i2c: i2c-st: Add ST I2C controller

This patch adds support to SSC (Synchronous Serial Controller)
I2C driver. This IP also supports SPI protocol, but this is not
the aim of this driver.

This IP is embedded in all ST SoCs for Set-top box platorms, and
supports I2C Standard and Fast modes.
Signed-off-by: Maxime Coquelin <maxime.coquelin@st.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

Documentation/devicetree/bindings/i2c/i2c-st.txt

+ST SSC binding, for I2C mode operation
+
+Required properties :
+- compatible : Must be "st,comms-ssc-i2c" or "st,comms-ssc4-i2c"
+- reg : Offset and length of the register set for the device
+- interrupts : the interrupt specifier
+- clock-names: Must contain "ssc".
+- clocks: Must contain an entry for each name in clock-names. See the common
+  clock bindings.
+- A pinctrl state named "default" must be defined to set pins in mode of
+  operation for I2C transfer.
+
+Optional properties :
+- clock-frequency : Desired I2C bus clock frequency in Hz. If not specified,
+  the default 100 kHz frequency will be used. As only Normal and Fast modes
+  are supported, possible values are 100000 and 400000.
+- st,i2c-min-scl-pulse-width-us : The minimum valid SCL pulse width that is
+  allowed through the deglitch circuit. In units of us.
+- st,i2c-min-sda-pulse-width-us : The minimum valid SDA pulse width that is
+  allowed through the deglitch circuit. In units of us.
+- A pinctrl state named "idle" could be defined to set pins in idle state
+  when I2C instance is not performing a transfer.
+- A pinctrl state named "sleep" could be defined to set pins in sleep state
+  when driver enters in suspend.
+
+
+
+Example :
+
+i2c0: i2c@fed40000 {
+	compatible	= "st,comms-ssc4-i2c";
+	reg		= <0xfed40000 0x110>;
+	interrupts	=  <GIC_SPI 187 IRQ_TYPE_LEVEL_HIGH>;
+	clocks		= <&CLK_S_ICN_REG_0>;
+	clock-names	= "ssc";
+	clock-frequency = <400000>;
+	pinctrl-names	= "default";
+	pinctrl-0	= <&pinctrl_i2c0_default>;
+	st,i2c-min-scl-pulse-width-us = <0>;
+	st,i2c-min-sda-pulse-width-us = <5>;
+};

drivers/i2c/busses/Kconfig

@@ -702,6 +702,16 @@ config I2C_SIRF
 	  This driver can also be built as a module.  If so, the module
 	  will be called i2c-sirf.
 
+config I2C_ST
+	tristate "STMicroelectronics SSC I2C support"
+	depends on ARCH_STI
+	help
+	  Enable this option to add support for STMicroelectronics SoCs
+	  hardware SSC (Synchronous Serial Controller) as an I2C controller.
+
+	  This driver can also be built as module. If so, the module
+	  will be called i2c-st.
+
 config I2C_STU300
 	tristate "ST Microelectronics DDC I2C interface"
 	depends on MACH_U300

drivers/i2c/busses/Makefile

@@ -69,6 +69,7 @@ obj-$(CONFIG_I2C_SH7760)	+= i2c-sh7760.o
 obj-$(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_STU300)	+= i2c-stu300.o
 obj-$(CONFIG_I2C_TEGRA)		+= i2c-tegra.o
 obj-$(CONFIG_I2C_VERSATILE)	+= i2c-versatile.o

drivers/i2c/busses/i2c-st.c

+/*
+ * Copyright (C) 2013 STMicroelectronics
+ *
+ * I2C master mode controller driver, used in STMicroelectronics devices.
