i2c: ST DDC I2C U300 bus driver v3

This adds support for the ST Microelectronics DDC I2C bus
driver. This bus is used in the U300 architecture recently
added to RMK:s ARM tree.

Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>
Reviewed-by: Ben Dooks <ben-linux@fluff.org>
Reviewed-by: Jean Delvare <khali@linus-fr.org>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>

3 files changed, 1042 insertions, 0 deletions

diff --git a/drivers/i2c/busses/Kconfig b/drivers/i2c/busses/Kconfig
index 0d04d3ebfc2d..0e0a39040835 100644
--- a/drivers/i2c/busses/Kconfig
+++ b/drivers/i2c/busses/Kconfig
@@ -513,6 +513,18 @@ config I2C_SIMTEC
 	  This driver can also be built as a module. If so, the module
 	  will be called i2c-simtec.
 
+config I2C_STU300
+	tristate "ST Microelectronics DDC I2C interface"
+	default y if MACH_U300
+	help
+	  If you say yes to this option, support will be included for the
+	  I2C interface from ST Microelectronics simply called "DDC I2C"
+	  supporting both I2C and DDC, used in e.g. the U300 series
+	  mobile platforms.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called i2c-stu300.
+
 config I2C_VERSATILE
 	tristate "ARM Versatile/Realview I2C bus support"
 	depends on ARCH_VERSATILE || ARCH_REALVIEW
diff --git a/drivers/i2c/busses/Makefile b/drivers/i2c/busses/Makefile
index 776acb6403a7..edeabf003106 100644
--- a/drivers/i2c/busses/Makefile
+++ b/drivers/i2c/busses/Makefile
@@ -48,6 +48,7 @@ obj-$(CONFIG_I2C_S6000)		+= i2c-s6000.o
 obj-$(CONFIG_I2C_SH7760)	+= i2c-sh7760.o
 obj-$(CONFIG_I2C_SH_MOBILE)	+= i2c-sh_mobile.o
 obj-$(CONFIG_I2C_SIMTEC)	+= i2c-simtec.o
+obj-$(CONFIG_I2C_STU300)	+= i2c-stu300.o
 obj-$(CONFIG_I2C_VERSATILE)	+= i2c-versatile.o
 
 # External I2C/SMBus adapter drivers
diff --git a/drivers/i2c/busses/i2c-stu300.c b/drivers/i2c/busses/i2c-stu300.c
new file mode 100644
index 000000000000..182e711318ba
--- /dev/null
+++ b/drivers/i2c/busses/i2c-stu300.c
@@ -0,0 +1,1029 @@
+/*
+ * Copyright (C) 2007-2009 ST-Ericsson AB
+ * License terms: GNU General Public License (GPL) version 2
+ * ST DDC I2C master mode driver, used in e.g. U300 series platforms.
+ * Author: Linus Walleij <linus.walleij@stericsson.com>
+ * Author: Jonas Aaberg <jonas.aberg@stericsson.com>
+ */
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/platform_device.h>
+#include <linux/delay.h>
+#include <linux/i2c.h>
+#include <linux/spinlock.h>
+#include <linux/completion.h>
+#include <linux/err.h>
+#include <linux/interrupt.h>
+#include <linux/clk.h>
+#include <linux/io.h>
+
+/* the name of this kernel module */
+#define NAME "stu300"
+
+/* CR (Control Register) 8bit (R/W) */
+#define I2C_CR					(0x00000000)
+#define I2C_CR_RESET_VALUE			(0x00)
+#define I2C_CR_RESET_UMASK			(0x00)
+#define I2C_CR_DDC1_ENABLE			(0x80)
+#define I2C_CR_TRANS_ENABLE			(0x40)
+#define I2C_CR_PERIPHERAL_ENABLE		(0x20)
+#define I2C_CR_DDC2B_ENABLE			(0x10)
+#define I2C_CR_START_ENABLE			(0x08)
+#define I2C_CR_ACK_ENABLE			(0x04)
+#define I2C_CR_STOP_ENABLE			(0x02)
+#define I2C_CR_INTERRUPT_ENABLE			(0x01)
+/* SR1 (Status Register 1) 8bit (R/-) */
+#define I2C_SR1					(0x00000004)
+#define I2C_SR1_RESET_VALUE			(0x00)
+#define I2C_SR1_RESET_UMASK			(0x00)
+#define I2C_SR1_EVF_IND				(0x80)
+#define I2C_SR1_ADD10_IND			(0x40)
+#define I2C_SR1_TRA_IND				(0x20)
+#define I2C_SR1_BUSY_IND			(0x10)
+#define I2C_SR1_BTF_IND				(0x08)
+#define I2C_SR1_ADSL_IND			(0x04)
+#define I2C_SR1_MSL_IND				(0x02)
+#define I2C_SR1_SB_IND				(0x01)
+/* SR2 (Status Register 2) 8bit (R/-) */
+#define I2C_SR2					(0x00000008)
+#define I2C_SR2_RESET_VALUE			(0x00)
+#define I2C_SR2_RESET_UMASK			(0x40)
+#define I2C_SR2_MASK				(0xBF)
+#define I2C_SR2_SCLFAL_IND			(0x80)
+#define I2C_SR2_ENDAD_IND			(0x20)
+#define I2C_SR2_AF_IND				(0x10)
