drivers/i2c/busses/i2c-mxs.c - android_kernel_htc_msm8960 - Gitiles

 /*
  * Freescale MXS I2C bus driver
  *
  * Copyright (C) 2011 Wolfram Sang, Pengutronix e.K.
  *
  * based on a (non-working) driver which was:
  *
  * Copyright (C) 2009-2010 Freescale Semiconductor, Inc. All Rights Reserved.
  *
  * TODO: add dma-support if platform-support for it is available
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.
  *
  */

 #include <linux/slab.h>
 #include <linux/device.h>
 #include <linux/module.h>
 #include <linux/i2c.h>
 #include <linux/err.h>
 #include <linux/interrupt.h>
 #include <linux/completion.h>
 #include <linux/platform_device.h>
 #include <linux/jiffies.h>
 #include <linux/io.h>

 #include <mach/common.h>

 #define DRIVER_NAME "mxs-i2c"

 #define MXS_I2C_CTRL0		(0x00)
 #define MXS_I2C_CTRL0_SET	(0x04)

 #define MXS_I2C_CTRL0_SFTRST			0x80000000
 #define MXS_I2C_CTRL0_SEND_NAK_ON_LAST		0x02000000
 #define MXS_I2C_CTRL0_RETAIN_CLOCK		0x00200000
 #define MXS_I2C_CTRL0_POST_SEND_STOP		0x00100000
 #define MXS_I2C_CTRL0_PRE_SEND_START		0x00080000
 #define MXS_I2C_CTRL0_MASTER_MODE		0x00020000
 #define MXS_I2C_CTRL0_DIRECTION			0x00010000
 #define MXS_I2C_CTRL0_XFER_COUNT(v)		((v) & 0x0000FFFF)

 #define MXS_I2C_CTRL1		(0x40)
 #define MXS_I2C_CTRL1_SET	(0x44)
 #define MXS_I2C_CTRL1_CLR	(0x48)

 #define MXS_I2C_CTRL1_BUS_FREE_IRQ		0x80
 #define MXS_I2C_CTRL1_DATA_ENGINE_CMPLT_IRQ	0x40
 #define MXS_I2C_CTRL1_NO_SLAVE_ACK_IRQ		0x20
 #define MXS_I2C_CTRL1_OVERSIZE_XFER_TERM_IRQ	0x10
 #define MXS_I2C_CTRL1_EARLY_TERM_IRQ		0x08
 #define MXS_I2C_CTRL1_MASTER_LOSS_IRQ		0x04
 #define MXS_I2C_CTRL1_SLAVE_STOP_IRQ		0x02
 #define MXS_I2C_CTRL1_SLAVE_IRQ			0x01

 #define MXS_I2C_IRQ_MASK	(MXS_I2C_CTRL1_DATA_ENGINE_CMPLT_IRQ | \
 				 MXS_I2C_CTRL1_NO_SLAVE_ACK_IRQ | \
 				 MXS_I2C_CTRL1_EARLY_TERM_IRQ | \
 				 MXS_I2C_CTRL1_MASTER_LOSS_IRQ | \
 				 MXS_I2C_CTRL1_SLAVE_STOP_IRQ | \
 				 MXS_I2C_CTRL1_SLAVE_IRQ)

 #define MXS_I2C_QUEUECTRL	(0x60)
 #define MXS_I2C_QUEUECTRL_SET	(0x64)
 #define MXS_I2C_QUEUECTRL_CLR	(0x68)

 #define MXS_I2C_QUEUECTRL_QUEUE_RUN		0x20
 #define MXS_I2C_QUEUECTRL_PIO_QUEUE_MODE	0x04

 #define MXS_I2C_QUEUESTAT	(0x70)
 #define MXS_I2C_QUEUESTAT_RD_QUEUE_EMPTY        0x00002000

 #define MXS_I2C_QUEUECMD	(0x80)

 #define MXS_I2C_QUEUEDATA	(0x90)

 #define MXS_I2C_DATA		(0xa0)