+ *
+ * Author: Maxime Coquelin <maxime.coquelin@st.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/i2c.h>
+#include <linux/clk.h>
+#include <linux/io.h>
+#include <linux/delay.h>
+#include <linux/interrupt.h>
+#include <linux/err.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+
+/* SSC registers */
+#define SSC_BRG				0x000
+#define SSC_TBUF			0x004
+#define SSC_RBUF			0x008
+#define SSC_CTL				0x00C
+#define SSC_IEN				0x010
+#define SSC_STA				0x014
+#define SSC_I2C				0x018
+#define SSC_SLAD			0x01C
+#define SSC_REP_START_HOLD		0x020
+#define SSC_START_HOLD			0x024
+#define SSC_REP_START_SETUP		0x028
+#define SSC_DATA_SETUP			0x02C
+#define SSC_STOP_SETUP			0x030
+#define SSC_BUS_FREE			0x034
+#define SSC_TX_FSTAT			0x038
+#define SSC_RX_FSTAT			0x03C
+#define SSC_PRE_SCALER_BRG		0x040
+#define SSC_CLR				0x080
+#define SSC_NOISE_SUPP_WIDTH		0x100
+#define SSC_PRSCALER			0x104
+#define SSC_NOISE_SUPP_WIDTH_DATAOUT	0x108
+#define SSC_PRSCALER_DATAOUT		0x10c
+
+/* SSC Control */
+#define SSC_CTL_DATA_WIDTH_9		0x8
+#define SSC_CTL_DATA_WIDTH_MSK		0xf
+#define SSC_CTL_BM			0xf
+#define SSC_CTL_HB			BIT(4)
+#define SSC_CTL_PH			BIT(5)
+#define SSC_CTL_PO			BIT(6)
+#define SSC_CTL_SR			BIT(7)
+#define SSC_CTL_MS			BIT(8)
+#define SSC_CTL_EN			BIT(9)
+#define SSC_CTL_LPB			BIT(10)
+#define SSC_CTL_EN_TX_FIFO		BIT(11)
+#define SSC_CTL_EN_RX_FIFO		BIT(12)
+#define SSC_CTL_EN_CLST_RX		BIT(13)
+
+/* SSC Interrupt Enable */
+#define SSC_IEN_RIEN			BIT(0)
+#define SSC_IEN_TIEN			BIT(1)
+#define SSC_IEN_TEEN			BIT(2)
+#define SSC_IEN_REEN			BIT(3)
+#define SSC_IEN_PEEN			BIT(4)
+#define SSC_IEN_AASEN			BIT(6)
+#define SSC_IEN_STOPEN			BIT(7)
+#define SSC_IEN_ARBLEN			BIT(8)
+#define SSC_IEN_NACKEN			BIT(10)
+#define SSC_IEN_REPSTRTEN		BIT(11)
+#define SSC_IEN_TX_FIFO_HALF		BIT(12)
+#define SSC_IEN_RX_FIFO_HALF_FULL	BIT(14)
+
+/* SSC Status */
+#define SSC_STA_RIR			BIT(0)
+#define SSC_STA_TIR			BIT(1)
+#define SSC_STA_TE			BIT(2)
+#define SSC_STA_RE			BIT(3)
+#define SSC_STA_PE			BIT(4)
+#define SSC_STA_CLST			BIT(5)
+#define SSC_STA_AAS			BIT(6)
+#define SSC_STA_STOP			BIT(7)
+#define SSC_STA_ARBL			BIT(8)
+#define SSC_STA_BUSY			BIT(9)
+#define SSC_STA_NACK			BIT(10)
+#define SSC_STA_REPSTRT			BIT(11)
+#define SSC_STA_TX_FIFO_HALF		BIT(12)
+#define SSC_STA_TX_FIFO_FULL		BIT(13)
+#define SSC_STA_RX_FIFO_HALF		BIT(14)
+
+/* SSC I2C Control */
+#define SSC_I2C_I2CM			BIT(0)
+#define SSC_I2C_STRTG			BIT(1)
+#define SSC_I2C_STOPG			BIT(2)
+#define SSC_I2C_ACKG			BIT(3)
+#define SSC_I2C_AD10			BIT(4)
+#define SSC_I2C_TXENB			BIT(5)
+#define SSC_I2C_REPSTRTG		BIT(11)
+#define SSC_I2C_SLAVE_DISABLE		BIT(12)
+
+/* SSC Tx FIFO Status */
+#define SSC_TX_FSTAT_STATUS		0x07
+
+/* SSC Rx FIFO Status */
+#define SSC_RX_FSTAT_STATUS		0x07
+
+/* SSC Clear bit operation */
+#define SSC_CLR_SSCAAS			BIT(6)
+#define SSC_CLR_SSCSTOP			BIT(7)
+#define SSC_CLR_SSCARBL			BIT(8)
+#define SSC_CLR_NACK			BIT(10)
+#define SSC_CLR_REPSTRT			BIT(11)
+
+/* SSC Clock Prescaler */
+#define SSC_PRSC_VALUE			0x0f
+
+
+#define SSC_TXFIFO_SIZE			0x8
+#define SSC_RXFIFO_SIZE			0x8
+
+enum st_i2c_mode {
+	I2C_MODE_STANDARD,
+	I2C_MODE_FAST,
+	I2C_MODE_END,
+};
+
+/**
+ * struct st_i2c_timings - per-Mode tuning parameters
+ * @rate: I2C bus rate