+#define I2C_SR2_STOPF_IND			(0x08)
+#define I2C_SR2_ARLO_IND			(0x04)
+#define I2C_SR2_BERR_IND			(0x02)
+#define I2C_SR2_DDC2BF_IND			(0x01)
+/* CCR (Clock Control Register) 8bit (R/W) */
+#define I2C_CCR					(0x0000000C)
+#define I2C_CCR_RESET_VALUE			(0x00)
+#define I2C_CCR_RESET_UMASK			(0x00)
+#define I2C_CCR_MASK				(0xFF)
+#define I2C_CCR_FMSM				(0x80)
+#define I2C_CCR_CC_MASK				(0x7F)
+/* OAR1 (Own Address Register 1) 8bit (R/W) */
+#define I2C_OAR1				(0x00000010)
+#define I2C_OAR1_RESET_VALUE			(0x00)
+#define I2C_OAR1_RESET_UMASK			(0x00)
+#define I2C_OAR1_ADD_MASK			(0xFF)
+/* OAR2 (Own Address Register 2) 8bit (R/W) */
+#define I2C_OAR2				(0x00000014)
+#define I2C_OAR2_RESET_VALUE			(0x40)
+#define I2C_OAR2_RESET_UMASK			(0x19)
+#define I2C_OAR2_MASK				(0xE6)
+#define I2C_OAR2_FR_25_10MHZ			(0x00)
+#define I2C_OAR2_FR_10_1667MHZ			(0x20)
+#define I2C_OAR2_FR_1667_2667MHZ		(0x40)
+#define I2C_OAR2_FR_2667_40MHZ			(0x60)
+#define I2C_OAR2_FR_40_5333MHZ			(0x80)
+#define I2C_OAR2_FR_5333_66MHZ			(0xA0)
+#define I2C_OAR2_FR_66_80MHZ			(0xC0)
+#define I2C_OAR2_FR_80_100MHZ			(0xE0)
+#define I2C_OAR2_FR_MASK			(0xE0)
+#define I2C_OAR2_ADD_MASK			(0x06)
+/* DR (Data Register) 8bit (R/W) */
+#define I2C_DR					(0x00000018)
+#define I2C_DR_RESET_VALUE			(0x00)
+#define I2C_DR_RESET_UMASK			(0xFF)
+#define I2C_DR_D_MASK				(0xFF)
+/* ECCR (Extended Clock Control Register) 8bit (R/W) */
+#define I2C_ECCR				(0x0000001C)
+#define I2C_ECCR_RESET_VALUE			(0x00)
+#define I2C_ECCR_RESET_UMASK			(0xE0)
+#define I2C_ECCR_MASK				(0x1F)
+#define I2C_ECCR_CC_MASK			(0x1F)
+
+/*
+ * These events are more or less responses to commands
+ * sent into the hardware, presumably reflecting the state
+ * of an internal state machine.
+ */
+enum stu300_event {
+	STU300_EVENT_NONE = 0,
+	STU300_EVENT_1,
+	STU300_EVENT_2,
+	STU300_EVENT_3,
+	STU300_EVENT_4,
+	STU300_EVENT_5,
+	STU300_EVENT_6,
+	STU300_EVENT_7,
+	STU300_EVENT_8,
+	STU300_EVENT_9
+};
+
+enum stu300_error {
+	STU300_ERROR_NONE = 0,
+	STU300_ERROR_ACKNOWLEDGE_FAILURE,
+	STU300_ERROR_BUS_ERROR,
+	STU300_ERROR_ARBITRATION_LOST
+};
+
+/* timeout waiting for the controller to respond */
+#define STU300_TIMEOUT (msecs_to_jiffies(1000))
+
+/*
+ * The number of address send athemps tried before giving up.
+ * If the first one failes it seems like 5 to 8 attempts are required.
+ */
+#define NUM_ADDR_RESEND_ATTEMPTS 10
+
+/* I2C clock speed, in Hz 0-400kHz*/
+static unsigned int scl_frequency = 100000;
+module_param(scl_frequency, uint,  0644);
+
+/**
+ * struct stu300_dev - the stu300 driver state holder
+ * @pdev: parent platform device
+ * @adapter: corresponding I2C adapter
+ * @phybase: location of I/O area in memory
+ * @physize: size of I/O area in memory
+ * @clk: hardware block clock
+ * @irq: assigned interrupt line
+ * @cmd_issue_lock: this locks the following cmd_ variables
+ * @cmd_complete: acknowledge completion for an I2C command
+ * @cmd_event: expected event coming in as a response to a command
+ * @cmd_err: error code as response to a command
+ * @speed: current bus speed in Hz
+ * @msg_index: index of current message
+ * @msg_len: length of current message
+ */
+struct stu300_dev {
+	struct platform_device	*pdev;
+	struct i2c_adapter	adapter;
+	resource_size_t		phybase;
+	resource_size_t		physize;
+	void __iomem		*virtbase;
+	struct clk		*clk;
+	int			irq;
+	spinlock_t		cmd_issue_lock;
+	struct completion	cmd_complete;
+	enum stu300_event	cmd_event;
+	enum stu300_error	cmd_err;
+	unsigned int		speed;
+	int			msg_index;
+	int			msg_len;
+};
+
+/* Local forward function declarations */
+static int stu300_init_hw(struct stu300_dev *dev);
+
+/*
+ * The block needs writes in both MSW and LSW in order
+ * for all data lines to reach their destination.