 #define MXS_CMD_I2C_SELECT	(MXS_I2C_CTRL0_RETAIN_CLOCK |	\
 				 MXS_I2C_CTRL0_PRE_SEND_START |	\
 				 MXS_I2C_CTRL0_MASTER_MODE |	\
 				 MXS_I2C_CTRL0_DIRECTION |	\
 				 MXS_I2C_CTRL0_XFER_COUNT(1))

 #define MXS_CMD_I2C_WRITE	(MXS_I2C_CTRL0_PRE_SEND_START |	\
 				 MXS_I2C_CTRL0_MASTER_MODE |	\
 				 MXS_I2C_CTRL0_DIRECTION)

 #define MXS_CMD_I2C_READ	(MXS_I2C_CTRL0_SEND_NAK_ON_LAST | \
 				 MXS_I2C_CTRL0_MASTER_MODE)

 /**
  * struct mxs_i2c_dev - per device, private MXS-I2C data
  *
  * @dev: driver model device node
  * @regs: IO registers pointer
  * @cmd_complete: completion object for transaction wait
  * @cmd_err: error code for last transaction
  * @adapter: i2c subsystem adapter node
  */
 struct mxs_i2c_dev {
 	struct device *dev;
 	void __iomem *regs;
 	struct completion cmd_complete;
 	u32 cmd_err;
 	struct i2c_adapter adapter;
 };

 /*
  * TODO: check if calls to here are really needed. If not, we could get rid of
  * mxs_reset_block and the mach-dependency. Needs an I2C analyzer, probably.
  */
 static void mxs_i2c_reset(struct mxs_i2c_dev *i2c)
 {
 	mxs_reset_block(i2c->regs);
 	writel(MXS_I2C_IRQ_MASK << 8, i2c->regs + MXS_I2C_CTRL1_SET);
 	writel(MXS_I2C_QUEUECTRL_PIO_QUEUE_MODE,
 			i2c->regs + MXS_I2C_QUEUECTRL_SET);
 }

 static void mxs_i2c_pioq_setup_read(struct mxs_i2c_dev *i2c, u8 addr, int len,
 					int flags)
 {
 	u32 data;

 	writel(MXS_CMD_I2C_SELECT, i2c->regs + MXS_I2C_QUEUECMD);

 	data = (addr << 1) | I2C_SMBUS_READ;
 	writel(data, i2c->regs + MXS_I2C_DATA);

 	data = MXS_CMD_I2C_READ | MXS_I2C_CTRL0_XFER_COUNT(len) | flags;
 	writel(data, i2c->regs + MXS_I2C_QUEUECMD);
 }

 static void mxs_i2c_pioq_setup_write(struct mxs_i2c_dev *i2c,
 				    u8 addr, u8 *buf, int len, int flags)
 {
 	u32 data;
 	int i, shifts_left;

 	data = MXS_CMD_I2C_WRITE | MXS_I2C_CTRL0_XFER_COUNT(len + 1) | flags;
 	writel(data, i2c->regs + MXS_I2C_QUEUECMD);

 	/*
 	 * We have to copy the slave address (u8) and buffer (arbitrary number
 	 * of u8) into the data register (u32). To achieve that, the u8 are put
 	 * into the MSBs of 'data' which is then shifted for the next u8. When
 	 * appropriate, 'data' is written to MXS_I2C_DATA. So, the first u32
 	 * looks like this:
 	 *
 	 *  3          2          1          0
 	 * 10987654|32109876|54321098|76543210
 	 * --------+--------+--------+--------
 	 * buffer+2|buffer+1|buffer+0|slave_addr
 	 */

 	data = ((addr << 1) | I2C_SMBUS_WRITE) << 24;

 	for (i = 0; i < len; i++) {
 		data >>= 8;
 		data |= buf[i] << 24;
 		if ((i & 3) == 2)
 			writel(data, i2c->regs + MXS_I2C_DATA);
 	}

 	/* Write out the remaining bytes if any */
 	shifts_left = 24 - (i & 3) * 8;
 	if (shifts_left)
 		writel(data >> shifts_left, i2c->regs + MXS_I2C_DATA);
 }

