drivers/i2c/busses/i2c-emev2.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * I2C driver for the Renesas EMEV2 SoC
  *
  * Copyright (C) 2015 Wolfram Sang <wsa@sang-engineering.com>
  * Copyright 2013 Codethink Ltd.
  * Copyright 2010-2015 Renesas Electronics Corporation
  */

 #include <linux/clk.h>
 #include <linux/completion.h>
 #include <linux/device.h>
 #include <linux/i2c.h>
 #include <linux/init.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/platform_device.h>
 #include <linux/sched.h>

 /* I2C Registers */
 #define I2C_OFS_IICACT0		0x00	/* start */
 #define I2C_OFS_IIC0		0x04	/* shift */
 #define I2C_OFS_IICC0		0x08	/* control */
 #define I2C_OFS_SVA0		0x0c	/* slave address */
 #define I2C_OFS_IICCL0		0x10	/* clock select */
 #define I2C_OFS_IICX0		0x14	/* extension */
 #define I2C_OFS_IICS0		0x18	/* status */
 #define I2C_OFS_IICSE0		0x1c	/* status For emulation */
 #define I2C_OFS_IICF0		0x20	/* IIC flag */

 /* I2C IICACT0 Masks */
 #define I2C_BIT_IICE0		0x0001

 /* I2C IICC0 Masks */
 #define I2C_BIT_LREL0		0x0040
 #define I2C_BIT_WREL0		0x0020
 #define I2C_BIT_SPIE0		0x0010
 #define I2C_BIT_WTIM0		0x0008
 #define I2C_BIT_ACKE0		0x0004
 #define I2C_BIT_STT0		0x0002
 #define I2C_BIT_SPT0		0x0001

 /* I2C IICCL0 Masks */
 #define I2C_BIT_SMC0		0x0008
 #define I2C_BIT_DFC0		0x0004

 /* I2C IICSE0 Masks */
 #define I2C_BIT_MSTS0		0x0080
 #define I2C_BIT_ALD0		0x0040
 #define I2C_BIT_EXC0		0x0020
 #define I2C_BIT_COI0		0x0010
 #define I2C_BIT_TRC0		0x0008
 #define I2C_BIT_ACKD0		0x0004
 #define I2C_BIT_STD0		0x0002
 #define I2C_BIT_SPD0		0x0001

 /* I2C IICF0 Masks */
 #define I2C_BIT_STCF		0x0080
 #define I2C_BIT_IICBSY		0x0040
 #define I2C_BIT_STCEN		0x0002
 #define I2C_BIT_IICRSV		0x0001

 struct em_i2c_device {
 	void __iomem *base;
 	struct i2c_adapter adap;
 	struct completion msg_done;
 	struct clk *sclk;
 	struct i2c_client *slave;
 	int irq;
 };

 static inline void em_clear_set_bit(struct em_i2c_device *priv, u8 clear, u8 set, u8 reg)
 {
 	writeb((readb(priv->base + reg) & ~clear) | set, priv->base + reg);
 }

 static int em_i2c_wait_for_event(struct em_i2c_device *priv)
 {
 	unsigned long time_left;
 	int status;

 	reinit_completion(&priv->msg_done);

 	time_left = wait_for_completion_timeout(&priv->msg_done, priv->adap.timeout);

 	if (!time_left)
 		return -ETIMEDOUT;

 	status = readb(priv->base + I2C_OFS_IICSE0);
 	return status & I2C_BIT_ALD0 ? -EAGAIN : status;
 }

 static void em_i2c_stop(struct em_i2c_device *priv)
 {
 	/* Send Stop condition */
 	em_clear_set_bit(priv, 0, I2C_BIT_SPT0 | I2C_BIT_SPIE0, I2C_OFS_IICC0);

 	/* Wait for stop condition */
 	em_i2c_wait_for_event(priv);
 }

 static void em_i2c_reset(struct i2c_adapter *adap)
 {
 	struct em_i2c_device *priv = i2c_get_adapdata(adap);
 	int retr;