+ */
+static inline void stu300_wr8(u32 value, void __iomem *address)
+{
+	writel((value << 16) | value, address);
+}
+
+/*
+ * This merely masks off the duplicates which appear
+ * in bytes 1-3. You _MUST_ use 32-bit bus access on this
+ * device, else it will not work.
+ */
+static inline u32 stu300_r8(void __iomem *address)
+{
+	return readl(address) & 0x000000FFU;
+}
+
+/*
+ * Tells whether a certain event or events occurred in
+ * response to a command. The events represent states in
+ * the internal state machine of the hardware. The events
+ * are not very well described in the hardware
+ * documentation and can only be treated as abstract state
+ * machine states.
+ *
+ * @ret 0 = event has not occurred, any other value means
+ * the event occurred.
+ */
+static int stu300_event_occurred(struct stu300_dev *dev,
+				   enum stu300_event mr_event) {
+	u32 status1;
+	u32 status2;
+
+	/* What event happened? */
+	status1 = stu300_r8(dev->virtbase + I2C_SR1);
+	if (!(status1 & I2C_SR1_EVF_IND))
+		/* No event at all */
+		return 0;
+	status2 = stu300_r8(dev->virtbase + I2C_SR2);
+
+	switch (mr_event) {
+	case STU300_EVENT_1:
+		if (status1 & I2C_SR1_ADSL_IND)
+			return 1;
+		break;
+	case STU300_EVENT_2:
+	case STU300_EVENT_3:
+	case STU300_EVENT_7:
+	case STU300_EVENT_8:
+		if (status1 & I2C_SR1_BTF_IND) {
+			if (status2 & I2C_SR2_AF_IND)
+				dev->cmd_err = STU300_ERROR_ACKNOWLEDGE_FAILURE;
+			else if (status2 & I2C_SR2_BERR_IND)
+				dev->cmd_err = STU300_ERROR_BUS_ERROR;
+			return 1;
+		}
+		break;
+	case STU300_EVENT_4:
+		if (status2 & I2C_SR2_STOPF_IND)
+			return 1;
+		break;
+	case STU300_EVENT_5:
+		if (status1 & I2C_SR1_SB_IND)
+			/* Clear start bit */
+			return 1;
+		break;
+	case STU300_EVENT_6:
+		if (status2 & I2C_SR2_ENDAD_IND) {
+			/* First check for any errors */
+			if (status2 & I2C_SR2_AF_IND)
+				dev->cmd_err = STU300_ERROR_ACKNOWLEDGE_FAILURE;
+			return 1;
+		}
+		break;
+	case STU300_EVENT_9:
+		if (status1 & I2C_SR1_ADD10_IND)
+			return 1;
+		break;
+	default:
+		break;
+	}
+	if (status2 & I2C_SR2_ARLO_IND)
+		dev->cmd_err = STU300_ERROR_ARBITRATION_LOST;
+	return 0;
+}
+
+static irqreturn_t stu300_irh(int irq, void *data)
+{
+	struct stu300_dev *dev = data;
+	int res;
+
+	/* See if this was what we were waiting for */
+	spin_lock(&dev->cmd_issue_lock);
+	if (dev->cmd_event != STU300_EVENT_NONE) {
+		res = stu300_event_occurred(dev, dev->cmd_event);
+		if (res || dev->cmd_err != STU300_ERROR_NONE) {
+			u32 val;
+
+			complete(&dev->cmd_complete);
+			/* Block any multiple interrupts */
+			val = stu300_r8(dev->virtbase + I2C_CR);
+			val &= ~I2C_CR_INTERRUPT_ENABLE;
+			stu300_wr8(val, dev->virtbase + I2C_CR);
+		}
+	}
+	spin_unlock(&dev->cmd_issue_lock);
+	return IRQ_HANDLED;
+}
+
+/*
+ * Sends a command and then waits for the bits masked by *flagmask*
+ * to go high or low by IRQ awaiting.
+ */
+static int stu300_start_and_await_event(struct stu300_dev *dev,
+					  u8 cr_value,
+					  enum stu300_event mr_event)
+{
+	int ret;
+
+	if (unlikely(irqs_disabled())) {
+		/* TODO: implement polling for this case if need be. */
+		WARN(1, "irqs are disabled, cannot poll for event\n");
+		return -EIO;
+	}
+
+	/* Lock command issue, fill in an event we wait for */
+	spin_lock_irq(&dev->cmd_issue_lock);
+	init_completion(&dev->cmd_complete);
+	dev->cmd_err = STU300_ERROR_NONE;
+	dev->cmd_event = mr_event;
+	spin_unlock_irq(&dev->cmd_issue_lock);
+
+	/* Turn on interrupt, send command and wait. */
+	cr_value |= I2C_CR_INTERRUPT_ENABLE;
+	stu300_wr8(cr_value, dev->virtbase + I2C_CR);
+	ret = wait_for_completion_interruptible_timeout(&dev->cmd_complete,
+							STU300_TIMEOUT);
+
+	if (ret < 0) {
+		dev_err(&dev->pdev->dev,
+		       "wait_for_completion_interruptible_timeout() "
+		       "returned %d waiting for event %04x\n", ret, mr_event);
+		return ret;
+	}
+
+	if (ret == 0) {
+		dev_err(&dev->pdev->dev, "controller timed out "
+		       "waiting for event %d, reinit hardware\n", mr_event);
+		(void) stu300_init_hw(dev);
+		return -ETIMEDOUT;
+	}
+
+	if (dev->cmd_err != STU300_ERROR_NONE) {
+		dev_err(&dev->pdev->dev, "controller (start) "
+		       "error %d waiting for event %d, reinit hardware\n",
+		       dev->cmd_err, mr_event);
+		(void) stu300_init_hw(dev);
+		return -EIO;
+	}
+
+	return 0;
+}
+
+/*
+ * This waits for a flag to be set, if it is not set on entry, an interrupt is
+ * configured to wait for the flag using a completion.