 /*
  * TODO: should be replaceable with a waitqueue and RD_QUEUE_IRQ (setting the
  * rd_threshold to 1). Couldn't get this to work, though.
  */
 static int mxs_i2c_wait_for_data(struct mxs_i2c_dev *i2c)
 {
 	unsigned long timeout = jiffies + msecs_to_jiffies(1000);

 	while (readl(i2c->regs + MXS_I2C_QUEUESTAT)
 			& MXS_I2C_QUEUESTAT_RD_QUEUE_EMPTY) {
 			if (time_after(jiffies, timeout))
 				return -ETIMEDOUT;
 			cond_resched();
 	}

 	return 0;
 }

 static int mxs_i2c_finish_read(struct mxs_i2c_dev *i2c, u8 *buf, int len)
 {
 	u32 data;
 	int i;

 	for (i = 0; i < len; i++) {
 		if ((i & 3) == 0) {
 			if (mxs_i2c_wait_for_data(i2c))
 				return -ETIMEDOUT;
 			data = readl(i2c->regs + MXS_I2C_QUEUEDATA);
 		}
 		buf[i] = data & 0xff;
 		data >>= 8;
 	}

 	return 0;
 }

 /*
  * Low level master read/write transaction.
  */
 static int mxs_i2c_xfer_msg(struct i2c_adapter *adap, struct i2c_msg *msg,
 				int stop)
 {
 	struct mxs_i2c_dev *i2c = i2c_get_adapdata(adap);
 	int ret;
 	int flags;

 	init_completion(&i2c->cmd_complete);

 	dev_dbg(i2c->dev, "addr: 0x%04x, len: %d, flags: 0x%x, stop: %d\n",
 		msg->addr, msg->len, msg->flags, stop);

 	if (msg->len == 0)
 		return -EINVAL;

 	flags = stop ? MXS_I2C_CTRL0_POST_SEND_STOP : 0;

 	if (msg->flags & I2C_M_RD)
 		mxs_i2c_pioq_setup_read(i2c, msg->addr, msg->len, flags);
 	else
 		mxs_i2c_pioq_setup_write(i2c, msg->addr, msg->buf, msg->len,
 					flags);

 	writel(MXS_I2C_QUEUECTRL_QUEUE_RUN,
 			i2c->regs + MXS_I2C_QUEUECTRL_SET);

 	ret = wait_for_completion_timeout(&i2c->cmd_complete,
 						msecs_to_jiffies(1000));
 	if (ret == 0)
 		goto timeout;

 	if ((!i2c->cmd_err) && (msg->flags & I2C_M_RD)) {
 		ret = mxs_i2c_finish_read(i2c, msg->buf, msg->len);
 		if (ret)
 			goto timeout;
 	}

 	if (i2c->cmd_err == -ENXIO)
 		mxs_i2c_reset(i2c);

 	dev_dbg(i2c->dev, "Done with err=%d\n", i2c->cmd_err);

 	return i2c->cmd_err;

 timeout:
 	dev_dbg(i2c->dev, "Timeout!\n");
 	mxs_i2c_reset(i2c);
 	return -ETIMEDOUT;
 }

 static int mxs_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
 			int num)
 {
 	int i;
 	int err;

 	for (i = 0; i < num; i++) {
 		err = mxs_i2c_xfer_msg(adap, &msgs[i], i == (num - 1));
 		if (err)
 			return err;
 	}

 	return num;
 }

 static u32 mxs_i2c_func(struct i2c_adapter *adap)
 {
 	return I2C_FUNC_I2C | (I2C_FUNC_SMBUS_EMUL & ~I2C_FUNC_SMBUS_QUICK);
 }

 static irqreturn_t mxs_i2c_isr(int this_irq, void *dev_id)
 {
 	struct mxs_i2c_dev *i2c = dev_id;
 	u32 stat = readl(i2c->regs + MXS_I2C_CTRL1) & MXS_I2C_IRQ_MASK;

 	if (!stat)
 		return IRQ_NONE;

