+
+	rbuf = readl_relaxed(i2c_dev->base + STM32F4_I2C_DR);
+	*c->buf++ = (u8)rbuf & 0xff;
+	c->count--;
+}
+
+static void stm32f4_i2c_terminate_xfer(struct stm32f4_i2c_dev *i2c_dev)
+{
+	struct stm32f4_i2c_client *c = &i2c_dev->client;
+	void __iomem *reg = i2c_dev->base + STM32F4_I2C_CR2;
+
+	/* Disable all interrupts */
+	stm32f4_i2c_clr_bits(reg, STM32F4_I2C_CR2_IRQ_MASK);
+
+	/* Set STOP or REPSTART */
+	reg = i2c_dev->base + STM32F4_I2C_CR1;
+	if (c->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_client *c = &i2c_dev->client;
+	void __iomem *reg = i2c_dev->base + STM32F4_I2C_CR2;
+
+	if (c->count) {
+		stm32f4_i2c_write_msg(i2c_dev);
+		if (!c->count) {
+			/* Disable BUF interrupt */
+			stm32f4_i2c_clr_bits(reg, STM32F4_I2C_CR2_ITBUFEN);
+		}
+	} else {
+		stm32f4_i2c_terminate_xfer(i2c_dev);
+	}
+}
+
+/**
+ * stm32f4_i2c_handle_tx_btf() - Handle byte transfer finished interrupt
+ * in case of write
+ * @i2c_dev: Controller's private data
+ */
+static void stm32f4_i2c_handle_tx_btf(struct stm32f4_i2c_dev *i2c_dev)
+{
+	struct stm32f4_i2c_client *c = &i2c_dev->client;
+
+	if (c->count)
+		stm32f4_i2c_write_msg(i2c_dev);
+	else
+		stm32f4_i2c_terminate_xfer(i2c_dev);
+}
+
+/**
+ * stm32f4_i2c_handle_read() - Handle FIFO enmpty interrupt in case of read
+ * @i2c_dev: Controller's private data
+ */
+static void stm32f4_i2c_handle_read(struct stm32f4_i2c_dev *i2c_dev)
+{
+	struct stm32f4_i2c_client *c = &i2c_dev->client;
+	void __iomem *reg = i2c_dev->base + STM32F4_I2C_CR2;
+
+	switch (c->count) {
+	case 1:
+		stm32f4_i2c_clr_bits(reg, STM32F4_I2C_CR2_IRQ_MASK);
+		stm32f4_i2c_read_msg(i2c_dev);
+		complete(&i2c_dev->complete);
+		break;
+	case 2:
+	case 3:
+		stm32f4_i2c_clr_bits(reg, STM32F4_I2C_CR2_ITBUFEN);
+		break;
+	default:
+		stm32f4_i2c_read_msg(i2c_dev);
+	}
+}
+
+/**
+ * stm32f4_i2c_handle_rx_btf() - Handle byte transfer finished interrupt
+ * in case of read
+ * @i2c_dev: Controller's private data
+ */
+static void stm32f4_i2c_handle_rx_btf(struct stm32f4_i2c_dev *i2c_dev)
+{
+	struct stm32f4_i2c_client *c = &i2c_dev->client;
+	void __iomem *reg;
+	u32 mask;
+	int i;
+
+	switch (c->count) {
+	case 2:
+		reg = i2c_dev->base + STM32F4_I2C_CR1;
+		/* Generate STOP or REPSTART */
+		if (c->stop)
+			stm32f4_i2c_set_bits(reg, STM32F4_I2C_CR1_STOP);
+		else
+			stm32f4_i2c_set_bits(reg, STM32F4_I2C_CR1_START);
+
+		/* Read two last data bytes */
+		for (i = 2; i > 0; i--)
+			stm32f4_i2c_read_msg(i2c_dev);
+
+		/* Disable EVT and ERR interrupt */
+		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:
+		/* Enable ACK and read 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_client *c = &i2c_dev->client;
+	void __iomem *reg;
+	u32 sr2;
+
+	switch (c->count) {
+	case 0:
+		stm32f4_i2c_terminate_xfer(i2c_dev);
+		/* Clear ADDR flag */
+		sr2 = readl_relaxed(i2c_dev->base + STM32F4_I2C_SR2);
+		break;
+	case 1:
+		/*
+		 * Single byte reception:
+		 * Enable NACK, clear ADDR flag and generate STOP or RepSTART
+		 */
+		reg = i2c_dev->base + STM32F4_I2C_CR1;
+		stm32f4_i2c_clr_bits(reg, STM32F4_I2C_CR1_ACK);
+		sr2 = readl_relaxed(i2c_dev->base + STM32F4_I2C_SR2);
+		if (c->stop)
+			stm32f4_i2c_set_bits(reg, STM32F4_I2C_CR1_STOP);
+		else
+			stm32f4_i2c_set_bits(reg, STM32F4_I2C_CR1_START);
+		break;
+	case 2:
+		/*
+		 * 2-byte reception:
+		 * Enable NACK and PEC Position Ack and clear ADDR flag
+		 */
+		reg = i2c_dev->base + STM32F4_I2C_CR1;