+ */
+static int stu300_await_event(struct stu300_dev *dev,
+				enum stu300_event mr_event)
+{
+	int ret;
+	u32 val;
+
+	if (unlikely(irqs_disabled())) {
+		/* TODO: implement polling for this case if need be. */
+		dev_err(&dev->pdev->dev, "irqs are disabled on this "
+			"system!\n");
+		return -EIO;
+	}
+
+	/* Is it already here? */
+	spin_lock_irq(&dev->cmd_issue_lock);
+	dev->cmd_err = STU300_ERROR_NONE;
+	if (stu300_event_occurred(dev, mr_event)) {
+		spin_unlock_irq(&dev->cmd_issue_lock);
+		goto exit_await_check_err;
+	}
+	init_completion(&dev->cmd_complete);
+	dev->cmd_err = STU300_ERROR_NONE;
+	dev->cmd_event = mr_event;
+
+	/* Turn on the I2C interrupt for current operation */
+	val = stu300_r8(dev->virtbase + I2C_CR);
+	val |= I2C_CR_INTERRUPT_ENABLE;
+	stu300_wr8(val, dev->virtbase + I2C_CR);
+
+	/* Twice paranoia (possible HW glitch) */
+	stu300_wr8(val, dev->virtbase + I2C_CR);
+
+	/* Check again: is it already here? */
+	if (unlikely(stu300_event_occurred(dev, mr_event))) {
+		/* Disable IRQ again. */
+		val &= ~I2C_CR_INTERRUPT_ENABLE;
+		stu300_wr8(val, dev->virtbase + I2C_CR);
+		spin_unlock_irq(&dev->cmd_issue_lock);
+		goto exit_await_check_err;
+	}
+
+	/* Unlock the command block and wait for the event to occur */
+	spin_unlock_irq(&dev->cmd_issue_lock);
+	ret = wait_for_completion_interruptible_timeout(&dev->cmd_complete,
+							STU300_TIMEOUT);
+
+	if (ret < 0) {
+		dev_err(&dev->pdev->dev,
+		       "wait_for_completion_interruptible_timeout()"
+		       "returned %d waiting for event %04x\n", ret, mr_event);
+		return ret;
+	}
+
+	if (ret == 0) {
+		if (mr_event != STU300_EVENT_6) {
+			dev_err(&dev->pdev->dev, "controller "
+				"timed out waiting for event %d, reinit "
+				"hardware\n", mr_event);
+			(void) stu300_init_hw(dev);
+		}
+		return -ETIMEDOUT;
+	}
+
+ exit_await_check_err:
+	if (dev->cmd_err != STU300_ERROR_NONE) {
+		if (mr_event != STU300_EVENT_6) {
+			dev_err(&dev->pdev->dev, "controller "
+				"error (await_event) %d waiting for event %d, "
+			       "reinit hardware\n", dev->cmd_err, mr_event);
+			(void) stu300_init_hw(dev);
+		}
+		return -EIO;
+	}
+
+	return 0;
+}
+
+/*
+ * Waits for the busy bit to go low by repeated polling.
