I2C驱动分析

#include
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/** Defines ********************************************************************
*******************************************************************************/

/* This will be the driver name the kernel reports */
#define DRIVER_NAME "imx-i2c"

/* Default value */
#define IMX_I2C_BIT_RATE 100000 /* 100kHz */

/* IMX I2C registers */
#define IMX_I2C_IADR 0x00 /* i2c slave address */
#define IMX_I2C_IFDR 0x04 /* i2c frequency divider */
#define IMX_I2C_I2CR 0x08 /* i2c control */
#define IMX_I2C_I2SR 0x0C /* i2c status */
#define IMX_I2C_I2DR 0x10 /* i2c transfer data */

/* Bits of IMX I2C registers */
#define I2SR_RXAK 0x01
#define I2SR_IIF 0x02
#define I2SR_SRW 0x04
#define I2SR_IAL 0x10
#define I2SR_IBB 0x20
#define I2SR_IAAS 0x40
#define I2SR_ICF 0x80
#define I2CR_RSTA 0x04
#define I2CR_TXAK 0x08
#define I2CR_MTX 0x10
#define I2CR_MSTA 0x20
#define I2CR_IIEN 0x40
#define I2CR_IEN 0x80

/** Variables ******************************************************************
*******************************************************************************/

/*
 * sorted list of clock divider, register value pairs
 * taken from table 26-5, p.26-9, Freescale i.MX
 * Integrated Portable System Processor Reference Manual
 * Document Number: MC9328MXLRM, Rev. 5.1, 06/2007
 *
 * Duplicated divider values removed from list
 */

static u16 __initdata i2c_clk_div[50][2] = {
 { 22, 0x20 }, { 24, 0x21 }, { 26, 0x22 }, { 28, 0x23 },
 { 30, 0x00 }, { 32, 0x24 }, { 36, 0x25 }, { 40, 0x26 },
 { 42, 0x03 }, { 44, 0x27 }, { 48, 0x28 }, { 52, 0x05 },
 { 56, 0x29 }, { 60, 0x06 }, { 64, 0x2A }, { 72, 0x2B },
 { 80, 0x2C }, { 88, 0x09 }, { 96, 0x2D }, { 104, 0x0A },
 { 112, 0x2E }, { 128, 0x2F }, { 144, 0x0C }, { 160, 0x30 },
 { 192, 0x31 }, { 224, 0x32 }, { 240, 0x0F }, { 256, 0x33 },
 { 288, 0x10 }, { 320, 0x34 }, { 384, 0x35 }, { 448, 0x36 },
 { 480, 0x13 }, { 512, 0x37 }, { 576, 0x14 }, { 640, 0x38 },
 { 768, 0x39 }, { 896, 0x3A }, { 960, 0x17 }, { 1024, 0x3B },
 { 1152, 0x18 }, { 1280, 0x3C }, { 1536, 0x3D }, { 1792, 0x3E },
 { 1920, 0x1B }, { 2048, 0x3F }, { 2304, 0x1C }, { 2560, 0x1D },
 { 3072, 0x1E }, { 3840, 0x1F }
};

struct imx_i2c_struct {
 struct i2c_adapter adapter;                 //记录当前适配器
 struct resource  *res;    //i2c控制器资源
 struct clk  *clk;    //当前时钟
 void __iomem  *base;        //用于记录当前控制器的寄存器虚拟地址
 int   irq;   //当前控制器中断
 wait_queue_head_t queue;    //等待队列
 unsigned long  i2csr;
 unsigned int   disable_delay;
 int   stopped;
 unsigned int  ifdr; /* IMX_I2C_IFDR */
};

/** Functions for IMX I2C adapter driver ***************************************
*******************************************************************************/

//判断IIC总线是不是处于忙状态
static int i2c_imx_bus_busy(struct imx_i2c_struct *i2c_imx, int for_busy)
{
 unsigned long orig_jiffies = jiffies;
 unsigned int temp;

 dev_dbg(&i2c_imx->adapter.dev, "<%s>\n", __func__);