+ * @rep_start_hold: I2C repeated start hold time requirement
+ * @rep_start_setup: I2C repeated start set up time requirement
+ * @start_hold: I2C start hold time requirement
+ * @data_setup_time: I2C data set up time requirement
+ * @stop_setup_time: I2C stop set up time requirement
+ * @bus_free_time: I2C bus free time requirement
+ * @sda_pulse_min_limit: I2C SDA pulse mini width limit
+ */
+struct st_i2c_timings {
+	u32 rate;
+	u32 rep_start_hold;
+	u32 rep_start_setup;
+	u32 start_hold;
+	u32 data_setup_time;
+	u32 stop_setup_time;
+	u32 bus_free_time;
+	u32 sda_pulse_min_limit;
+};
+
+/**
+ * struct st_i2c_client - client specific data
+ * @addr: 8-bit slave addr, including r/w bit
+ * @count: number of bytes to be transfered
+ * @xfered: number of bytes already transferred
+ * @buf: data buffer
+ * @result: result of the transfer
+ * @stop: last I2C msg to be sent, i.e. STOP to be generated
+ */
+struct st_i2c_client {
+	u8	addr;
+	u32	count;
+	u32	xfered;
+	u8	*buf;
+	int	result;
+	bool	stop;
+};
+
+/**
+ * struct st_i2c_dev - private data of the controller
+ * @adap: I2C adapter for this controller
+ * @dev: device for this controller
+ * @base: virtual memory area
+ * @complete: completion of I2C message
+ * @irq: interrupt line for th controller
+ * @clk: hw ssc block clock
+ * @mode: I2C mode of the controller. Standard or Fast only supported
+ * @scl_min_width_us: SCL line minimum pulse width in us
+ * @sda_min_width_us: SDA line minimum pulse width in us
+ * @client: I2C transfert information
+ * @busy: I2C transfer on-going
+ */
+struct st_i2c_dev {
+	struct i2c_adapter	adap;
+	struct device		*dev;
+	void __iomem		*base;
+	struct completion	complete;
+	int			irq;
+	struct clk		*clk;
+	int			mode;
+	u32			scl_min_width_us;
+	u32			sda_min_width_us;
+	struct st_i2c_client	client;
+	bool			busy;
+};
+
+static inline void st_i2c_set_bits(void __iomem *reg, u32 mask)
+{
+	writel_relaxed(readl_relaxed(reg) | mask, reg);
+}
+
+static inline void st_i2c_clr_bits(void __iomem *reg, u32 mask)
+{
+	writel_relaxed(readl_relaxed(reg) & ~mask, reg);
+}
+
+/* From I2C Specifications v0.5 */
+static struct st_i2c_timings i2c_timings[] = {
+	[I2C_MODE_STANDARD] = {
+		.rate			= 100000,
+		.rep_start_hold		= 4000,
+		.rep_start_setup	= 4700,
+		.start_hold		= 4000,
+		.data_setup_time	= 250,
+		.stop_setup_time	= 4000,
+		.bus_free_time		= 4700,
+	},
+	[I2C_MODE_FAST] = {
+		.rate			= 400000,
+		.rep_start_hold		= 600,
+		.rep_start_setup	= 600,
+		.start_hold		= 600,
+		.data_setup_time	= 100,
+		.stop_setup_time	= 600,
+		.bus_free_time		= 1300,
+	},
+};
+
+static void st_i2c_flush_rx_fifo(struct st_i2c_dev *i2c_dev)
+{
+	int count, i;
+
+	/*
+	 * Counter only counts up to 7 but fifo size is 8...
+	 * When fifo is full, counter is 0 and RIR bit of status register is
+	 * set
+	 */
+	if (readl_relaxed(i2c_dev->base + SSC_STA) & SSC_STA_RIR)
+		count = SSC_RXFIFO_SIZE;
+	else
+		count = readl_relaxed(i2c_dev->base + SSC_RX_FSTAT) &
+			SSC_RX_FSTAT_STATUS;
+
+	for (i = 0; i < count; i++)
+		readl_relaxed(i2c_dev->base + SSC_RBUF);
+}
+
+static void st_i2c_soft_reset(struct st_i2c_dev *i2c_dev)
+{
+	/*
+	 * FIFO needs to be emptied before reseting the IP,
+	 * else the controller raises a BUSY error.