+ */
+#define BUSY_RELEASE_ATTEMPTS 10
+static int stu300_wait_while_busy(struct stu300_dev *dev)
+{
+	unsigned long timeout;
+	int i;
+
+	for (i = 0; i < BUSY_RELEASE_ATTEMPTS; i++) {
+		timeout = jiffies + STU300_TIMEOUT;
+
+		while (!time_after(jiffies, timeout)) {
+			/* Is not busy? */
+			if ((stu300_r8(dev->virtbase + I2C_SR1) &
+			     I2C_SR1_BUSY_IND) == 0)
+				return 0;
+			msleep(1);
+		}
+
+		dev_err(&dev->pdev->dev, "transaction timed out "
+			"waiting for device to be free (not busy). "
+		       "Attempt: %d\n", i+1);
+
+		dev_err(&dev->pdev->dev, "base address = "
+			"0x%08x, reinit hardware\n", (u32) dev->virtbase);
+
+		(void) stu300_init_hw(dev);
+	}
+
+	dev_err(&dev->pdev->dev, "giving up after %d attempts "
+		"to reset the bus.\n",  BUSY_RELEASE_ATTEMPTS);
+
+	return -ETIMEDOUT;
+}
+
+struct stu300_clkset {
+	unsigned long rate;
+	u32 setting;
+};
+
+static const struct stu300_clkset stu300_clktable[] = {
+	{ 0, 0xFFU },
+	{ 2500000, I2C_OAR2_FR_25_10MHZ },
+	{ 10000000, I2C_OAR2_FR_10_1667MHZ },
+	{ 16670000, I2C_OAR2_FR_1667_2667MHZ },
+	{ 26670000, I2C_OAR2_FR_2667_40MHZ },
+	{ 40000000, I2C_OAR2_FR_40_5333MHZ },
+	{ 53330000, I2C_OAR2_FR_5333_66MHZ },
+	{ 66000000, I2C_OAR2_FR_66_80MHZ },
+	{ 80000000, I2C_OAR2_FR_80_100MHZ },
+	{ 100000000, 0xFFU },
+};
+
+static int stu300_set_clk(struct stu300_dev *dev, unsigned long clkrate)
+{
+
+	u32 val;
+	int i = 0;
+
+	/* Locate the apropriate clock setting */
+	while (i < ARRAY_SIZE(stu300_clktable) &&
+	       stu300_clktable[i].rate < clkrate)
+		i++;
+
+	if (stu300_clktable[i].setting == 0xFFU) {
+		dev_err(&dev->pdev->dev, "too %s clock rate requested "
+			"(%lu Hz).\n", i ? "high" : "low", clkrate);
+		return -EINVAL;
+	}
+
+	stu300_wr8(stu300_clktable[i].setting,
+		   dev->virtbase + I2C_OAR2);
+
+	dev_dbg(&dev->pdev->dev, "Clock rate %lu Hz, I2C bus speed %d Hz "
+		"virtbase %p\n", clkrate, dev->speed, dev->virtbase);
+
+	if (dev->speed > 100000)
+		/* Fast Mode I2C */
+		val = ((clkrate/dev->speed)-9)/3;
+	else
+		/* Standard Mode I2C */
+		val = ((clkrate/dev->speed)-7)/2;
+
+	/* According to spec the divider must be > 2 */
+	if (val < 0x002) {
+		dev_err(&dev->pdev->dev, "too low clock rate (%lu Hz).\n",
+			clkrate);
+		return -EINVAL;
+	}
+
+	/* We have 12 bits clock divider only! */
+	if (val & 0xFFFFF000U) {
+		dev_err(&dev->pdev->dev, "too high clock rate (%lu Hz).\n",
+			clkrate);
+		return -EINVAL;
+	}
+
+	if (dev->speed > 100000) {
+		/* CC6..CC0 */
+		stu300_wr8((val & I2C_CCR_CC_MASK) | I2C_CCR_FMSM,
+			   dev->virtbase + I2C_CCR);
+		dev_dbg(&dev->pdev->dev, "set clock divider to 0x%08x, "
+			"Fast Mode I2C\n", val);
+	} else {
+		/* CC6..CC0 */
+		stu300_wr8((val & I2C_CCR_CC_MASK),
+			   dev->virtbase + I2C_CCR);
+		dev_dbg(&dev->pdev->dev, "set clock divider to "
+			"0x%08x, Standard Mode I2C\n", val);
+	}
+
+	/* CC11..CC7 */
+	stu300_wr8(((val >> 7) & 0x1F),
+		   dev->virtbase + I2C_ECCR);
+
+	return 0;
+}
+
+
+static int stu300_init_hw(struct stu300_dev *dev)
+{
+	u32 dummy;
+	unsigned long clkrate;
+	int ret;
+
+	/* Disable controller */
+	stu300_wr8(0x00, dev->virtbase + I2C_CR);
+	/*
+	 * Set own address to some default value (0x00).
+	 * We do not support slave mode anyway.
+	 */
+	stu300_wr8(0x00, dev->virtbase + I2C_OAR1);
+	/*
+	 * The I2C controller only operates properly in 26 MHz but we
+	 * program this driver as if we didn't know. This will also set the two
+	 * high bits of the own address to zero as well.
+	 * There is no known hardware issue with running in 13 MHz
+	 * However, speeds over 200 kHz are not used.
+	 */
+	clkrate = clk_get_rate(dev->clk);
+	ret = stu300_set_clk(dev, clkrate);
+	if (ret)
+		return ret;
+	/*
+	 * Enable block, do it TWICE (hardware glitch)
+	 * Setting bit 7 can enable DDC mode. (Not used currently.)