 while (1) {
  temp = readb(i2c_imx->base + IMX_I2C_I2SR);
  if (for_busy && (temp & I2SR_IBB))  //为空闲状态则跳出循环否则继续等待(IBB位的状态反映出当前总线的状态)
   break;
  if (!for_busy && !(temp & I2SR_IBB))
   break;
  if (signal_pending(current)) {
   dev_dbg(&i2c_imx->adapter.dev,
    "<%s> I2C Interrupted\n", __func__);
   return -EINTR;
  }
  if (time_after(jiffies, orig_jiffies + msecs_to_jiffies(500))) {     // 超出500ms就认为是超时发生
   dev_dbg(&i2c_imx->adapter.dev,
    "<%s> I2C bus is busy\n", __func__);
   return -ETIMEDOUT;
  }
  schedule();                       //没有超时则继续等待此处是让出CPU，来执行其它的进程并等待下次该进程被调度后来重新判断
 }

 return 0;
}

static int i2c_imx_trx_complete(struct imx_i2c_struct *i2c_imx)
{
 wait_event_timeout(i2c_imx->queue, i2c_imx->i2csr & I2SR_IIF, HZ / 10); //查看数据是否发送完毕(即IIF位是否被置位)如果没有被置位且没有超时则在等待队列上睡眠来继续等待.

 if (unlikely(!(i2c_imx->i2csr & I2SR_IIF))) {               //查看是否起时，是则返回超时错误，否则发送成功
  dev_dbg(&i2c_imx->adapter.dev, "<%s> Timeout\n", __func__);
  return -ETIMEDOUT;
 }
 dev_dbg(&i2c_imx->adapter.dev, "<%s> TRX complete\n", __func__);
 i2c_imx->i2csr = 0;
 return 0;
}

static int i2c_imx_acked(struct imx_i2c_struct *i2c_imx)
{
 if (readb(i2c_imx->base + IMX_I2C_I2SR) & I2SR_RXAK) {                  //判断ACK信号是否到达
  dev_dbg(&i2c_imx->adapter.dev, "<%s> No ACK\n", __func__);
  return -EIO;  /* No ACK */
 }

 dev_dbg(&i2c_imx->adapter.dev, "<%s> ACK received\n", __func__);
 return 0;
}

//发送START信号
static int i2c_imx_start(struct imx_i2c_struct *i2c_imx)
{
 unsigned int temp = 0;
 int result;

 dev_dbg(&i2c_imx->adapter.dev, "<%s>\n", __func__);

 clk_enable(i2c_imx->clk);
 writeb(i2c_imx->ifdr, i2c_imx->base + IMX_I2C_IFDR); //设置IIC的工作频率
 /* Enable I2C controller */
 writeb(0, i2c_imx->base + IMX_I2C_I2SR);            //清除状态位
 writeb(I2CR_IEN, i2c_imx->base + IMX_I2C_I2CR);      //使能IIC控制器

 /* Wait controller to be stable */
 udelay(50);

 /* Start I2C transaction */
 temp = readb(i2c_imx->base + IMX_I2C_I2CR);
 temp |= I2CR_MSTA;    //I2CR中的MSTA位的默认值为0，而在此时若将其置位即有一个0到1的过程则控制器会到IIC总线上产生一个开始信号并将控制器设置成主模式
 writeb(temp, i2c_imx->base + IMX_I2C_I2CR);
 result = i2c_imx_bus_busy(i2c_imx, 1);
 if (result)
  return result;
 i2c_imx->stopped = 0;

 temp |= I2CR_IIEN | I2CR_MTX | I2CR_TXAK;     //使能IIC中断并处于传送模式，且不发送ACK信号
 writeb(temp, i2c_imx->base + IMX_I2C_I2CR);
 return result;
}

static void i2c_imx_stop(struct imx_i2c_struct *i2c_imx)
{
 unsigned int temp = 0;

 if (!i2c_imx->stopped) {
  /* Stop I2C transaction */
  dev_dbg(&i2c_imx->adapter.dev, "<%s>\n", __func__);
  temp = readb(i2c_imx->base + IMX_I2C_I2CR);
  temp &= ~(I2CR_MSTA | I2CR_MTX);
  writeb(temp, i2c_imx->base + IMX_I2C_I2CR);
 }
 if (cpu_is_mx1()) {
  /*
   * This delay caused by an i.MXL hardware bug.
   * If no (or too short) delay, no "STOP" bit will be generated.
   */
  udelay(i2c_imx->disable_delay);
 }

 if (!i2c_imx->stopped) {
  i2c_imx_bus_busy(i2c_imx, 0);
  i2c_imx->stopped = 1;
 }

 /* Disable I2C controller */
 writeb(0, i2c_imx->base + IMX_I2C_I2CR);
 clk_disable(i2c_imx->clk);
}

static void __init i2c_imx_set_clk(struct imx_i2c_struct *i2c_imx,
       unsigned int rate)
{
 unsigned int i2c_clk_rate;
 unsigned int div;
 int i;