 	if (stat & MXS_I2C_CTRL1_NO_SLAVE_ACK_IRQ)
 		i2c->cmd_err = -ENXIO;
 	else if (stat & (MXS_I2C_CTRL1_EARLY_TERM_IRQ |
 		    MXS_I2C_CTRL1_MASTER_LOSS_IRQ |
 		    MXS_I2C_CTRL1_SLAVE_STOP_IRQ | MXS_I2C_CTRL1_SLAVE_IRQ))
 		/* MXS_I2C_CTRL1_OVERSIZE_XFER_TERM_IRQ is only for slaves */
 		i2c->cmd_err = -EIO;
 	else
 		i2c->cmd_err = 0;

 	complete(&i2c->cmd_complete);

 	writel(stat, i2c->regs + MXS_I2C_CTRL1_CLR);
 	return IRQ_HANDLED;
 }

 static const struct i2c_algorithm mxs_i2c_algo = {
 	.master_xfer = mxs_i2c_xfer,
 	.functionality = mxs_i2c_func,
 };

 static int __devinit mxs_i2c_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
 	struct mxs_i2c_dev *i2c;
 	struct i2c_adapter *adap;
 	struct resource *res;
 	resource_size_t res_size;
 	int err, irq;

 	i2c = devm_kzalloc(dev, sizeof(struct mxs_i2c_dev), GFP_KERNEL);
 	if (!i2c)
 		return -ENOMEM;

 	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	if (!res)
 		return -ENOENT;

 	res_size = resource_size(res);
 	if (!devm_request_mem_region(dev, res->start, res_size, res->name))
 		return -EBUSY;

 	i2c->regs = devm_ioremap_nocache(dev, res->start, res_size);
 	if (!i2c->regs)
 		return -EBUSY;

 	irq = platform_get_irq(pdev, 0);
 	if (irq < 0)
 		return irq;

 	err = devm_request_irq(dev, irq, mxs_i2c_isr, 0, dev_name(dev), i2c);
 	if (err)
 		return err;

 	i2c->dev = dev;
 	platform_set_drvdata(pdev, i2c);

 	/* Do reset to enforce correct startup after pinmuxing */
 	mxs_i2c_reset(i2c);

 	adap = &i2c->adapter;
 	strlcpy(adap->name, "MXS I2C adapter", sizeof(adap->name));
 	adap->owner = THIS_MODULE;
 	adap->algo = &mxs_i2c_algo;
 	adap->dev.parent = dev;
 	adap->nr = pdev->id;
 	i2c_set_adapdata(adap, i2c);
 	err = i2c_add_numbered_adapter(adap);
 	if (err) {
 		dev_err(dev, "Failed to add adapter (%d)\n", err);
 		writel(MXS_I2C_CTRL0_SFTRST,
 				i2c->regs + MXS_I2C_CTRL0_SET);
 		return err;
 	}

 	return 0;
 }

 static int __devexit mxs_i2c_remove(struct platform_device *pdev)
 {
 	struct mxs_i2c_dev *i2c = platform_get_drvdata(pdev);
 	int ret;

 	ret = i2c_del_adapter(&i2c->adapter);
 	if (ret)
 		return -EBUSY;

 	writel(MXS_I2C_QUEUECTRL_QUEUE_RUN,
 			i2c->regs + MXS_I2C_QUEUECTRL_CLR);
 	writel(MXS_I2C_CTRL0_SFTRST, i2c->regs + MXS_I2C_CTRL0_SET);

 	platform_set_drvdata(pdev, NULL);

 	return 0;
 }

 static struct platform_driver mxs_i2c_driver = {
 	.driver = {
 		   .name = DRIVER_NAME,
 		   .owner = THIS_MODULE,
 		   },
 	.remove = __devexit_p(mxs_i2c_remove),
 };

 static int __init mxs_i2c_init(void)
 {
 	return platform_driver_probe(&mxs_i2c_driver, mxs_i2c_probe);
 }
 subsys_initcall(mxs_i2c_init);

 static void __exit mxs_i2c_exit(void)
 {
 	platform_driver_unregister(&mxs_i2c_driver);
 }
 module_exit(mxs_i2c_exit);