+	 */
+	st_i2c_flush_rx_fifo(i2c_dev);
+
+	st_i2c_set_bits(i2c_dev->base + SSC_CTL, SSC_CTL_SR);
+	st_i2c_clr_bits(i2c_dev->base + SSC_CTL, SSC_CTL_SR);
+}
+
+/**
+ * st_i2c_hw_config() - Prepare SSC block, calculate and apply tuning timings
+ * @i2c_dev: Controller's private data
+ */
+static void st_i2c_hw_config(struct st_i2c_dev *i2c_dev)
+{
+	unsigned long rate;
+	u32 val, ns_per_clk;
+	struct st_i2c_timings *t = &i2c_timings[i2c_dev->mode];
+
+	st_i2c_soft_reset(i2c_dev);
+
+	val = SSC_CLR_REPSTRT | SSC_CLR_NACK | SSC_CLR_SSCARBL |
+		SSC_CLR_SSCAAS | SSC_CLR_SSCSTOP;
+	writel_relaxed(val, i2c_dev->base + SSC_CLR);
+
+	/* SSC Control register setup */
+	val = SSC_CTL_PO | SSC_CTL_PH | SSC_CTL_HB | SSC_CTL_DATA_WIDTH_9;
+	writel_relaxed(val, i2c_dev->base + SSC_CTL);
+
+	rate = clk_get_rate(i2c_dev->clk);
+	ns_per_clk = 1000000000 / rate;
+
+	/* Baudrate */
+	val = rate / (2 * t->rate);
+	writel_relaxed(val, i2c_dev->base + SSC_BRG);
+
+	/* Pre-scaler baudrate */
+	writel_relaxed(1, i2c_dev->base + SSC_PRE_SCALER_BRG);
+
+	/* Enable I2C mode */
+	writel_relaxed(SSC_I2C_I2CM, i2c_dev->base + SSC_I2C);
+
+	/* Repeated start hold time */
+	val = t->rep_start_hold / ns_per_clk;
+	writel_relaxed(val, i2c_dev->base + SSC_REP_START_HOLD);
+
+	/* Repeated start set up time */
+	val = t->rep_start_setup / ns_per_clk;
+	writel_relaxed(val, i2c_dev->base + SSC_REP_START_SETUP);
+
+	/* Start hold time */
+	val = t->start_hold / ns_per_clk;
+	writel_relaxed(val, i2c_dev->base + SSC_START_HOLD);
+
+	/* Data set up time */
+	val = t->data_setup_time / ns_per_clk;
+	writel_relaxed(val, i2c_dev->base + SSC_DATA_SETUP);
+
+	/* Stop set up time */
+	val = t->stop_setup_time / ns_per_clk;
+	writel_relaxed(val, i2c_dev->base + SSC_STOP_SETUP);
+
+	/* Bus free time */
+	val = t->bus_free_time / ns_per_clk;
+	writel_relaxed(val, i2c_dev->base + SSC_BUS_FREE);
+
+	/* Prescalers set up */
+	val = rate / 10000000;
+	writel_relaxed(val, i2c_dev->base + SSC_PRSCALER);
+	writel_relaxed(val, i2c_dev->base + SSC_PRSCALER_DATAOUT);
+
+	/* Noise suppression witdh */
+	val = i2c_dev->scl_min_width_us * rate / 100000000;
+	writel_relaxed(val, i2c_dev->base + SSC_NOISE_SUPP_WIDTH);
+
+	/* Noise suppression max output data delay width */
+	val = i2c_dev->sda_min_width_us * rate / 100000000;
+	writel_relaxed(val, i2c_dev->base + SSC_NOISE_SUPP_WIDTH_DATAOUT);
+}
+
+static int st_i2c_wait_free_bus(struct st_i2c_dev *i2c_dev)
+{
+	u32 sta;
+	int i;
+
+	for (i = 0; i < 10; i++) {
+		sta = readl_relaxed(i2c_dev->base + SSC_STA);
+		if (!(sta & SSC_STA_BUSY))
+			return 0;
+
+		usleep_range(2000, 4000);
+	}
+
+	dev_err(i2c_dev->dev, "bus not free (status = 0x%08x)\n", sta);
+
+	return -EBUSY;
+}
+
+/**
+ * st_i2c_write_tx_fifo() - Write a byte in the Tx FIFO
+ * @i2c_dev: Controller's private data
+ * @byte: Data to write in the Tx FIFO
+ */
+static inline void st_i2c_write_tx_fifo(struct st_i2c_dev *i2c_dev, u8 byte)
+{
+	u16 tbuf = byte << 1;
+
+	writel_relaxed(tbuf | 1, i2c_dev->base + SSC_TBUF);
+}
+
+/**
+ * st_i2c_wr_fill_tx_fifo() - Fill the Tx FIFO in write mode
+ * @i2c_dev: Controller's private data
+ *
+ * This functions fills the Tx FIFO with I2C transfert buffer when
+ * in write mode.