 /* Divider value calculation */
 i2c_clk_rate = clk_get_rate(i2c_imx->clk);
 div = (i2c_clk_rate + rate - 1) / rate;
 if (div < i2c_clk_div[0][0])
  i = 0;
 else if (div > i2c_clk_div[ARRAY_SIZE(i2c_clk_div) - 1][0])
  i = ARRAY_SIZE(i2c_clk_div) - 1;
 else
  for (i = 0; i2c_clk_div[i][0] < div; i++);

 /* Store divider value */
 i2c_imx->ifdr = i2c_clk_div[i][1];

 /*
  * There dummy delay is calculated.
  * It should be about one I2C clock period long.
  * This delay is used in I2C bus disable function
  * to fix chip hardware bug.
  */
 i2c_imx->disable_delay = (500000U * i2c_clk_div[i][0]
  + (i2c_clk_rate / 2) - 1) / (i2c_clk_rate / 2);

 /* dev_dbg() can't be used, because adapter is not yet registered */
#ifdef CONFIG_I2C_DEBUG_BUS
 printk(KERN_DEBUG "I2C: <%s> I2C_CLK=%d, REQ DIV=%d\n",
  __func__, i2c_clk_rate, div);
 printk(KERN_DEBUG "I2C: <%s> IFDR[IC]=0x%x, REAL DIV=%d\n",
  __func__, i2c_clk_div[i][1], i2c_clk_div[i][0]);
#endif
}

static irqreturn_t i2c_imx_isr(int irq, void *dev_id)
{
 struct imx_i2c_struct *i2c_imx = dev_id;
 unsigned int temp;

 temp = readb(i2c_imx->base + IMX_I2C_I2SR);
 if (temp & I2SR_IIF) {
  /* save status register */
  i2c_imx->i2csr = temp;
  temp &= ~I2SR_IIF;
  writeb(temp, i2c_imx->base + IMX_I2C_I2SR);
  wake_up(&i2c_imx->queue);
  return IRQ_HANDLED;
 }

 return IRQ_NONE;
}

static int i2c_imx_write(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs)
{
 int i, result;

 dev_dbg(&i2c_imx->adapter.dev, "<%s> write slave address: addr=0x%x\n",
  __func__, msgs->addr << 1);

 /* write slave address */
 writeb(msgs->addr << 1, i2c_imx->base + IMX_I2C_I2DR);
 result = i2c_imx_trx_complete(i2c_imx);
 if (result)
  return result;
 result = i2c_imx_acked(i2c_imx);
 if (result)
  return result;
 dev_dbg(&i2c_imx->adapter.dev, "<%s> write data\n", __func__);

 /* write data */
 for (i = 0; i < msgs->len; i++) {
  dev_dbg(&i2c_imx->adapter.dev,
   "<%s> write byte: B%d=0x%X\n",
   __func__, i, msgs->buf[i]);
  writeb(msgs->buf[i], i2c_imx->base + IMX_I2C_I2DR);
  result = i2c_imx_trx_complete(i2c_imx);
  if (result)
   return result;
  result = i2c_imx_acked(i2c_imx);
  if (result)
   return result;
 }
 return 0;
}

static int i2c_imx_read(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs)
{
 int i, result;
 unsigned int temp;

 dev_dbg(&i2c_imx->adapter.dev,
  "<%s> write slave address: addr=0x%x\n",
  __func__, (msgs->addr << 1) | 0x01);

 /* write slave address 写从地址来寻址设备*/
 writeb((msgs->addr << 1) | 0x01, i2c_imx->base + IMX_I2C_I2DR);
 result = i2c_imx_trx_complete(i2c_imx);
 if (result)
  return result;
 result = i2c_imx_acked(i2c_imx);
 if (result)
  return result;

 dev_dbg(&i2c_imx->adapter.dev, "<%s> setup bus\n", __func__);