 MODULE_AUTHOR("Wolfram Sang <w.sang@pengutronix.de>");
 MODULE_DESCRIPTION("MXS I2C Bus Driver");
 MODULE_LICENSE("GPL");
 MODULE_ALIAS("platform:" DRIVER_NAME);
	/*
	* Freescale MXS I2C bus driver
	*
	* Copyright (C) 2011 Wolfram Sang, Pengutronix e.K.
	*
	* based on a (non-working) driver which was:
	*
	* Copyright (C) 2009-2010 Freescale Semiconductor, Inc. All Rights Reserved.
	*
	* TODO: add dma-support if platform-support for it is available
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	*/

	#include <linux/slab.h>
	#include <linux/device.h>
	#include <linux/module.h>
	#include <linux/i2c.h>
	#include <linux/err.h>
	#include <linux/interrupt.h>
	#include <linux/completion.h>
	#include <linux/platform_device.h>
	#include <linux/jiffies.h>
	#include <linux/io.h>

	#include <mach/common.h>

	#define DRIVER_NAME "mxs-i2c"

	#define MXS_I2C_CTRL0 (0x00)
	#define MXS_I2C_CTRL0_SET (0x04)

	#define MXS_I2C_CTRL0_SFTRST 0x80000000
	#define MXS_I2C_CTRL0_SEND_NAK_ON_LAST 0x02000000
	#define MXS_I2C_CTRL0_RETAIN_CLOCK 0x00200000
	#define MXS_I2C_CTRL0_POST_SEND_STOP 0x00100000
	#define MXS_I2C_CTRL0_PRE_SEND_START 0x00080000
	#define MXS_I2C_CTRL0_MASTER_MODE 0x00020000
	#define MXS_I2C_CTRL0_DIRECTION 0x00010000
	#define MXS_I2C_CTRL0_XFER_COUNT(v) ((v) & 0x0000FFFF)

	#define MXS_I2C_CTRL1 (0x40)
	#define MXS_I2C_CTRL1_SET (0x44)
	#define MXS_I2C_CTRL1_CLR (0x48)

	#define MXS_I2C_CTRL1_BUS_FREE_IRQ 0x80
	#define MXS_I2C_CTRL1_DATA_ENGINE_CMPLT_IRQ 0x40
	#define MXS_I2C_CTRL1_NO_SLAVE_ACK_IRQ 0x20
	#define MXS_I2C_CTRL1_OVERSIZE_XFER_TERM_IRQ 0x10
	#define MXS_I2C_CTRL1_EARLY_TERM_IRQ 0x08
	#define MXS_I2C_CTRL1_MASTER_LOSS_IRQ 0x04
	#define MXS_I2C_CTRL1_SLAVE_STOP_IRQ 0x02
	#define MXS_I2C_CTRL1_SLAVE_IRQ 0x01

	#define MXS_I2C_IRQ_MASK (MXS_I2C_CTRL1_DATA_ENGINE_CMPLT_IRQ \| \
	MXS_I2C_CTRL1_NO_SLAVE_ACK_IRQ \| \
	MXS_I2C_CTRL1_EARLY_TERM_IRQ \| \
	MXS_I2C_CTRL1_MASTER_LOSS_IRQ \| \
	MXS_I2C_CTRL1_SLAVE_STOP_IRQ \| \
	MXS_I2C_CTRL1_SLAVE_IRQ)

	#define MXS_I2C_QUEUECTRL (0x60)
	#define MXS_I2C_QUEUECTRL_SET (0x64)
	#define MXS_I2C_QUEUECTRL_CLR (0x68)

	#define MXS_I2C_QUEUECTRL_QUEUE_RUN 0x20
	#define MXS_I2C_QUEUECTRL_PIO_QUEUE_MODE 0x04

	#define MXS_I2C_QUEUESTAT (0x70)
	#define MXS_I2C_QUEUESTAT_RD_QUEUE_EMPTY 0x00002000

	#define MXS_I2C_QUEUECMD (0x80)

	#define MXS_I2C_QUEUEDATA (0x90)