+ */
+static void st_i2c_wr_fill_tx_fifo(struct st_i2c_dev *i2c_dev)
+{
+	struct st_i2c_client *c = &i2c_dev->client;
+	u32 tx_fstat, sta;
+	int i;
+
+	sta = readl_relaxed(i2c_dev->base + SSC_STA);
+	if (sta & SSC_STA_TX_FIFO_FULL)
+		return;
+
+	tx_fstat = readl_relaxed(i2c_dev->base + SSC_TX_FSTAT);
+	tx_fstat &= SSC_TX_FSTAT_STATUS;
+
+	if (c->count < (SSC_TXFIFO_SIZE - tx_fstat))
+		i = c->count;
+	else
+		i = SSC_TXFIFO_SIZE - tx_fstat;
+
+	for (; i > 0; i--, c->count--, c->buf++)
+		st_i2c_write_tx_fifo(i2c_dev, *c->buf);
+}
+
+/**
+ * st_i2c_rd_fill_tx_fifo() - Fill the Tx FIFO in read mode
+ * @i2c_dev: Controller's private data
+ *
+ * This functions fills the Tx FIFO with fixed pattern when
+ * in read mode to trigger clock.
+ */
+static void st_i2c_rd_fill_tx_fifo(struct st_i2c_dev *i2c_dev, int max)
+{
+	struct st_i2c_client *c = &i2c_dev->client;
+	u32 tx_fstat, sta;
+	int i;
+
+	sta = readl_relaxed(i2c_dev->base + SSC_STA);
+	if (sta & SSC_STA_TX_FIFO_FULL)
+		return;
+
+	tx_fstat = readl_relaxed(i2c_dev->base + SSC_TX_FSTAT);
+	tx_fstat &= SSC_TX_FSTAT_STATUS;
+
+	if (max < (SSC_TXFIFO_SIZE - tx_fstat))
+		i = max;
+	else
+		i = SSC_TXFIFO_SIZE - tx_fstat;
+
+	for (; i > 0; i--, c->xfered++)
+		st_i2c_write_tx_fifo(i2c_dev, 0xff);
+}
+
+static void st_i2c_read_rx_fifo(struct st_i2c_dev *i2c_dev)
+{
+	struct st_i2c_client *c = &i2c_dev->client;
+	u32 i, sta;
+	u16 rbuf;
+
+	sta = readl_relaxed(i2c_dev->base + SSC_STA);
+	if (sta & SSC_STA_RIR) {
+		i = SSC_RXFIFO_SIZE;
+	} else {
+		i = readl_relaxed(i2c_dev->base + SSC_RX_FSTAT);
+		i &= SSC_RX_FSTAT_STATUS;
+	}
+
+	for (; (i > 0) && (c->count > 0); i--, c->count--) {
+		rbuf = readl_relaxed(i2c_dev->base + SSC_RBUF) >> 1;
+		*c->buf++ = (u8)rbuf & 0xff;
+	}
+
+	if (i) {
+		dev_err(i2c_dev->dev, "Unexpected %d bytes in rx fifo\n", i);
+		st_i2c_flush_rx_fifo(i2c_dev);
+	}
+}
+
+/**
+ * st_i2c_terminate_xfer() - Send either STOP or REPSTART condition
+ * @i2c_dev: Controller's private data
+ */
+static void st_i2c_terminate_xfer(struct st_i2c_dev *i2c_dev)
+{
+	struct st_i2c_client *c = &i2c_dev->client;
+
+	st_i2c_clr_bits(i2c_dev->base + SSC_IEN, SSC_IEN_TEEN);
+	st_i2c_clr_bits(i2c_dev->base + SSC_I2C, SSC_I2C_STRTG);
+
+	if (c->stop) {
+		st_i2c_set_bits(i2c_dev->base + SSC_IEN, SSC_IEN_STOPEN);
+		st_i2c_set_bits(i2c_dev->base + SSC_I2C, SSC_I2C_STOPG);
+	} else {
+		st_i2c_set_bits(i2c_dev->base + SSC_IEN, SSC_IEN_REPSTRTEN);
+		st_i2c_set_bits(i2c_dev->base + SSC_I2C, SSC_I2C_REPSTRTG);
+	}
+}
+
+/**
+ * st_i2c_handle_write() - Handle FIFO empty interrupt in case of write
+ * @i2c_dev: Controller's private data
+ */
+static void st_i2c_handle_write(struct st_i2c_dev *i2c_dev)
+{
+	struct st_i2c_client *c = &i2c_dev->client;
+
+	st_i2c_flush_rx_fifo(i2c_dev);
+
+	if (!c->count)
+		/* End of xfer, send stop or repstart */
