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I2C驱动开发(1)

已有 611 次阅读2011-5-13 22:24 |个人分类:linux

I2C驱动有两部分组成:I2C总线驱动和I2C设备构成。
     I2C总线驱动是对适配器端的实现,其含有适配器数据结构struct i2c_adapter,适配器算法数据结构struct i2c_algorithm。I2C设备驱动是对设备端的实现和控制,其含有设备驱动结构i2c_driver和设备客户端结构struct i2c_client。
struct i2c_adapter {
        struct module *owner;
        unsigned int id;
        unsigned int class;
        struct i2c_algorithm *algo;//总线通讯数据结构体
        void *algo_data;             //用于保存包含适配器的私有数据结构

 int (*client_register)(struct i2c_client *);//客户端注册函数
 int (*client_unregister)(struct i2c_client *);//客户端注销函数

 struct semaphore bus_lock;
 struct semaphore clist_lock;
 int timeout;
 int retries;         //重试次数
 struct device dev;      //适配器设备
 struct class_device class_dev;   //类设备
 int nr;
 struct list_head clients;  //客户端链表
 struct list_head list;  //适配器链表
 char name[I2C_NAME_SIZE];  //适配器名称
 struct completion dev_released;
 struct completion class_dev_released;
};
struct i2c_algorithm {

 int (*master_xfer)(struct i2c_adapter *adap,struct i2c_msg *msgs,
                    int num);                                                       //i2c总线传输函数
 int (*smbus_xfer) (struct i2c_adapter *adap, u16 addr,
                    unsigned short flags, char read_write,
                    u8 command, int size, union i2c_smbus_data * data); //smbus总线传输函数
 int (*slave_send)(struct i2c_adapter *,char*,int);       //适配器为主模式时发送函数
 int (*slave_recv)(struct i2c_adapter *,char*,int);        //适配器为主模式时接收函数
 int (*algo_control)(struct i2c_adapter *, unsigned int, unsigned long);
 u32 (*functionality) (struct i2c_adapter *);                 //适配器支持功能

};以上两个数据结构为总线驱动需要设置并初始化。
struct i2c_driver {

 struct module *owner;
 char name[32];                //驱动名称
 int id;
 unsigned int class;
 unsigned int flags;    //I2C_DF_NOTIFY用于当设备依附或脱离时通知总线
 int (*attach_adapter)(struct i2c_adapter *);//依附适配器函数
 int (*detach_adapter)(struct i2c_adapter *);//脱离适配器函数
 int (*detach_client)(struct i2c_client *);     //脱离客户端函数
 
 int (*command)(struct i2c_client *client,unsigned int cmd, void *arg);
 struct device_driver driver;  //设备驱动结构体
 struct list_head list;   //链表头

};
struct i2c_client {

 unsigned int flags; 
 unsigned short addr;   // 低7为设备地址
 struct i2c_adapter *adapter; //依附的适配器
 struct i2c_driver *driver; //依附的驱动结构
 int usage_count; 
 struct device dev; 
 struct list_head list; //客户端链表
 char name[I2C_NAME_SIZE];//客户端名称
 struct completion released;

};以上两个数据结构为设备驱动需要设置并初始化。
      Intel制定了SMBus标准用于低速通讯。SMBus二线接口与I2C接口非常相似。SMBus也使用一条数据线(SMBDATA)和一条时钟线(SMBCLK)实现通讯。I2C接口和SMBus接口的主要区别是最大和最小时钟速度。SMBCLK必须在10kHz和100kHz之间。SMBCLK和SMBDATA线也需要上拉电阻。3V供电时上拉电阻大于8.5k ,5V供电时上拉电阻大于14k 。SMBus工作电压范围在3V和5V之间,大于2.1V为高电平,低于0.8V为低电平。struct i2c_adapter对应于物理上的一个适配器,而struct i2c_algorithm对应于一套通讯方法。i2c_algorithm提供一些控制适配器发送或接收函数,对于i2c总线需要初始化master_xfer函数,对于smbus总线需要初始化smbus_xfer函数。master_xfer函数是以i2c_msg为单位进行控制的,其结构如下:
struct i2c_msg {