 	/* If I2C active */
 	if (readb(priv->base + I2C_OFS_IICACT0) & I2C_BIT_IICE0) {
 		/* Disable I2C operation */
 		writeb(0, priv->base + I2C_OFS_IICACT0);

 		retr = 1000;
 		while (readb(priv->base + I2C_OFS_IICACT0) == 1 && retr)
 			retr--;
 		WARN_ON(retr == 0);
 	}

 	/* Transfer mode set */
 	writeb(I2C_BIT_DFC0, priv->base + I2C_OFS_IICCL0);

 	/* Can Issue start without detecting a stop, Reservation disabled. */
 	writeb(I2C_BIT_STCEN | I2C_BIT_IICRSV, priv->base + I2C_OFS_IICF0);

 	/* I2C enable, 9 bit interrupt mode */
 	writeb(I2C_BIT_WTIM0, priv->base + I2C_OFS_IICC0);

 	/* Enable I2C operation */
 	writeb(I2C_BIT_IICE0, priv->base + I2C_OFS_IICACT0);

 	retr = 1000;
 	while (readb(priv->base + I2C_OFS_IICACT0) == 0 && retr)
 		retr--;
 	WARN_ON(retr == 0);
 }

 static int __em_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msg,
 				int stop)
 {
 	struct em_i2c_device *priv = i2c_get_adapdata(adap);
 	int count, status, read = !!(msg->flags & I2C_M_RD);

 	/* Send start condition */
 	em_clear_set_bit(priv, 0, I2C_BIT_ACKE0 | I2C_BIT_WTIM0, I2C_OFS_IICC0);
 	em_clear_set_bit(priv, 0, I2C_BIT_STT0, I2C_OFS_IICC0);

 	/* Send slave address and R/W type */
 	writeb(i2c_8bit_addr_from_msg(msg), priv->base + I2C_OFS_IIC0);

 	/* Wait for transaction */
 	status = em_i2c_wait_for_event(priv);
 	if (status < 0)
 		goto out_reset;

 	/* Received NACK (result of setting slave address and R/W) */
 	if (!(status & I2C_BIT_ACKD0)) {
 		em_i2c_stop(priv);
 		goto out;
 	}

 	/* Extra setup for read transactions */
 	if (read) {
 		/* 8 bit interrupt mode */
 		em_clear_set_bit(priv, I2C_BIT_WTIM0, I2C_BIT_ACKE0, I2C_OFS_IICC0);
 		em_clear_set_bit(priv, I2C_BIT_WTIM0, I2C_BIT_WREL0, I2C_OFS_IICC0);

 		/* Wait for transaction */
 		status = em_i2c_wait_for_event(priv);
 		if (status < 0)
 			goto out_reset;
 	}

 	/* Send / receive data */
 	for (count = 0; count < msg->len; count++) {
 		if (read) { /* Read transaction */
 			msg->buf[count] = readb(priv->base + I2C_OFS_IIC0);
 			em_clear_set_bit(priv, 0, I2C_BIT_WREL0, I2C_OFS_IICC0);

 		} else { /* Write transaction */
 			/* Received NACK */
 			if (!(status & I2C_BIT_ACKD0)) {
 				em_i2c_stop(priv);
 				goto out;
 			}

 			/* Write data */
 			writeb(msg->buf[count], priv->base + I2C_OFS_IIC0);
 		}

 		/* Wait for R/W transaction */
 		status = em_i2c_wait_for_event(priv);
 		if (status < 0)
 			goto out_reset;
 	}

 	if (stop)
 		em_i2c_stop(priv);

 	return count;

 out_reset:
 	em_i2c_reset(adap);
 out:
 	return status < 0 ? status : -ENXIO;
 }

 static int em_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
 	int num)
 {
 	struct em_i2c_device *priv = i2c_get_adapdata(adap);
 	int ret, i;

 	if (readb(priv->base + I2C_OFS_IICF0) & I2C_BIT_IICBSY)
 		return -EAGAIN;

 	for (i = 0; i < num; i++) {
 		ret = __em_i2c_xfer(adap, &msgs[i], (i == (num - 1)));
 		if (ret < 0)
 			return ret;
 	}