	#define MXS_I2C_DATA (0xa0)


	#define MXS_CMD_I2C_SELECT (MXS_I2C_CTRL0_RETAIN_CLOCK \| \
	MXS_I2C_CTRL0_PRE_SEND_START \| \
	MXS_I2C_CTRL0_MASTER_MODE \| \
	MXS_I2C_CTRL0_DIRECTION \| \
	MXS_I2C_CTRL0_XFER_COUNT(1))

	#define MXS_CMD_I2C_WRITE (MXS_I2C_CTRL0_PRE_SEND_START \| \
	MXS_I2C_CTRL0_MASTER_MODE \| \
	MXS_I2C_CTRL0_DIRECTION)

	#define MXS_CMD_I2C_READ (MXS_I2C_CTRL0_SEND_NAK_ON_LAST \| \
	MXS_I2C_CTRL0_MASTER_MODE)

	/**
	* struct mxs_i2c_dev - per device, private MXS-I2C data
	*
	* @dev: driver model device node
	* @regs: IO registers pointer
	* @cmd_complete: completion object for transaction wait
	* @cmd_err: error code for last transaction
	* @adapter: i2c subsystem adapter node
	*/
	struct mxs_i2c_dev {
	struct device *dev;
	void __iomem *regs;
	struct completion cmd_complete;
	u32 cmd_err;
	struct i2c_adapter adapter;
	};

	/*
	* TODO: check if calls to here are really needed. If not, we could get rid of
	* mxs_reset_block and the mach-dependency. Needs an I2C analyzer, probably.
	*/
	static void mxs_i2c_reset(struct mxs_i2c_dev *i2c)
	{
	mxs_reset_block(i2c->regs);
	writel(MXS_I2C_IRQ_MASK << 8, i2c->regs + MXS_I2C_CTRL1_SET);
	writel(MXS_I2C_QUEUECTRL_PIO_QUEUE_MODE,
	i2c->regs + MXS_I2C_QUEUECTRL_SET);
	}

	static void mxs_i2c_pioq_setup_read(struct mxs_i2c_dev *i2c, u8 addr, int len,
	int flags)
	{
	u32 data;

	writel(MXS_CMD_I2C_SELECT, i2c->regs + MXS_I2C_QUEUECMD);

	data = (addr << 1) \| I2C_SMBUS_READ;
	writel(data, i2c->regs + MXS_I2C_DATA);

	data = MXS_CMD_I2C_READ \| MXS_I2C_CTRL0_XFER_COUNT(len) \| flags;
	writel(data, i2c->regs + MXS_I2C_QUEUECMD);
	}

	static void mxs_i2c_pioq_setup_write(struct mxs_i2c_dev *i2c,
	u8 addr, u8 *buf, int len, int flags)
	{
	u32 data;
	int i, shifts_left;

	data = MXS_CMD_I2C_WRITE \| MXS_I2C_CTRL0_XFER_COUNT(len + 1) \| flags;
	writel(data, i2c->regs + MXS_I2C_QUEUECMD);

	/*
	* We have to copy the slave address (u8) and buffer (arbitrary number
	* of u8) into the data register (u32). To achieve that, the u8 are put
	* into the MSBs of 'data' which is then shifted for the next u8. When
	* appropriate, 'data' is written to MXS_I2C_DATA. So, the first u32
	* looks like this:
	*
	* 3 2 1 0
	* 10987654\|32109876\|54321098\|76543210
	* --------+--------+--------+--------
	* buffer+2\|buffer+1\|buffer+0\|slave_addr
	*/

	data = ((addr << 1) \| I2C_SMBUS_WRITE) << 24;

	for (i = 0; i < len; i++) {
	data >>= 8;
	data \|= buf[i] << 24;
	if ((i & 3) == 2)
	writel(data, i2c->regs + MXS_I2C_DATA);
	}

	/* Write out the remaining bytes if any */
	shifts_left = 24 - (i & 3) * 8;
	if (shifts_left)
	writel(data >> shifts_left, i2c->regs + MXS_I2C_DATA);
	}