 /* setup bus to read data */
 temp = readb(i2c_imx->base + IMX_I2C_I2CR);
 temp &= ~I2CR_MTX;        //转换为读取模式
 if (msgs->len - 1)    //如果要读取的信息只有一个字节长度则不产生ACK信号
  temp &= ~I2CR_TXAK;
 /* I2CR_TXAK
  *Transmit acknowledge enable. Specifies the value driven onto SDA during acknowledge cycles for both master and
  *slave receivers.
  *Note: Writing TXAK applies only when the I2C bus is a receiver.
         * 0 An acknowledge signal is sent to the bus at the ninth clock bit after receiving one byte of data.
         * 1 No acknowledge signal response is sent (that is, the acknowledge bit = 1).
  */
 writeb(temp, i2c_imx->base + IMX_I2C_I2CR);     //注意此是还没有真正的开始传输数据     
 readb(i2c_imx->base + IMX_I2C_I2DR); /* dummy read */                  //目的是激活数据传输
 /*  DataSheet解释：
  In master-receive mode, reading the data register (I2C.I2DR) allows a read to occur and initiates the next
  byte to be received.
  */

 dev_dbg(&i2c_imx->adapter.dev, "<%s> read data\n", __func__);

 /* read data */
 for (i = 0; i < msgs->len; i++) {
  result = i2c_imx_trx_complete(i2c_imx); //等待第一个字节传输完毕 如果一个字节传送完毕后才会向下执行(这里理解起来可能有一点点难度)
  //原因在于当控制器的数据寄存器有完整的数据后才会产行中断，而只有产生了中断等待队列才会被唤醒，进程才能得以向下执行
  if (result)
   return result;
  if (i == (msgs->len - 1)) {                 //如果是最后一个字节且已经传输完则发送一个停止信号
   /* It must generate STOP before read I2DR to prevent
      controller from generating another clock cycle */
   dev_dbg(&i2c_imx->adapter.dev,
    "<%s> clear MSTA\n", __func__);
   temp = readb(i2c_imx->base + IMX_I2C_I2CR);
   temp &= ~(I2CR_MSTA | I2CR_MTX);
   writeb(temp, i2c_imx->base + IMX_I2C_I2CR);
   i2c_imx_bus_busy(i2c_imx, 0);
   i2c_imx->stopped = 1;
  } else if (i == (msgs->len - 2)) {          //如果是倒数第二个字节且已经传输完毕则告诉控制器下一个字节传输完毕后不产生ACK信号
   dev_dbg(&i2c_imx->adapter.dev,
    "<%s> set TXAK\n", __func__);
   temp = readb(i2c_imx->base + IMX_I2C_I2CR);
   temp |= I2CR_TXAK;
   writeb(temp, i2c_imx->base + IMX_I2C_I2CR);
  }
  msgs->buf[i] = readb(i2c_imx->base + IMX_I2C_I2DR);
  dev_dbg(&i2c_imx->adapter.dev,
   "<%s> read byte: B%d=0x%X\n",
   __func__, i, msgs->buf[i]);
 }
 return 0;
}

/**
 * daapter 即当前适配器
 * msgs 要传送的信息
 * num msgs的个数一般情况下为写一个(num = 1)读二个 (num = 2)
 */
static int i2c_imx_xfer(struct i2c_adapter *adapter,
      struct i2c_msg *msgs, int num)
{
 unsigned int i, temp;
 int result;
 struct imx_i2c_struct *i2c_imx = i2c_get_adapdata(adapter);

 dev_dbg(&i2c_imx->adapter.dev, "<%s>\n", __func__);

 /* Start I2C transfer */
 result = i2c_imx_start(i2c_imx);
 if (result)
  goto fail0;