 	/* I2C transfer completed */
 	return num;
 }

 static bool em_i2c_slave_irq(struct em_i2c_device *priv)
 {
 	u8 status, value;
 	enum i2c_slave_event event;
 	int ret;

 	if (!priv->slave)
 		return false;

 	status = readb(priv->base + I2C_OFS_IICSE0);

 	/* Extension code, do not participate */
 	if (status & I2C_BIT_EXC0) {
 		em_clear_set_bit(priv, 0, I2C_BIT_LREL0, I2C_OFS_IICC0);
 		return true;
 	}

 	/* Stop detected, we don't know if it's for slave or master */
 	if (status & I2C_BIT_SPD0) {
 		/* Notify slave device */
 		i2c_slave_event(priv->slave, I2C_SLAVE_STOP, &value);
 		/* Pretend we did not handle the interrupt */
 		return false;
 	}

 	/* Only handle interrupts addressed to us */
 	if (!(status & I2C_BIT_COI0))
 		return false;

 	/* Enable stop interrupts */
 	em_clear_set_bit(priv, 0, I2C_BIT_SPIE0, I2C_OFS_IICC0);

 	/* Transmission or Reception */
 	if (status & I2C_BIT_TRC0) {
 		if (status & I2C_BIT_ACKD0) {
 			/* 9 bit interrupt mode */
 			em_clear_set_bit(priv, 0, I2C_BIT_WTIM0, I2C_OFS_IICC0);

 			/* Send data */
 			event = status & I2C_BIT_STD0 ?
 				I2C_SLAVE_READ_REQUESTED :
 				I2C_SLAVE_READ_PROCESSED;
 			i2c_slave_event(priv->slave, event, &value);
 			writeb(value, priv->base + I2C_OFS_IIC0);
 		} else {
 			/* NACK, stop transmitting */
 			em_clear_set_bit(priv, 0, I2C_BIT_LREL0, I2C_OFS_IICC0);
 		}
 	} else {
 		/* 8 bit interrupt mode */
 		em_clear_set_bit(priv, I2C_BIT_WTIM0, I2C_BIT_ACKE0,
 				I2C_OFS_IICC0);
 		em_clear_set_bit(priv, I2C_BIT_WTIM0, I2C_BIT_WREL0,
 				I2C_OFS_IICC0);

 		if (status & I2C_BIT_STD0) {
 			i2c_slave_event(priv->slave, I2C_SLAVE_WRITE_REQUESTED,
 					&value);
 		} else {
 			/* Recv data */
 			value = readb(priv->base + I2C_OFS_IIC0);
 			ret = i2c_slave_event(priv->slave,
 					I2C_SLAVE_WRITE_RECEIVED, &value);
 			if (ret < 0)
 				em_clear_set_bit(priv, I2C_BIT_ACKE0, 0,
 						I2C_OFS_IICC0);
 		}
 	}

 	return true;
 }

 static irqreturn_t em_i2c_irq_handler(int this_irq, void *dev_id)
 {
 	struct em_i2c_device *priv = dev_id;

 	if (em_i2c_slave_irq(priv))
 		return IRQ_HANDLED;

 	complete(&priv->msg_done);

 	return IRQ_HANDLED;
 }

 static u32 em_i2c_func(struct i2c_adapter *adap)
 {
 	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_SLAVE;
 }

 static int em_i2c_reg_slave(struct i2c_client *slave)
 {
 	struct em_i2c_device *priv = i2c_get_adapdata(slave->adapter);

 	if (priv->slave)
 		return -EBUSY;

 	if (slave->flags & I2C_CLIENT_TEN)
 		return -EAFNOSUPPORT;

 	priv->slave = slave;