+	 */
+	stu300_wr8(I2C_CR_PERIPHERAL_ENABLE,
+				  dev->virtbase + I2C_CR);
+	stu300_wr8(I2C_CR_PERIPHERAL_ENABLE,
+				  dev->virtbase + I2C_CR);
+	/* Make a dummy read of the status register SR1 & SR2 */
+	dummy = stu300_r8(dev->virtbase + I2C_SR2);
+	dummy = stu300_r8(dev->virtbase + I2C_SR1);
+
+	return 0;
+}
+
+
+
+/* Send slave address. */
+static int stu300_send_address(struct stu300_dev *dev,
+				 struct i2c_msg *msg, int resend)
+{
+	u32 val;
+	int ret;
+
+	if (msg->flags & I2C_M_TEN)
+		/* This is probably how 10 bit addresses look */
+		val = (0xf0 | (((u32) msg->addr & 0x300) >> 7)) &
+			I2C_DR_D_MASK;
+	else
+		val = ((msg->addr << 1) & I2C_DR_D_MASK);
+
+	if (msg->flags & I2C_M_RD) {
+		/* This is the direction bit */
+		val |= 0x01;
+		if (resend)
+			dev_dbg(&dev->pdev->dev, "read resend\n");
+	} else if (resend)
+		dev_dbg(&dev->pdev->dev, "write resend\n");
+	stu300_wr8(val, dev->virtbase + I2C_DR);
+
+	/* For 10bit addressing, await 10bit request (EVENT 9) */
+	if (msg->flags & I2C_M_TEN) {
+		ret = stu300_await_event(dev, STU300_EVENT_9);
+		/*
+		 * The slave device wants a 10bit address, send the rest
+		 * of the bits (the LSBits)
+		 */
+		val = msg->addr & I2C_DR_D_MASK;
+		/* This clears "event 9" */
+		stu300_wr8(val, dev->virtbase + I2C_DR);
+		if (ret != 0)
+			return ret;
+	}
+	/* FIXME: Why no else here? two events for 10bit?
+	 * Await event 6 (normal) or event 9 (10bit)
+	 */
+
+	if (resend)
+		dev_dbg(&dev->pdev->dev, "await event 6\n");
+	ret = stu300_await_event(dev, STU300_EVENT_6);
+
+	/*
+	 * Clear any pending EVENT 6 no matter what happend during
+	 * await_event.
+	 */
+	val = stu300_r8(dev->virtbase + I2C_CR);
+	val |= I2C_CR_PERIPHERAL_ENABLE;
+	stu300_wr8(val, dev->virtbase + I2C_CR);
+
+	return ret;
+}
+
+static int stu300_xfer_msg(struct i2c_adapter *adap,
+			     struct i2c_msg *msg, int stop)
+{
+	u32 cr;
+	u32 val;
+	u32 i;
+	int ret;
+	int attempts = 0;
+	struct stu300_dev *dev = i2c_get_adapdata(adap);
+
+
+	clk_enable(dev->clk);
+
+	/* Remove this if (0) to trace each and every message. */
+	if (0) {
+		dev_dbg(&dev->pdev->dev, "I2C message to: 0x%04x, len: %d, "
+			"flags: 0x%04x, stop: %d\n",
+			msg->addr, msg->len, msg->flags, stop);
+	}
+
+	/* Zero-length messages are not supported by this hardware */
+	if (msg->len == 0) {
+		ret = -EINVAL;
+		goto exit_disable;
+	}
+
+	/*
+	 * For some reason, sending the address sometimes fails when running
+	 * on  the 13 MHz clock. No interrupt arrives. This is a work around,
+	 * which tries to restart and send the address up to 10 times before
+	 * really giving up. Usually 5 to 8 attempts are enough.
+	 */
+	do {
+		if (attempts)
+			dev_dbg(&dev->pdev->dev, "wait while busy\n");
+		/* Check that the bus is free, or wait until some timeout */
+		ret = stu300_wait_while_busy(dev);
+		if (ret != 0)
+			goto exit_disable;
+
+		if (attempts)
+			dev_dbg(&dev->pdev->dev, "re-int hw\n");
+		/*
+		 * According to ST, there is no problem if the clock is
+		 * changed between 13 and 26 MHz during a transfer.
+		 */
+		ret = stu300_init_hw(dev);
+		if (ret)
+			goto exit_disable;
+
+		/* Send a start condition */
+		cr = I2C_CR_PERIPHERAL_ENABLE;
+		/* Setting the START bit puts the block in master mode */
+		if (!(msg->flags & I2C_M_NOSTART))
+			cr |= I2C_CR_START_ENABLE;
+		if ((msg->flags & I2C_M_RD) && (msg->len > 1))
+			/* On read more than 1 byte, we need ack. */
+			cr |= I2C_CR_ACK_ENABLE;
+		/* Check that it gets through */
+		if (!(msg->flags & I2C_M_NOSTART)) {
+			if (attempts)
+				dev_dbg(&dev->pdev->dev, "send start event\n");
+			ret = stu300_start_and_await_event(dev, cr,
+							     STU300_EVENT_5);
+		}
+
+		if (attempts)
+			dev_dbg(&dev->pdev->dev, "send address\n");
+
+		if (ret == 0)
+			/* Send address */
+			ret = stu300_send_address(dev, msg, attempts != 0);
+
+		if (ret != 0) {
+			attempts++;
+			dev_dbg(&dev->pdev->dev, "failed sending address, "
+				"retrying. Attempt: %d msg_index: %d/%d\n",
+			       attempts, dev->msg_index, dev->msg_len);