 /* read/write data */
 for (i = 0; i < num; i++) {
  if (i) {
   dev_dbg(&i2c_imx->adapter.dev,
    "<%s> repeated start\n", __func__);
   temp = readb(i2c_imx->base + IMX_I2C_I2CR);
   temp |= I2CR_RSTA;     //让控制器产生一个restart信号
   /* RSTA
      Repeat start. Always reads as 0. Attempting a repeat start without bus mastership causes loss of arbitration.
      0 No repeat start
      1 Generates a repeated START condition
      */
   writeb(temp, i2c_imx->base + IMX_I2C_I2CR);
   result =  i2c_imx_bus_busy(i2c_imx, 1);   // 判断总线是否处于忙状态
   if (result)
    goto fail0;
  }
  dev_dbg(&i2c_imx->adapter.dev,
   "<%s> transfer message: %d\n", __func__, i);
  /* write/read data */
#ifdef CONFIG_I2C_DEBUG_BUS
  temp = readb(i2c_imx->base + IMX_I2C_I2CR);
  dev_dbg(&i2c_imx->adapter.dev, "<%s> CONTROL: IEN=%d, IIEN=%d, "
   "MSTA=%d, MTX=%d, TXAK=%d, RSTA=%d\n", __func__,
   (temp & I2CR_IEN ? 1 : 0), (temp & I2CR_IIEN ? 1 : 0),
   (temp & I2CR_MSTA ? 1 : 0), (temp & I2CR_MTX ? 1 : 0),
   (temp & I2CR_TXAK ? 1 : 0), (temp & I2CR_RSTA ? 1 : 0));
  temp = readb(i2c_imx->base + IMX_I2C_I2SR);
  dev_dbg(&i2c_imx->adapter.dev,
   "<%s> STATUS: ICF=%d, IAAS=%d, IBB=%d, "
   "IAL=%d, SRW=%d, IIF=%d, RXAK=%d\n", __func__,
   (temp & I2SR_ICF ? 1 : 0), (temp & I2SR_IAAS ? 1 : 0),
   (temp & I2SR_IBB ? 1 : 0), (temp & I2SR_IAL ? 1 : 0),
   (temp & I2SR_SRW ? 1 : 0), (temp & I2SR_IIF ? 1 : 0),
   (temp & I2SR_RXAK ? 1 : 0));
#endif
  if (msgs[i].flags & I2C_M_RD)
   result = i2c_imx_read(i2c_imx, &msgs[i]);
  else
   result = i2c_imx_write(i2c_imx, &msgs[i]);
  if (result)
   goto fail0;
 }

fail0:
 /* Stop I2C transfer */
 i2c_imx_stop(i2c_imx);

 dev_dbg(&i2c_imx->adapter.dev, "<%s> exit with: %s: %d\n", __func__,
  (result < 0) ? "error" : "success msg",
   (result < 0) ? result : num);
 return (result < 0) ? result : num;
}

static u32 i2c_imx_func(struct i2c_adapter *adapter)
{
 return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
}

static struct i2c_algorithm i2c_imx_algo = {
 .master_xfer = i2c_imx_xfer,
 .functionality = i2c_imx_func,
};

static int __init i2c_imx_probe(struct platform_device *pdev)
{
 struct imx_i2c_struct *i2c_imx;
 struct resource *res;
 struct imxi2c_platform_data *pdata;
 void __iomem *base;
 resource_size_t res_size;
 int irq;
 int ret;

 dev_dbg(&pdev->dev, "<%s>\n", __func__);

 res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 if (!res) {
  dev_err(&pdev->dev, "can't get device resources\n");
  return -ENOENT;
 }
 irq = platform_get_irq(pdev, 0);
 if (irq < 0) {
  dev_err(&pdev->dev, "can't get irq number\n");
  return -ENOENT;
 }

 pdata = pdev->dev.platform_data;

 if (pdata && pdata->init) {    //进行初始化
  ret = pdata->init(&pdev->dev);
  if (ret)
   return ret;
 }

 res_size = resource_size(res);

 if (!request_mem_region(res->start, res_size, DRIVER_NAME)) {
  ret = -EBUSY;
  goto fail0;
 }

 base = ioremap(res->start, res_size);                    //将控制器的物理地址转换为虚拟地址
 if (!base) {
  dev_err(&pdev->dev, "ioremap failed\n");
  ret = -EIO;
  goto fail1;
 }

 i2c_imx = kzalloc(sizeof(struct imx_i2c_struct), GFP_KERNEL);  //分配一个私有(全局)数据结构
 if (!i2c_imx) {
  dev_err(&pdev->dev, "can't allocate interface\n");
  ret = -ENOMEM;
  goto fail2;
 }

 /* Setup i2c_imx driver structure */
 strcpy(i2c_imx->adapter.name, pdev->name);
 i2c_imx->adapter.owner  = THIS_MODULE;
 i2c_imx->adapter.algo  = &i2c_imx_algo; //<<重点>>（实现了IIC的发送与接收函数）
 i2c_imx->adapter.dev.parent = &pdev->dev;
 i2c_imx->adapter.nr   = pdev->id;
 i2c_imx->irq   = irq;
 i2c_imx->base   = base;
 i2c_imx->res   = res;

 /* Get I2C clock */
 i2c_imx->clk = clk_get(&pdev->dev, "i2c_clk");   //获取IIC的控制时钟
 if (IS_ERR(i2c_imx->clk)) {
  ret = PTR_ERR(i2c_imx->clk);
  dev_err(&pdev->dev, "can't get I2C clock\n");
  goto fail3;
 }