 	/* Set slave address */
 	writeb(slave->addr << 1, priv->base + I2C_OFS_SVA0);

 	return 0;
 }

 static int em_i2c_unreg_slave(struct i2c_client *slave)
 {
 	struct em_i2c_device *priv = i2c_get_adapdata(slave->adapter);

 	WARN_ON(!priv->slave);

 	writeb(0, priv->base + I2C_OFS_SVA0);

 	/*
 	 * Wait for interrupt to finish. New slave irqs cannot happen because we
 	 * cleared the slave address and, thus, only extension codes will be
 	 * detected which do not use the slave ptr.
 	 */
 	synchronize_irq(priv->irq);
 	priv->slave = NULL;

 	return 0;
 }

 static const struct i2c_algorithm em_i2c_algo = {
 	.master_xfer = em_i2c_xfer,
 	.functionality = em_i2c_func,
 	.reg_slave      = em_i2c_reg_slave,
 	.unreg_slave    = em_i2c_unreg_slave,
 };

 static int em_i2c_probe(struct platform_device *pdev)
 {
 	struct em_i2c_device *priv;
 	int ret;

 	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
 	if (!priv)
 		return -ENOMEM;

 	priv->base = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(priv->base))
 		return PTR_ERR(priv->base);

 	strscpy(priv->adap.name, "EMEV2 I2C", sizeof(priv->adap.name));

 	priv->sclk = devm_clk_get(&pdev->dev, "sclk");
 	if (IS_ERR(priv->sclk))
 		return PTR_ERR(priv->sclk);

 	ret = clk_prepare_enable(priv->sclk);
 	if (ret)
 		return ret;

 	priv->adap.timeout = msecs_to_jiffies(100);
 	priv->adap.retries = 5;
 	priv->adap.dev.parent = &pdev->dev;
 	priv->adap.algo = &em_i2c_algo;
 	priv->adap.owner = THIS_MODULE;
 	priv->adap.dev.of_node = pdev->dev.of_node;

 	init_completion(&priv->msg_done);

 	platform_set_drvdata(pdev, priv);
 	i2c_set_adapdata(&priv->adap, priv);

 	em_i2c_reset(&priv->adap);

 	ret = platform_get_irq(pdev, 0);
 	if (ret < 0)
 		goto err_clk;
 	priv->irq = ret;
 	ret = devm_request_irq(&pdev->dev, priv->irq, em_i2c_irq_handler, 0,
 				"em_i2c", priv);
 	if (ret)
 		goto err_clk;

 	ret = i2c_add_adapter(&priv->adap);

 	if (ret)
 		goto err_clk;

 	dev_info(&pdev->dev, "Added i2c controller %d, irq %d\n", priv->adap.nr,
 		 priv->irq);

 	return 0;

 err_clk:
 	clk_disable_unprepare(priv->sclk);
 	return ret;
 }

 static void em_i2c_remove(struct platform_device *dev)
 {
 	struct em_i2c_device *priv = platform_get_drvdata(dev);

 	i2c_del_adapter(&priv->adap);
 	clk_disable_unprepare(priv->sclk);
 }

 static const struct of_device_id em_i2c_ids[] = {
 	{ .compatible = "renesas,iic-emev2", },
 	{ }
 };

 static struct platform_driver em_i2c_driver = {
 	.probe = em_i2c_probe,
 	.remove_new = em_i2c_remove,
 	.driver = {
 		.name = "em-i2c",
 		.of_match_table = em_i2c_ids,
 	}
 };
 module_platform_driver(em_i2c_driver);