+		}
+
+	} while (ret != 0 && attempts < NUM_ADDR_RESEND_ATTEMPTS);
+
+	if (attempts < NUM_ADDR_RESEND_ATTEMPTS && attempts > 0) {
+		dev_dbg(&dev->pdev->dev, "managed to get address "
+		       "through after %d attempts\n", attempts);
+	} else if (attempts == NUM_ADDR_RESEND_ATTEMPTS) {
+		dev_dbg(&dev->pdev->dev, "I give up, tried %d times "
+		       "to resend address.\n",
+		       NUM_ADDR_RESEND_ATTEMPTS);
+		goto exit_disable;
+	}
+
+	if (msg->flags & I2C_M_RD) {
+		/* READ: we read the actual bytes one at a time */
+		for (i = 0; i < msg->len; i++) {
+			if (i == msg->len-1) {
+				/*
+				 * Disable ACK and set STOP condition before
+				 * reading last byte
+				 */
+				val = I2C_CR_PERIPHERAL_ENABLE;
+
+				if (stop)
+					val |= I2C_CR_STOP_ENABLE;
+
+				stu300_wr8(val,
+					   dev->virtbase + I2C_CR);
+			}
+			/* Wait for this byte... */
+			ret = stu300_await_event(dev, STU300_EVENT_7);
+			if (ret != 0)
+				goto exit_disable;
+			/* This clears event 7 */
+			msg->buf[i] = (u8) stu300_r8(dev->virtbase + I2C_DR);
+		}
+	} else {
+		/* WRITE: we send the actual bytes one at a time */
+		for (i = 0; i < msg->len; i++) {
+			/* Write the byte */
+			stu300_wr8(msg->buf[i],
+				   dev->virtbase + I2C_DR);
+			/* Check status */
+			ret = stu300_await_event(dev, STU300_EVENT_8);
+			/* Next write to DR will clear event 8 */
+			if (ret != 0) {
+				dev_err(&dev->pdev->dev, "error awaiting "
+				       "event 8 (%d)\n", ret);
+				goto exit_disable;
+			}
+		}
+		/* Check NAK */
+		if (!(msg->flags & I2C_M_IGNORE_NAK)) {
+			if (stu300_r8(dev->virtbase + I2C_SR2) &
+			    I2C_SR2_AF_IND) {
+				dev_err(&dev->pdev->dev, "I2C payload "
+				       "send returned NAK!\n");
+				ret = -EIO;
+				goto exit_disable;
+			}
+		}
+		if (stop) {
+			/* Send stop condition */
+			val = I2C_CR_PERIPHERAL_ENABLE;
+			val |= I2C_CR_STOP_ENABLE;
+			stu300_wr8(val, dev->virtbase + I2C_CR);
+		}
+	}
+
+	/* Check that the bus is free, or wait until some timeout occurs */
+	ret = stu300_wait_while_busy(dev);
+	if (ret != 0) {
+		dev_err(&dev->pdev->dev, "timout waiting for transfer "
+		       "to commence.\n");
+		goto exit_disable;
+	}
+
+	/* Dummy read status registers */
+	val = stu300_r8(dev->virtbase + I2C_SR2);
+	val = stu300_r8(dev->virtbase + I2C_SR1);
+	ret = 0;
+
+ exit_disable:
+	/* Disable controller */
+	stu300_wr8(0x00, dev->virtbase + I2C_CR);
+	clk_disable(dev->clk);
+	return ret;
+}
+
+static int stu300_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
+			 int num)
+{
+	int ret = -1;
+	int i;
+	struct stu300_dev *dev = i2c_get_adapdata(adap);
+	dev->msg_len = num;
+	for (i = 0; i < num; i++) {
+		/*
+		 * Another driver appears to send stop for each message,
+		 * here we only do that for the last message. Possibly some
+		 * peripherals require this behaviour, then their drivers
+		 * have to send single messages in order to get "stop" for
+		 * each message.
+		 */
+		dev->msg_index = i;
+
+		ret = stu300_xfer_msg(adap, &msgs[i], (i == (num - 1)));
+		if (ret != 0) {
+			num = ret;
+			break;
+		}
+	}
+
+	return num;
+}
+
+static u32 stu300_func(struct i2c_adapter *adap)
+{
+	/* This is the simplest thing you can think of... */
+	return I2C_FUNC_I2C | I2C_FUNC_10BIT_ADDR;
+}
+
+static const struct i2c_algorithm stu300_algo = {
+	.master_xfer	= stu300_xfer,
+	.functionality	= stu300_func,
+};
+
+static int __init
+stu300_probe(struct platform_device *pdev)
+{
+	struct stu300_dev *dev;
+	struct i2c_adapter *adap;
+	struct resource *res;
+	int bus_nr;
+	int ret = 0;
+
+	dev = kzalloc(sizeof(struct stu300_dev), GFP_KERNEL);
+	if (!dev) {
+		dev_err(&pdev->dev, "could not allocate device struct\n");
+		ret = -ENOMEM;
+		goto err_no_devmem;
+	}
+
+	bus_nr = pdev->id;
+	dev->clk = clk_get(&pdev->dev, NULL);
+	if (IS_ERR(dev->clk)) {
+		ret = PTR_ERR(dev->clk);
+		dev_err(&pdev->dev, "could not retrieve i2c bus clock\n");
+		goto err_no_clk;
+	}
+
+	dev->pdev = pdev;
+	platform_set_drvdata(pdev, dev);