+		st_i2c_terminate_xfer(i2c_dev);
+	else
+		st_i2c_wr_fill_tx_fifo(i2c_dev);
+}
+
+/**
+ * st_i2c_handle_write() - Handle FIFO enmpty interrupt in case of read
+ * @i2c_dev: Controller's private data
+ */
+static void st_i2c_handle_read(struct st_i2c_dev *i2c_dev)
+{
+	struct st_i2c_client *c = &i2c_dev->client;
+	u32 ien;
+
+	/* Trash the address read back */
+	if (!c->xfered) {
+		readl_relaxed(i2c_dev->base + SSC_RBUF);
+		st_i2c_clr_bits(i2c_dev->base + SSC_I2C, SSC_I2C_TXENB);
+	} else {
+		st_i2c_read_rx_fifo(i2c_dev);
+	}
+
+	if (!c->count) {
+		/* End of xfer, send stop or repstart */
+		st_i2c_terminate_xfer(i2c_dev);
+	} else if (c->count == 1) {
+		/* Penultimate byte to xfer, disable ACK gen. */
+		st_i2c_clr_bits(i2c_dev->base + SSC_I2C, SSC_I2C_ACKG);
+
+		/* Last received byte is to be handled by NACK interrupt */
+		ien = SSC_IEN_NACKEN | SSC_IEN_ARBLEN;
+		writel_relaxed(ien, i2c_dev->base + SSC_IEN);
+
+		st_i2c_rd_fill_tx_fifo(i2c_dev, c->count);
+	} else {
+		st_i2c_rd_fill_tx_fifo(i2c_dev, c->count - 1);
+	}
+}
+
+/**
+ * st_i2c_isr() - Interrupt routine
+ * @irq: interrupt number
+ * @data: Controller's private data
+ */
+static irqreturn_t st_i2c_isr_thread(int irq, void *data)
+{
+	struct st_i2c_dev *i2c_dev = data;
+	struct st_i2c_client *c = &i2c_dev->client;
+	u32 sta, ien;
+	int it;
+
+	ien = readl_relaxed(i2c_dev->base + SSC_IEN);
+	sta = readl_relaxed(i2c_dev->base + SSC_STA);
+
+	/* Use __fls() to check error bits first */
+	it = __fls(sta & ien);
+	if (it < 0) {
+		dev_dbg(i2c_dev->dev, "spurious it (sta=0x%04x, ien=0x%04x)\n",
+				sta, ien);
+		return IRQ_NONE;
+	}
+
+	switch (1 << it) {
+	case SSC_STA_TE:
+		if (c->addr & I2C_M_RD)
+			st_i2c_handle_read(i2c_dev);
+		else
+			st_i2c_handle_write(i2c_dev);
+		break;
+
+	case SSC_STA_STOP:
+	case SSC_STA_REPSTRT:
+		writel_relaxed(0, i2c_dev->base + SSC_IEN);
+		complete(&i2c_dev->complete);
+		break;
+
+	case SSC_STA_NACK:
+		writel_relaxed(SSC_CLR_NACK, i2c_dev->base + SSC_CLR);
+
+		/* Last received byte handled by NACK interrupt */
+		if ((c->addr & I2C_M_RD) && (c->count == 1) && (c->xfered)) {
+			st_i2c_handle_read(i2c_dev);
+			break;
+		}
+
+		it = SSC_IEN_STOPEN | SSC_IEN_ARBLEN;
+		writel_relaxed(it, i2c_dev->base + SSC_IEN);
+
+		st_i2c_set_bits(i2c_dev->base + SSC_I2C, SSC_I2C_STOPG);
+		c->result = -EIO;
+		break;
+
+	case SSC_STA_ARBL:
+		writel_relaxed(SSC_CLR_SSCARBL, i2c_dev->base + SSC_CLR);
+
+		it = SSC_IEN_STOPEN | SSC_IEN_ARBLEN;
+		writel_relaxed(it, i2c_dev->base + SSC_IEN);
+
+		st_i2c_set_bits(i2c_dev->base + SSC_I2C, SSC_I2C_STOPG);
+		c->result = -EIO;
+		break;
+
+	default:
+		dev_err(i2c_dev->dev,
+				"it %d unhandled (sta=0x%04x)\n", it, sta);
+	}
+
+	/*
+	 * Read IEN register to ensure interrupt mask write is effective
+	 * before re-enabling interrupt at GIC level, and thus avoid spurious
+	 * interrupts.