 MODULE_DESCRIPTION("EMEV2 I2C bus driver");
 MODULE_AUTHOR("Ian Molton");
 MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");
 MODULE_LICENSE("GPL v2");
 MODULE_DEVICE_TABLE(of, em_i2c_ids);
	// SPDX-License-Identifier: GPL-2.0
	/*
	* I2C driver for the Renesas EMEV2 SoC
	*
	* Copyright (C) 2015 Wolfram Sang <wsa@sang-engineering.com>
	* Copyright 2013 Codethink Ltd.
	* Copyright 2010-2015 Renesas Electronics Corporation
	*/

	#include <linux/clk.h>
	#include <linux/completion.h>
	#include <linux/device.h>
	#include <linux/i2c.h>
	#include <linux/init.h>
	#include <linux/interrupt.h>
	#include <linux/io.h>
	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/of.h>
	#include <linux/platform_device.h>
	#include <linux/sched.h>

	/* I2C Registers */
	#define I2C_OFS_IICACT0 0x00 /* start */
	#define I2C_OFS_IIC0 0x04 /* shift */
	#define I2C_OFS_IICC0 0x08 /* control */
	#define I2C_OFS_SVA0 0x0c /* slave address */
	#define I2C_OFS_IICCL0 0x10 /* clock select */
	#define I2C_OFS_IICX0 0x14 /* extension */
	#define I2C_OFS_IICS0 0x18 /* status */
	#define I2C_OFS_IICSE0 0x1c /* status For emulation */
	#define I2C_OFS_IICF0 0x20 /* IIC flag */

	/* I2C IICACT0 Masks */
	#define I2C_BIT_IICE0 0x0001

	/* I2C IICC0 Masks */
	#define I2C_BIT_LREL0 0x0040
	#define I2C_BIT_WREL0 0x0020
	#define I2C_BIT_SPIE0 0x0010
	#define I2C_BIT_WTIM0 0x0008
	#define I2C_BIT_ACKE0 0x0004
	#define I2C_BIT_STT0 0x0002
	#define I2C_BIT_SPT0 0x0001

	/* I2C IICCL0 Masks */
	#define I2C_BIT_SMC0 0x0008
	#define I2C_BIT_DFC0 0x0004

	/* I2C IICSE0 Masks */
	#define I2C_BIT_MSTS0 0x0080
	#define I2C_BIT_ALD0 0x0040
	#define I2C_BIT_EXC0 0x0020
	#define I2C_BIT_COI0 0x0010
	#define I2C_BIT_TRC0 0x0008
	#define I2C_BIT_ACKD0 0x0004
	#define I2C_BIT_STD0 0x0002
	#define I2C_BIT_SPD0 0x0001

	/* I2C IICF0 Masks */
	#define I2C_BIT_STCF 0x0080
	#define I2C_BIT_IICBSY 0x0040
	#define I2C_BIT_STCEN 0x0002
	#define I2C_BIT_IICRSV 0x0001

	struct em_i2c_device {
	void __iomem *base;
	struct i2c_adapter adap;
	struct completion msg_done;
	struct clk *sclk;
	struct i2c_client *slave;
	int irq;
	};

	static inline void em_clear_set_bit(struct em_i2c_device *priv, u8 clear, u8 set, u8 reg)
	{
	writeb((readb(priv->base + reg) & ~clear) \| set, priv->base + reg);
	}

	static int em_i2c_wait_for_event(struct em_i2c_device *priv)
	{
	unsigned long time_left;
	int status;

	reinit_completion(&priv->msg_done);

	time_left = wait_for_completion_timeout(&priv->msg_done, priv->adap.timeout);

	if (!time_left)
	return -ETIMEDOUT;

	status = readb(priv->base + I2C_OFS_IICSE0);
	return status & I2C_BIT_ALD0 ? -EAGAIN : status;
	}

	static void em_i2c_stop(struct em_i2c_device *priv)
	{
	/* Send Stop condition */
	em_clear_set_bit(priv, 0, I2C_BIT_SPT0 \| I2C_BIT_SPIE0, I2C_OFS_IICC0);