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	if (!res) {
+		ret = -ENOENT;
+		goto err_no_resource;
+	}
+
+	dev->phybase = res->start;
+	dev->physize = resource_size(res);
+
+	if (request_mem_region(dev->phybase, dev->physize,
+			       NAME " I/O Area") == NULL) {
+		ret = -EBUSY;
+		goto err_no_ioregion;
+	}
+
+	dev->virtbase = ioremap(dev->phybase, dev->physize);
+	dev_dbg(&pdev->dev, "initialize bus device I2C%d on virtual "
+		"base %p\n", bus_nr, dev->virtbase);
+	if (!dev->virtbase) {
+		ret = -ENOMEM;
+		goto err_no_ioremap;
+	}
+
+	dev->irq = platform_get_irq(pdev, 0);
+	if (request_irq(dev->irq, stu300_irh, IRQF_DISABLED,
+			NAME, dev)) {
+		ret = -EIO;
+		goto err_no_irq;
+	}
+
+	dev->speed = scl_frequency;
+
+	clk_enable(dev->clk);
+	ret = stu300_init_hw(dev);
+	clk_disable(dev->clk);
+
+	if (ret != 0) {
+		dev_err(&dev->pdev->dev, "error initializing hardware.\n");
+		goto err_init_hw;
+	}
+
+	/* IRQ event handling initialization */
+	spin_lock_init(&dev->cmd_issue_lock);
+	dev->cmd_event = STU300_EVENT_NONE;
+	dev->cmd_err = STU300_ERROR_NONE;
+
+	adap = &dev->adapter;
+	adap->owner = THIS_MODULE;
+	/* DDC class but actually often used for more generic I2C */
+	adap->class = I2C_CLASS_DDC;
+	strncpy(adap->name, "ST Microelectronics DDC I2C adapter",
+		sizeof(adap->name));
+	adap->nr = bus_nr;
+	adap->algo = &stu300_algo;
+	adap->dev.parent = &pdev->dev;
+	i2c_set_adapdata(adap, dev);
+
+	/* i2c device drivers may be active on return from add_adapter() */
+	ret = i2c_add_numbered_adapter(adap);
+	if (ret) {
+		dev_err(&dev->pdev->dev, "failure adding ST Micro DDC "
+		       "I2C adapter\n");
+		goto err_add_adapter;
+	}
+	return 0;
+
+ err_add_adapter:
+ err_init_hw:
+	free_irq(dev->irq, dev);
+ err_no_irq:
+	iounmap(dev->virtbase);
+ err_no_ioremap:
+	release_mem_region(dev->phybase, dev->physize);
+ err_no_ioregion:
+	platform_set_drvdata(pdev, NULL);
+ err_no_resource:
+	clk_put(dev->clk);
+ err_no_clk:
+	kfree(dev);
+ err_no_devmem:
+	dev_err(&pdev->dev, "failed to add " NAME " adapter: %d\n",
+		pdev->id);
+	return ret;
+}
+
+#ifdef CONFIG_PM
+static int stu300_suspend(struct platform_device *pdev, pm_message_t state)
+{
+	struct stu300_dev *dev = platform_get_drvdata(pdev);
+
+	/* Turn off everything */
+	stu300_wr8(0x00, dev->virtbase + I2C_CR);
+	return 0;
+}
+
+static int stu300_resume(struct platform_device *pdev)
+{
+	int ret = 0;
+	struct stu300_dev *dev = platform_get_drvdata(pdev);
+
+	clk_enable(dev->clk);
+	ret = stu300_init_hw(dev);
+	clk_disable(dev->clk);
+
+	if (ret != 0)
+		dev_err(&pdev->dev, "error re-initializing hardware.\n");
+	return ret;
+}
+#else
+#define stu300_suspend NULL
+#define stu300_resume NULL
+#endif
+
+static int __exit
+stu300_remove(struct platform_device *pdev)
+{
+	struct stu300_dev *dev = platform_get_drvdata(pdev);
+
+	i2c_del_adapter(&dev->adapter);
+	/* Turn off everything */
+	stu300_wr8(0x00, dev->virtbase + I2C_CR);
+	free_irq(dev->irq, dev);
+	iounmap(dev->virtbase);
+	release_mem_region(dev->phybase, dev->physize);
+	clk_put(dev->clk);
+	platform_set_drvdata(pdev, NULL);
+	kfree(dev);
+	return 0;
+}
+
+static struct platform_driver stu300_i2c_driver = {
+	.driver = {
+		.name	= NAME,
+		.owner	= THIS_MODULE,
+	},
+	.remove		= __exit_p(stu300_remove),
+	.suspend        = stu300_suspend,
+	.resume         = stu300_resume,
+
+};
+
+static int __init stu300_init(void)
+{
+	return platform_driver_probe(&stu300_i2c_driver, stu300_probe);
+}
+
+static void __exit stu300_exit(void)
+{
+	platform_driver_unregister(&stu300_i2c_driver);
+}
+
+/*
+ * The systems using this bus often have very basic devices such
+ * as regulators on the I2C bus, so this needs to be loaded early.
+ * Therefore it is registered in the subsys_initcall().
+ */
+subsys_initcall(stu300_init);
+module_exit(stu300_exit);
+
+MODULE_AUTHOR("Linus Walleij <linus.walleij@stericsson.com>");
+MODULE_DESCRIPTION("ST Micro DDC I2C adapter (" NAME ")");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("platform:" NAME);