+	 */
+	readl(i2c_dev->base + SSC_IEN);
+
+	return IRQ_HANDLED;
+}
+
+/**
+ * st_i2c_xfer_msg() - Transfer a single I2C message
+ * @i2c_dev: Controller's private data
+ * @msg: I2C message to transfer
+ * @is_first: first message of the sequence
+ * @is_last: last message of the sequence
+ */
+static int st_i2c_xfer_msg(struct st_i2c_dev *i2c_dev, struct i2c_msg *msg,
+			    bool is_first, bool is_last)
+{
+	struct st_i2c_client *c = &i2c_dev->client;
+	u32 ctl, i2c, it;
+	unsigned long timeout;
+	int ret;
+
+	c->addr		= (u8)(msg->addr << 1);
+	c->addr		|= (msg->flags & I2C_M_RD);
+	c->buf		= msg->buf;
+	c->count	= msg->len;
+	c->xfered	= 0;
+	c->result	= 0;
+	c->stop		= is_last;
+
+	INIT_COMPLETION(i2c_dev->complete);
+
+	ctl = SSC_CTL_EN | SSC_CTL_MS |	SSC_CTL_EN_RX_FIFO | SSC_CTL_EN_TX_FIFO;
+	st_i2c_set_bits(i2c_dev->base + SSC_CTL, ctl);
+
+	i2c = SSC_I2C_TXENB;
+	if (c->addr & I2C_M_RD)
+		i2c |= SSC_I2C_ACKG;
+	st_i2c_set_bits(i2c_dev->base + SSC_I2C, i2c);
+
+	/* Write slave address */
+	st_i2c_write_tx_fifo(i2c_dev, c->addr);
+
+	/* Pre-fill Tx fifo with data in case of write */
+	if (!(c->addr & I2C_M_RD))
+		st_i2c_wr_fill_tx_fifo(i2c_dev);
+
+	it = SSC_IEN_NACKEN | SSC_IEN_TEEN | SSC_IEN_ARBLEN;
+	writel_relaxed(it, i2c_dev->base + SSC_IEN);
+
+	if (is_first) {
+		ret = st_i2c_wait_free_bus(i2c_dev);
+		if (ret)
+			return ret;
+
+		st_i2c_set_bits(i2c_dev->base + SSC_I2C, SSC_I2C_STRTG);
+	}
+
+	timeout = wait_for_completion_timeout(&i2c_dev->complete,
+			i2c_dev->adap.timeout);
+	ret = c->result;
+
+	if (!timeout) {
+		dev_err(i2c_dev->dev, "Write to slave 0x%x timed out\n",
+				c->addr);
+		ret = -ETIMEDOUT;
+	}
+
+	i2c = SSC_I2C_STOPG | SSC_I2C_REPSTRTG;
+	st_i2c_clr_bits(i2c_dev->base + SSC_I2C, i2c);
+
+	writel_relaxed(SSC_CLR_SSCSTOP | SSC_CLR_REPSTRT,
+			i2c_dev->base + SSC_CLR);
+
+	return ret;
+}
+
+/**
+ * st_i2c_xfer() - Transfer a single I2C message
+ * @i2c_adap: Adapter pointer to the controller
+ * @msgs: Pointer to data to be written.
+ * @num: Number of messages to be executed
+ */
+static int st_i2c_xfer(struct i2c_adapter *i2c_adap,
+			struct i2c_msg msgs[], int num)
+{
+	struct st_i2c_dev *i2c_dev = i2c_get_adapdata(i2c_adap);
+	int ret, i;
+
+	i2c_dev->busy = true;
+
+	ret = clk_prepare_enable(i2c_dev->clk);
+	if (ret) {
+		dev_err(i2c_dev->dev, "Failed to prepare_enable clock\n");
+		return ret;
+	}
+
+	pinctrl_pm_select_default_state(i2c_dev->dev);
+
+	st_i2c_hw_config(i2c_dev);
+
+	for (i = 0; (i < num) && !ret; i++)
+		ret = st_i2c_xfer_msg(i2c_dev, &msgs[i], i == 0, i == num - 1);
+
+	pinctrl_pm_select_idle_state(i2c_dev->dev);
+
+	clk_disable_unprepare(i2c_dev->clk);
+
+	i2c_dev->busy = false;
+
+	return (ret < 0) ? ret : i;
+}
+
+#ifdef CONFIG_PM_SLEEP
+static int st_i2c_suspend(struct device *dev)
+{
+	struct platform_device *pdev =
+		container_of(dev, struct platform_device, dev);
+	struct st_i2c_dev *i2c_dev = platform_get_drvdata(pdev);
+
+	if (i2c_dev->busy)
+		return -EBUSY;
+
+	pinctrl_pm_select_sleep_state(dev);
+
+	return 0;
+}
+
+static int st_i2c_resume(struct device *dev)
+{
+	pinctrl_pm_select_default_state(dev);
+	/* Go in idle state if available */
+	pinctrl_pm_select_idle_state(dev);
+
+	return 0;
+}
+
+static SIMPLE_DEV_PM_OPS(st_i2c_pm, st_i2c_suspend, st_i2c_resume);
+#define ST_I2C_PM	(&st_i2c_pm)
+#else
+#define ST_I2C_PM	NULL
+#endif
+