	/* Wait for stop condition */
	em_i2c_wait_for_event(priv);
	}

	static void em_i2c_reset(struct i2c_adapter *adap)
	{
	struct em_i2c_device *priv = i2c_get_adapdata(adap);
	int retr;

	/* If I2C active */
	if (readb(priv->base + I2C_OFS_IICACT0) & I2C_BIT_IICE0) {
	/* Disable I2C operation */
	writeb(0, priv->base + I2C_OFS_IICACT0);

	retr = 1000;
	while (readb(priv->base + I2C_OFS_IICACT0) == 1 && retr)
	retr--;
	WARN_ON(retr == 0);
	}

	/* Transfer mode set */
	writeb(I2C_BIT_DFC0, priv->base + I2C_OFS_IICCL0);

	/* Can Issue start without detecting a stop, Reservation disabled. */
	writeb(I2C_BIT_STCEN \| I2C_BIT_IICRSV, priv->base + I2C_OFS_IICF0);

	/* I2C enable, 9 bit interrupt mode */
	writeb(I2C_BIT_WTIM0, priv->base + I2C_OFS_IICC0);

	/* Enable I2C operation */
	writeb(I2C_BIT_IICE0, priv->base + I2C_OFS_IICACT0);

	retr = 1000;
	while (readb(priv->base + I2C_OFS_IICACT0) == 0 && retr)
	retr--;
	WARN_ON(retr == 0);
	}

	static int __em_i2c_xfer(struct i2c_adapter adap, struct i2c_msg msg,
	int stop)
	{
	struct em_i2c_device *priv = i2c_get_adapdata(adap);
	int count, status, read = !!(msg->flags & I2C_M_RD);

	/* Send start condition */
	em_clear_set_bit(priv, 0, I2C_BIT_ACKE0 \| I2C_BIT_WTIM0, I2C_OFS_IICC0);
	em_clear_set_bit(priv, 0, I2C_BIT_STT0, I2C_OFS_IICC0);

	/* Send slave address and R/W type */
	writeb(i2c_8bit_addr_from_msg(msg), priv->base + I2C_OFS_IIC0);

	/* Wait for transaction */
	status = em_i2c_wait_for_event(priv);
	if (status < 0)
	goto out_reset;

	/* Received NACK (result of setting slave address and R/W) */
	if (!(status & I2C_BIT_ACKD0)) {
	em_i2c_stop(priv);
	goto out;
	}

	/* Extra setup for read transactions */
	if (read) {
	/* 8 bit interrupt mode */
	em_clear_set_bit(priv, I2C_BIT_WTIM0, I2C_BIT_ACKE0, I2C_OFS_IICC0);
	em_clear_set_bit(priv, I2C_BIT_WTIM0, I2C_BIT_WREL0, I2C_OFS_IICC0);

	/* Wait for transaction */
	status = em_i2c_wait_for_event(priv);
	if (status < 0)
	goto out_reset;
	}

	/* Send / receive data */
	for (count = 0; count < msg->len; count++) {
	if (read) { /* Read transaction */
	msg->buf[count] = readb(priv->base + I2C_OFS_IIC0);
	em_clear_set_bit(priv, 0, I2C_BIT_WREL0, I2C_OFS_IICC0);

	} else { /* Write transaction */
	/* Received NACK */
	if (!(status & I2C_BIT_ACKD0)) {
	em_i2c_stop(priv);
	goto out;
	}