+		stm32f4_i2c_clr_bits(reg, STM32F4_I2C_CR1_ACK);
+		stm32f4_i2c_set_bits(reg, STM32F4_I2C_CR1_POS);
+		sr2 = readl_relaxed(i2c_dev->base + STM32F4_I2C_SR2);
+		break;
+
+	default:
+		/* N-byte reception: Enable ACK and clear ADDR flag */
+		reg = i2c_dev->base + STM32F4_I2C_CR1;
+		stm32f4_i2c_set_bits(reg, STM32F4_I2C_CR1_ACK);
+		sr2 = 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_client *c = &i2c_dev->client;
+	void __iomem *reg;
+	u32 real_status, possible_status, ien, sr2;
+	int flag;
+
+	ien = readl_relaxed(i2c_dev->base + STM32F4_I2C_CR2);
+	ien &= STM32F4_I2C_CR2_IRQ_MASK;
+
+	/* Check possible status combinations */
+	if (ien & STM32F4_I2C_CR2_ITEVTEN) {
+		possible_status = STM32F4_I2C_SR1_ITEVTEN_MASK;
+		if (ien & STM32F4_I2C_CR2_ITBUFEN)
+			possible_status |= STM32F4_I2C_SR1_ITBUFEN_MASK;
+	}
+
+	real_status = readl_relaxed(i2c_dev->base + STM32F4_I2C_SR1);
+
+	if (!(real_status & possible_status)) {
+		dev_dbg(i2c_dev->dev,
+			"spurious evt it (status=0x%08x, ien=0x%08x)\n",
+			real_status, ien);
+		return IRQ_NONE;
+	}
+
+	/* Use __fls() to check error bits first */
+	flag = __fls(real_status & possible_status);
+
+	switch (1 << flag) {
+	case STM32F4_I2C_SR1_SB:
+		stm32f4_i2c_write_byte(i2c_dev, c->addr);
+		break;
+
+	case STM32F4_I2C_SR1_ADDR:
+		if (c->addr & I2C_M_RD)
+			stm32f4_i2c_handle_rx_addr(i2c_dev);
+		else
+			sr2 = readl_relaxed(i2c_dev->base + STM32F4_I2C_SR2);
+
+		/* Enable ITBUF interrupts */
+		reg = i2c_dev->base + STM32F4_I2C_CR2;
+		stm32f4_i2c_set_bits(reg, STM32F4_I2C_CR2_ITBUFEN);
+		break;
+
+	case STM32F4_I2C_SR1_BTF:
+		if (c->addr & I2C_M_RD)
+			stm32f4_i2c_handle_rx_btf(i2c_dev);
+		else
+			stm32f4_i2c_handle_tx_btf(i2c_dev);
+		break;
+
+	case STM32F4_I2C_SR1_TXE:
+		stm32f4_i2c_handle_write(i2c_dev);
+		break;
+
+	case STM32F4_I2C_SR1_RXNE:
+		stm32f4_i2c_handle_read(i2c_dev);
+		break;
+
+	default:
+		dev_err(i2c_dev->dev,
+			"evt it unhandled: status=0x%08x)\n", real_status);
+		return IRQ_NONE;
+	}
+
+	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_client *c = &i2c_dev->client;
+	void __iomem *reg;
+	u32 real_status, possible_status, ien;
+	int flag;
+
+	ien = readl_relaxed(i2c_dev->base + STM32F4_I2C_CR2);
+	ien &= STM32F4_I2C_CR2_IRQ_MASK;
+
+	/* Check possible status combinations */
+	if (ien & STM32F4_I2C_CR2_ITERREN)
+		possible_status = STM32F4_I2C_SR1_ITERREN_MASK;
+
+	real_status = readl_relaxed(i2c_dev->base + STM32F4_I2C_SR1);
+
+	if (!(real_status & possible_status)) {
+		dev_dbg(i2c_dev->dev,
+			"spurious err it (status=0x%08x, ien=0x%08x)\n",
+			real_status, ien);
+		return IRQ_NONE;
+	}
+
+	/* Use __fls() to check error bits first */
+	flag = __fls(real_status & possible_status);
+
+	switch (1 << flag) {
+	case STM32F4_I2C_SR1_BERR:
+		reg = i2c_dev->base + STM32F4_I2C_SR1;
+		stm32f4_i2c_clr_bits(reg, STM32F4_I2C_SR1_BERR);
+		c->result = -EIO;
+		break;
+
+	case STM32F4_I2C_SR1_ARLO:
+		reg = i2c_dev->base + STM32F4_I2C_SR1;
+		stm32f4_i2c_clr_bits(reg, STM32F4_I2C_SR1_ARLO);
+		c->result = -EAGAIN;
+		break;
+
+	case STM32F4_I2C_SR1_AF:
+		reg = i2c_dev->base + STM32F4_I2C_CR1;
+		stm32f4_i2c_set_bits(reg, STM32F4_I2C_CR1_STOP);
+		c->result = -EIO;
+		break;
+
+	default:
+		dev_err(i2c_dev->dev,
+			"err it unhandled: status=0x%08x)\n", real_status);
+		return IRQ_NONE;
+	}
+
+	/* Reset I2C */
+	stm32f4_i2c_soft_reset(i2c_dev);
+