	/*
	* TODO: should be replaceable with a waitqueue and RD_QUEUE_IRQ (setting the
	* rd_threshold to 1). Couldn't get this to work, though.
	*/
	static int mxs_i2c_wait_for_data(struct mxs_i2c_dev *i2c)
	{
	unsigned long timeout = jiffies + msecs_to_jiffies(1000);

	while (readl(i2c->regs + MXS_I2C_QUEUESTAT)
	& MXS_I2C_QUEUESTAT_RD_QUEUE_EMPTY) {
	if (time_after(jiffies, timeout))
	return -ETIMEDOUT;
	cond_resched();
	}

	return 0;
	}

	static int mxs_i2c_finish_read(struct mxs_i2c_dev i2c, u8 buf, int len)
	{
	u32 data;
	int i;

	for (i = 0; i < len; i++) {
	if ((i & 3) == 0) {
	if (mxs_i2c_wait_for_data(i2c))
	return -ETIMEDOUT;
	data = readl(i2c->regs + MXS_I2C_QUEUEDATA);
	}
	buf[i] = data & 0xff;
	data >>= 8;
	}

	return 0;
	}

	/*
	* Low level master read/write transaction.
	*/
	static int mxs_i2c_xfer_msg(struct i2c_adapter adap, struct i2c_msg msg,
	int stop)
	{
	struct mxs_i2c_dev *i2c = i2c_get_adapdata(adap);
	int ret;
	int flags;

	init_completion(&i2c->cmd_complete);

	dev_dbg(i2c->dev, "addr: 0x%04x, len: %d, flags: 0x%x, stop: %d\n",
	msg->addr, msg->len, msg->flags, stop);

	if (msg->len == 0)
	return -EINVAL;

	flags = stop ? MXS_I2C_CTRL0_POST_SEND_STOP : 0;

	if (msg->flags & I2C_M_RD)
	mxs_i2c_pioq_setup_read(i2c, msg->addr, msg->len, flags);
	else
	mxs_i2c_pioq_setup_write(i2c, msg->addr, msg->buf, msg->len,
	flags);

	writel(MXS_I2C_QUEUECTRL_QUEUE_RUN,
	i2c->regs + MXS_I2C_QUEUECTRL_SET);

	ret = wait_for_completion_timeout(&i2c->cmd_complete,
	msecs_to_jiffies(1000));
	if (ret == 0)
	goto timeout;

	if ((!i2c->cmd_err) && (msg->flags & I2C_M_RD)) {
	ret = mxs_i2c_finish_read(i2c, msg->buf, msg->len);
	if (ret)
	goto timeout;
	}

	if (i2c->cmd_err == -ENXIO)
	mxs_i2c_reset(i2c);

	dev_dbg(i2c->dev, "Done with err=%d\n", i2c->cmd_err);

	return i2c->cmd_err;

	timeout:
	dev_dbg(i2c->dev, "Timeout!\n");
	mxs_i2c_reset(i2c);
	return -ETIMEDOUT;
	}

	static int mxs_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[],
	int num)
	{
	int i;
	int err;

	for (i = 0; i < num; i++) {
	err = mxs_i2c_xfer_msg(adap, &msgs[i], i == (num - 1));
	if (err)
	return err;
	}

	return num;
	}

	static u32 mxs_i2c_func(struct i2c_adapter *adap)
	{
	return I2C_FUNC_I2C \| (I2C_FUNC_SMBUS_EMUL & ~I2C_FUNC_SMBUS_QUICK);
	}

	static irqreturn_t mxs_i2c_isr(int this_irq, void *dev_id)
	{
	struct mxs_i2c_dev *i2c = dev_id;
	u32 stat = readl(i2c->regs + MXS_I2C_CTRL1) & MXS_I2C_IRQ_MASK;

	if (!stat)
	return IRQ_NONE;