	/* Write data */
	writeb(msg->buf[count], priv->base + I2C_OFS_IIC0);
	}

	/* Wait for R/W transaction */
	status = em_i2c_wait_for_event(priv);
	if (status < 0)
	goto out_reset;
	}

	if (stop)
	em_i2c_stop(priv);

	return count;

	out_reset:
	em_i2c_reset(adap);
	out:
	return status < 0 ? status : -ENXIO;
	}

	static int em_i2c_xfer(struct i2c_adapter adap, struct i2c_msg msgs,
	int num)
	{
	struct em_i2c_device *priv = i2c_get_adapdata(adap);
	int ret, i;

	if (readb(priv->base + I2C_OFS_IICF0) & I2C_BIT_IICBSY)
	return -EAGAIN;

	for (i = 0; i < num; i++) {
	ret = __em_i2c_xfer(adap, &msgs[i], (i == (num - 1)));
	if (ret < 0)
	return ret;
	}

	/* I2C transfer completed */
	return num;
	}

	static bool em_i2c_slave_irq(struct em_i2c_device *priv)
	{
	u8 status, value;
	enum i2c_slave_event event;
	int ret;

	if (!priv->slave)
	return false;

	status = readb(priv->base + I2C_OFS_IICSE0);

	/* Extension code, do not participate */
	if (status & I2C_BIT_EXC0) {
	em_clear_set_bit(priv, 0, I2C_BIT_LREL0, I2C_OFS_IICC0);
	return true;
	}

	/* Stop detected, we don't know if it's for slave or master */
	if (status & I2C_BIT_SPD0) {
	/* Notify slave device */
	i2c_slave_event(priv->slave, I2C_SLAVE_STOP, &value);
	/* Pretend we did not handle the interrupt */
	return false;
	}

	/* Only handle interrupts addressed to us */
	if (!(status & I2C_BIT_COI0))
	return false;

	/* Enable stop interrupts */
	em_clear_set_bit(priv, 0, I2C_BIT_SPIE0, I2C_OFS_IICC0);

	/* Transmission or Reception */
	if (status & I2C_BIT_TRC0) {
	if (status & I2C_BIT_ACKD0) {
	/* 9 bit interrupt mode */
	em_clear_set_bit(priv, 0, I2C_BIT_WTIM0, I2C_OFS_IICC0);

	/* Send data */
	event = status & I2C_BIT_STD0 ?
	I2C_SLAVE_READ_REQUESTED :
	I2C_SLAVE_READ_PROCESSED;
	i2c_slave_event(priv->slave, event, &value);
	writeb(value, priv->base + I2C_OFS_IIC0);
	} else {
	/* NACK, stop transmitting */
	em_clear_set_bit(priv, 0, I2C_BIT_LREL0, I2C_OFS_IICC0);
	}
	} else {
	/* 8 bit interrupt mode */
	em_clear_set_bit(priv, I2C_BIT_WTIM0, I2C_BIT_ACKE0,
	I2C_OFS_IICC0);
	em_clear_set_bit(priv, I2C_BIT_WTIM0, I2C_BIT_WREL0,
	I2C_OFS_IICC0);

	if (status & I2C_BIT_STD0) {
	i2c_slave_event(priv->slave, I2C_SLAVE_WRITE_REQUESTED,
	&value);
	} else {
	/* Recv data */
	value = readb(priv->base + I2C_OFS_IIC0);
	ret = i2c_slave_event(priv->slave,
	I2C_SLAVE_WRITE_RECEIVED, &value);
	if (ret < 0)
	em_clear_set_bit(priv, I2C_BIT_ACKE0, 0,
	I2C_OFS_IICC0);
	}
	}

	return true;
	}

	static irqreturn_t em_i2c_irq_handler(int this_irq, void *dev_id)
	{
	struct em_i2c_device *priv = dev_id;

	if (em_i2c_slave_irq(priv))
	return IRQ_HANDLED;

	complete(&priv->msg_done);

	return IRQ_HANDLED;
	}

	static u32 em_i2c_func(struct i2c_adapter *adap)
	{
	return I2C_FUNC_I2C \| I2C_FUNC_SMBUS_EMUL \| I2C_FUNC_SLAVE;
	}

	static int em_i2c_reg_slave(struct i2c_client *slave)
	{
	struct em_i2c_device *priv = i2c_get_adapdata(slave->adapter);

	if (priv->slave)
	return -EBUSY;

	if (slave->flags & I2C_CLIENT_TEN)
	return -EAFNOSUPPORT;

	priv->slave = slave;