+static u32 st_i2c_func(struct i2c_adapter *adap)
+{
+	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
+}
+
+static struct i2c_algorithm st_i2c_algo = {
+	.master_xfer = st_i2c_xfer,
+	.functionality = st_i2c_func,
+};
+
+static int st_i2c_of_get_deglitch(struct device_node *np,
+		struct st_i2c_dev *i2c_dev)
+{
+	int ret;
+
+	ret = of_property_read_u32(np, "st,i2c-min-scl-pulse-width-us",
+			&i2c_dev->scl_min_width_us);
+	if ((ret == -ENODATA) || (ret == -EOVERFLOW)) {
+		dev_err(i2c_dev->dev, "st,i2c-min-scl-pulse-width-us invalid\n");
+		return ret;
+	}
+
+	ret = of_property_read_u32(np, "st,i2c-min-sda-pulse-width-us",
+			&i2c_dev->sda_min_width_us);
+	if ((ret == -ENODATA) || (ret == -EOVERFLOW)) {
+		dev_err(i2c_dev->dev, "st,i2c-min-sda-pulse-width-us invalid\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static int st_i2c_probe(struct platform_device *pdev)
+{
+	struct device_node *np = pdev->dev.of_node;
+	struct st_i2c_dev *i2c_dev;
+	struct resource *res;
+	u32 clk_rate;
+	struct i2c_adapter *adap;
+	int ret;
+
+	i2c_dev = devm_kzalloc(&pdev->dev, sizeof(*i2c_dev), GFP_KERNEL);
+	if (!i2c_dev)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	i2c_dev->base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(i2c_dev->base))
+		return PTR_ERR(i2c_dev->base);
+
+	i2c_dev->irq = irq_of_parse_and_map(np, 0);
+	if (!i2c_dev->irq) {
+		dev_err(&pdev->dev, "IRQ missing or invalid\n");
+		return -EINVAL;
+	}
+
+	i2c_dev->clk = of_clk_get_by_name(np, "ssc");
+	if (IS_ERR(i2c_dev->clk)) {
+		dev_err(&pdev->dev, "Unable to request clock\n");
+		return PTR_ERR(i2c_dev->clk);
+	}
+
+	i2c_dev->mode = I2C_MODE_STANDARD;
+	ret = of_property_read_u32(np, "clock-frequency", &clk_rate);
+	if ((!ret) && (clk_rate == 400000))
+		i2c_dev->mode = I2C_MODE_FAST;
+
+	i2c_dev->dev = &pdev->dev;
+
+	ret = devm_request_threaded_irq(&pdev->dev, i2c_dev->irq,
+			NULL, st_i2c_isr_thread,
+			IRQF_ONESHOT, pdev->name, i2c_dev);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed to request irq %i\n", i2c_dev->irq);
+		return ret;
+	}
+
+	pinctrl_pm_select_default_state(i2c_dev->dev);
+	/* In case idle state available, select it */
+	pinctrl_pm_select_idle_state(i2c_dev->dev);
+
+	ret = st_i2c_of_get_deglitch(np, i2c_dev);
+	if (ret)
+		return ret;
+
+	adap = &i2c_dev->adap;
+	i2c_set_adapdata(adap, i2c_dev);
+	snprintf(adap->name, sizeof(adap->name), "ST I2C(0x%x)", res->start);
+	adap->owner = THIS_MODULE;
+	adap->timeout = 2 * HZ;
+	adap->retries = 0;
+	adap->algo = &st_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, "%s initialized\n", adap->name);
+
+	return 0;
+}
+
+static int st_i2c_remove(struct platform_device *pdev)
+{
+	struct st_i2c_dev *i2c_dev = platform_get_drvdata(pdev);
+
+	i2c_del_adapter(&i2c_dev->adap);
+
+	return 0;
+}
+
+static struct of_device_id st_i2c_match[] = {
+	{ .compatible = "st,comms-ssc-i2c", },
+	{ .compatible = "st,comms-ssc4-i2c", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, st_i2c_match);
+
+static struct platform_driver st_i2c_driver = {
+	.driver = {
+		.name = "st-i2c",
+		.owner = THIS_MODULE,
+		.of_match_table = st_i2c_match,
+		.pm = ST_I2C_PM,
+	},
+	.probe = st_i2c_probe,
+	.remove = st_i2c_remove,
+};
+
+module_platform_driver(st_i2c_driver);
+
+MODULE_AUTHOR("Maxime Coquelin <maxime.coquelin@st.com>");
+MODULE_DESCRIPTION("STMicroelectronics I2C driver");
+MODULE_LICENSE("GPL v2");