+	/* Disable interrupts */
+	reg = i2c_dev->base + STM32F4_I2C_CR2;
+	stm32f4_i2c_clr_bits(reg, STM32F4_I2C_CR2_IRQ_MASK);
+
+	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_client *c = &i2c_dev->client;
+	void __iomem *reg = i2c_dev->base + STM32F4_I2C_CR1;
+	unsigned long timeout;
+	u32 mask;
+	int ret;
+
+	c->addr = (u8)(msg->addr << 1);
+	c->addr	|= (msg->flags & I2C_M_RD);
+	c->buf = msg->buf;
+	c->count = msg->len;
+	c->result = 0;
+	c->stop	= is_last;
+
+	reinit_completion(&i2c_dev->complete);
+
+	/* Enable ITEVT and ITERR 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 = c->result;
+
+	/* Disable PEC position Ack */
+	stm32f4_i2c_clr_bits(reg, STM32F4_I2C_CR1_POS);
+
+	if (!timeout) {
+		dev_err(i2c_dev->dev, "Access to slave 0x%x timed out\n",
+			c->addr >> 1);
+		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;
+
+	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;
+	}
+
+	stm32f4_i2c_hw_config(i2c_dev);
+
+	for (i = 0; i < num && !ret; i++)
+		ret = stm32f4_i2c_xfer_msg(i2c_dev, &msgs[i], i == 0,
+					   i == num - 1);
+
+	clk_disable_unprepare(i2c_dev->clk);
+
+	i2c_dev->busy = false;
+
+	return (ret < 0) ? ret : i;
+}
+
+static u32 stm32f4_i2c_func(struct i2c_adapter *adap)
+{
+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
+}
+
+static 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 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_event = irq_of_parse_and_map(np, 0);
+	if (!i2c_dev->irq_event) {
+		dev_err(&pdev->dev, "IRQ missing or invalid\n");
+		return -EINVAL;
+	}
+
+	i2c_dev->irq_error = irq_of_parse_and_map(np, 1);
+	if (!i2c_dev->irq_error) {
+		dev_err(&pdev->dev, "IRQ 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);
+	}
+
+	i2c_dev->rst = devm_reset_control_get(&pdev->dev, NULL);
+	if (IS_ERR(i2c_dev->rst)) {
+		dev_err(&pdev->dev, "Error: Missing controller reset\n");
+		return PTR_ERR(i2c_dev->rst);
+	}
+
+	reset_control_assert(i2c_dev->rst);
+	udelay(2);
+	reset_control_deassert(i2c_dev->rst);
+
+	i2c_dev->speed = STM32F4_I2C_SPEED_STANDARD;
+	ret = of_property_read_u32(np, "clock-frequency", &clk_rate);
+	if ((!ret) && (clk_rate == 400000))
+		i2c_dev->speed = STM32F4_I2C_SPEED_FAST;
+
+	i2c_dev->dev = &pdev->dev;
+
+	ret = devm_request_threaded_irq(&pdev->dev, i2c_dev->irq_event,
+					NULL, stm32f4_i2c_isr_event,
+					IRQF_ONESHOT, pdev->name, i2c_dev);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed to request irq %i\n",
+			i2c_dev->irq_error);
+		return ret;
+	}
+
+	ret = devm_request_threaded_irq(&pdev->dev, i2c_dev->irq_error,
+					NULL, stm32f4_i2c_isr_error,
+					IRQF_ONESHOT, pdev->name, i2c_dev);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed to request irq %i\n",
+			i2c_dev->irq_error);
+		return ret;
+	}
+
+	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) {
+		dev_err(&pdev->dev, "Failed to add adapter\n");
+		return ret;
+	}
+
+	platform_set_drvdata(pdev, i2c_dev);
+
+	dev_info(i2c_dev->dev, "STM32F4 I2C driver initialized\n");
+
+	return 0;
+}
+
+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);
+
+	return 0;
+}
+
+static const struct of_device_id stm32f4_i2c_match[] = {
+	{ .compatible = "st,i2c-stm32f4", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, stm32f4_i2c_match);
+
+static struct platform_driver stm32f4_i2c_driver = {
+	.driver = {
+		.name = "i2c-stm32f4",
+		.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");
-- 
1.9.1