	/* Set slave address */
	writeb(slave->addr << 1, priv->base + I2C_OFS_SVA0);

	return 0;
	}

	static int em_i2c_unreg_slave(struct i2c_client *slave)
	{
	struct em_i2c_device *priv = i2c_get_adapdata(slave->adapter);

	WARN_ON(!priv->slave);

	writeb(0, priv->base + I2C_OFS_SVA0);

	/*
	* Wait for interrupt to finish. New slave irqs cannot happen because we
	* cleared the slave address and, thus, only extension codes will be
	* detected which do not use the slave ptr.
	*/
	synchronize_irq(priv->irq);
	priv->slave = NULL;

	return 0;
	}

	static const struct i2c_algorithm em_i2c_algo = {
	.master_xfer = em_i2c_xfer,
	.functionality = em_i2c_func,
	.reg_slave = em_i2c_reg_slave,
	.unreg_slave = em_i2c_unreg_slave,
	};

	static int em_i2c_probe(struct platform_device *pdev)
	{
	struct em_i2c_device *priv;
	int ret;

	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
	if (!priv)
	return -ENOMEM;

	priv->base = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(priv->base))
	return PTR_ERR(priv->base);

	strscpy(priv->adap.name, "EMEV2 I2C", sizeof(priv->adap.name));

	priv->sclk = devm_clk_get(&pdev->dev, "sclk");
	if (IS_ERR(priv->sclk))
	return PTR_ERR(priv->sclk);

	ret = clk_prepare_enable(priv->sclk);
	if (ret)
	return ret;

	priv->adap.timeout = msecs_to_jiffies(100);
	priv->adap.retries = 5;
	priv->adap.dev.parent = &pdev->dev;
	priv->adap.algo = &em_i2c_algo;
	priv->adap.owner = THIS_MODULE;
	priv->adap.dev.of_node = pdev->dev.of_node;

	init_completion(&priv->msg_done);

	platform_set_drvdata(pdev, priv);
	i2c_set_adapdata(&priv->adap, priv);

	em_i2c_reset(&priv->adap);

	ret = platform_get_irq(pdev, 0);
	if (ret < 0)
	goto err_clk;
	priv->irq = ret;
	ret = devm_request_irq(&pdev->dev, priv->irq, em_i2c_irq_handler, 0,
	"em_i2c", priv);
	if (ret)
	goto err_clk;

	ret = i2c_add_adapter(&priv->adap);

	if (ret)
	goto err_clk;

	dev_info(&pdev->dev, "Added i2c controller %d, irq %d\n", priv->adap.nr,
	priv->irq);

	return 0;

	err_clk:
	clk_disable_unprepare(priv->sclk);
	return ret;
	}

	static void em_i2c_remove(struct platform_device *dev)
	{
	struct em_i2c_device *priv = platform_get_drvdata(dev);

	i2c_del_adapter(&priv->adap);
	clk_disable_unprepare(priv->sclk);
	}

	static const struct of_device_id em_i2c_ids[] = {
	{ .compatible = "renesas,iic-emev2", },
	{ }
	};

	static struct platform_driver em_i2c_driver = {
	.probe = em_i2c_probe,
	.remove_new = em_i2c_remove,
	.driver = {
	.name = "em-i2c",
	.of_match_table = em_i2c_ids,
	}
	};
	module_platform_driver(em_i2c_driver);

	MODULE_DESCRIPTION("EMEV2 I2C bus driver");
	MODULE_AUTHOR("Ian Molton");
	MODULE_AUTHOR("Wolfram Sang <wsa@sang-engineering.com>");
	MODULE_LICENSE("GPL v2");
	MODULE_DEVICE_TABLE(of, em_i2c_ids);