 /* Request IRQ */
 ret = request_irq(i2c_imx->irq, i2c_imx_isr, 0, pdev->name, i2c_imx);             //申请IIC中断（主要处理数据 的发送与接收）
 if (ret) {
  dev_err(&pdev->dev, "can't claim irq %d\n", i2c_imx->irq);
  goto fail4;
 }

 /* Init queue */
 init_waitqueue_head(&i2c_imx->queue);     //初始化等待队列

 /* Set up adapter data */
 i2c_set_adapdata(&i2c_imx->adapter, i2c_imx);          //记录相关设置数据以便以后使用

 /* Set up clock divider */
 if (pdata && pdata->bitrate)
  i2c_imx_set_clk(i2c_imx, pdata->bitrate);             //设置时钟频率  
 else
  i2c_imx_set_clk(i2c_imx, IMX_I2C_BIT_RATE);

 /* Set up chip registers to defaults */
 writeb(0, i2c_imx->base + IMX_I2C_I2CR);
 writeb(0, i2c_imx->base + IMX_I2C_I2SR);

 /* Add I2C adapter */
 ret = i2c_add_numbered_adapter(&i2c_imx->adapter);   //注册IIC设备控制器
 if (ret < 0) {
  dev_err(&pdev->dev, "registration failed\n");
  goto fail5;
 }

 /* Set up platform driver data */
 platform_set_drvdata(pdev, i2c_imx);     // 记录相关数据以便后面使用

 dev_dbg(&i2c_imx->adapter.dev, "claimed irq %d\n", i2c_imx->irq);
 dev_dbg(&i2c_imx->adapter.dev, "device resources from 0x%x to 0x%x\n",
  i2c_imx->res->start, i2c_imx->res->end);
 dev_dbg(&i2c_imx->adapter.dev, "allocated %d bytes at 0x%x \n",
  res_size, i2c_imx->res->start);
 dev_dbg(&i2c_imx->adapter.dev, "adapter name: \"%s\"\n",
  i2c_imx->adapter.name);
 dev_dbg(&i2c_imx->adapter.dev, "IMX I2C adapter registered\n");

 return 0;   /* Return OK */

fail5:
 free_irq(i2c_imx->irq, i2c_imx);
fail4:
 clk_put(i2c_imx->clk);
fail3:
 kfree(i2c_imx);
fail2:
 iounmap(base);
fail1:
 release_mem_region(res->start, resource_size(res));
fail0:
 if (pdata && pdata->exit)
  pdata->exit(&pdev->dev);
 return ret; /* Return error number */
}

static int __exit i2c_imx_remove(struct platform_device *pdev)
{
 struct imx_i2c_struct *i2c_imx = platform_get_drvdata(pdev);
 struct imxi2c_platform_data *pdata = pdev->dev.platform_data;

 /* remove adapter */
 dev_dbg(&i2c_imx->adapter.dev, "adapter removed\n");
 i2c_del_adapter(&i2c_imx->adapter);
 platform_set_drvdata(pdev, NULL);

 /* free interrupt */
 free_irq(i2c_imx->irq, i2c_imx);

 /* setup chip registers to defaults */
 writeb(0, i2c_imx->base + IMX_I2C_IADR);
 writeb(0, i2c_imx->base + IMX_I2C_IFDR);
 writeb(0, i2c_imx->base + IMX_I2C_I2CR);
 writeb(0, i2c_imx->base + IMX_I2C_I2SR);

 /* Shut down hardware */
 if (pdata && pdata->exit)
  pdata->exit(&pdev->dev);

 clk_put(i2c_imx->clk);

 iounmap(i2c_imx->base);
 release_mem_region(i2c_imx->res->start, resource_size(i2c_imx->res));
 kfree(i2c_imx);
 return 0;
}

static struct platform_driver i2c_imx_driver = {
 .remove  = __exit_p(i2c_imx_remove),
 .driver = {
  .name = DRIVER_NAME,
  .owner = THIS_MODULE,
 }
};

static int __init i2c_adap_imx_init(void)
{
 return platform_driver_probe(&i2c_imx_driver, i2c_imx_probe);
}
subsys_initcall(i2c_adap_imx_init);

static void __exit i2c_adap_imx_exit(void)
{
 platform_driver_unregister(&i2c_imx_driver);
}
module_exit(i2c_adap_imx_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Darius Augulis");
MODULE_DESCRIPTION("I2C adapter driver for IMX I2C bus");
MODULE_ALIAS("platform:" DRIVER_NAME);