	if (stat & MXS_I2C_CTRL1_NO_SLAVE_ACK_IRQ)
	i2c->cmd_err = -ENXIO;
	else if (stat & (MXS_I2C_CTRL1_EARLY_TERM_IRQ \|
	MXS_I2C_CTRL1_MASTER_LOSS_IRQ \|
	MXS_I2C_CTRL1_SLAVE_STOP_IRQ \| MXS_I2C_CTRL1_SLAVE_IRQ))
	/* MXS_I2C_CTRL1_OVERSIZE_XFER_TERM_IRQ is only for slaves */
	i2c->cmd_err = -EIO;
	else
	i2c->cmd_err = 0;

	complete(&i2c->cmd_complete);

	writel(stat, i2c->regs + MXS_I2C_CTRL1_CLR);
	return IRQ_HANDLED;
	}

	static const struct i2c_algorithm mxs_i2c_algo = {
	.master_xfer = mxs_i2c_xfer,
	.functionality = mxs_i2c_func,
	};

	static int __devinit mxs_i2c_probe(struct platform_device *pdev)
	{
	struct device *dev = &pdev->dev;
	struct mxs_i2c_dev *i2c;
	struct i2c_adapter *adap;
	struct resource *res;
	resource_size_t res_size;
	int err, irq;

	i2c = devm_kzalloc(dev, sizeof(struct mxs_i2c_dev), GFP_KERNEL);
	if (!i2c)
	return -ENOMEM;

	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
	if (!res)
	return -ENOENT;

	res_size = resource_size(res);
	if (!devm_request_mem_region(dev, res->start, res_size, res->name))
	return -EBUSY;

	i2c->regs = devm_ioremap_nocache(dev, res->start, res_size);
	if (!i2c->regs)
	return -EBUSY;

	irq = platform_get_irq(pdev, 0);
	if (irq < 0)
	return irq;

	err = devm_request_irq(dev, irq, mxs_i2c_isr, 0, dev_name(dev), i2c);
	if (err)
	return err;

	i2c->dev = dev;
	platform_set_drvdata(pdev, i2c);

	/* Do reset to enforce correct startup after pinmuxing */
	mxs_i2c_reset(i2c);

	adap = &i2c->adapter;
	strlcpy(adap->name, "MXS I2C adapter", sizeof(adap->name));
	adap->owner = THIS_MODULE;
	adap->algo = &mxs_i2c_algo;
	adap->dev.parent = dev;
	adap->nr = pdev->id;
	i2c_set_adapdata(adap, i2c);
	err = i2c_add_numbered_adapter(adap);
	if (err) {
	dev_err(dev, "Failed to add adapter (%d)\n", err);
	writel(MXS_I2C_CTRL0_SFTRST,
	i2c->regs + MXS_I2C_CTRL0_SET);
	return err;
	}

	return 0;
	}

	static int __devexit mxs_i2c_remove(struct platform_device *pdev)
	{
	struct mxs_i2c_dev *i2c = platform_get_drvdata(pdev);
	int ret;

	ret = i2c_del_adapter(&i2c->adapter);
	if (ret)
	return -EBUSY;

	writel(MXS_I2C_QUEUECTRL_QUEUE_RUN,
	i2c->regs + MXS_I2C_QUEUECTRL_CLR);
	writel(MXS_I2C_CTRL0_SFTRST, i2c->regs + MXS_I2C_CTRL0_SET);

	platform_set_drvdata(pdev, NULL);

	return 0;
	}

	static struct platform_driver mxs_i2c_driver = {
	.driver = {
	.name = DRIVER_NAME,
	.owner = THIS_MODULE,
	},
	.remove = __devexit_p(mxs_i2c_remove),
	};

	static int __init mxs_i2c_init(void)
	{
	return platform_driver_probe(&mxs_i2c_driver, mxs_i2c_probe);
	}
	subsys_initcall(mxs_i2c_init);

	static void __exit mxs_i2c_exit(void)
	{
	platform_driver_unregister(&mxs_i2c_driver);
	}
	module_exit(mxs_i2c_exit);

	MODULE_AUTHOR("Wolfram Sang <w.sang@pengutronix.de>");
	MODULE_DESCRIPTION("MXS I2C Bus Driver");
	MODULE_LICENSE("GPL");
	MODULE_ALIAS("platform:" DRIVER_NAME);