 __u16 addr;  //从设备地址
 __u16 flags;  //动作标志:读或写
#define I2C_M_TEN 0x10 //器件地址是10Bit
#define I2C_M_RD 0x01
#define I2C_M_NOSTART 0x4000 //意味当前i2c_msg不发送start信号
#define I2C_M_REV_DIR_ADDR 0x2000 //把读写标志位反转
#define I2C_M_IGNORE_NAK 0x1000//当前i2c_msg忽略I2C器件的ack和nack信号。
#define I2C_M_NO_RD_ACK  0x0800 //表示在正行读操作时不去ACK
 __u16 len;  //信息长度
 __u8 *buf;  //信息缓冲区首地址
 
};
      i2c_driver和i2c_client用于控制设备驱动方面的结构。当i2c_driver->attach_adapter探测到物理设备后,因为i2c_client对应一个真实的物理设备则把探测到的i2c_client->adapter指向其依附的适配器的struct i2c_adapter 结构,把i2c_client->driver指向其依附的 i2c_driver结构.其注册和注销的函数分别为 i2c_attach_client和i2c_detach_client.
      总线驱动需要定义一个包含 struct i2c_adapter的私有数据结构,用 i2c_adapter->algo_data指向它即可。
在总线驱动中需要探测并初始化适配器,分配一下IO地址和中断资源。
定义并初始化i2c_algorithm,依据总线类型为i2c或是smbus定义 master_xfer或smbus_xfer函数。
以下为2410适配器驱动程序:
#include <linux/config.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/i2c-id.h>
#include <linux/init.h>
#include <linux/time.h>
#include <linux/interrupt.h>
#include <linux/sched.h>
#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/platform_device.h>
#include <linux/clk.h>
#include <asm/hardware.h>
#include <asm/irq.h>
#include <asm/io.h>
#include <asm/arch/regs-gpio.h>
#include <asm/arch/regs-iic.h>
#include <asm/arch/iic.h>
/* i2c controller state */
enum s3c24xx_i2c_state {
 STATE_IDLE,
 STATE_START,
 STATE_READ,
 STATE_WRITE,
 STATE_STOP
};
struct s3c24xx_i2c {//适配器结构私有结构
 spinlock_t  lock;
 wait_queue_head_t wait;
 struct i2c_msg  *msg;//信息
 unsigned int  msg_num;//信息数量
 unsigned int  msg_idx;//信息索引
 unsigned int  msg_ptr;//信息操作字节指针
  ////////////////////////以上用于操作信息结构
 enum s3c24xx_i2c_state state;
 void __iomem  *regs;//io内存首地址
 struct clk  *clk;
 struct device  *dev;  //控制器对应设备
 struct resource  *irq;//中断资源
 struct resource  *ioarea;//申请的IO内存
 struct i2c_adapter adap;//适配器结构
};
//1010表明设备为EEPROM
static struct s3c2410_platform_i2c s3c24xx_i2c_default_platform = {//平台驱动数据
 .flags  = 0,
 .slave_addr = 0x10,
 .bus_freq = 100*1000,//I2C总线频率 100K
 .max_freq = 400*1000,//I2C总线最大频率
 .sda_delay = S3C2410_IICLC_SDA_DELAY5 | S3C2410_IICLC_FILTER_ON,//
};
/* s3c24xx_i2c_is2440()
 *
 * return true is this is an s3c2440
*/
static inline int s3c24xx_i2c_is2440(struct s3c24xx_i2c *i2c)
{
 struct platform_device *pdev = to_platform_device(i2c->dev);
 return !strcmp(pdev->name, "s3c2440-i2c");
}
//获取设备的平台设备数据
static inline struct s3c2410_platform_i2c *s3c24xx_i2c_get_platformdata(struct device *dev)
{
 if (dev->platform_data != NULL)
  return (struct s3c2410_platform_i2c *)dev->platform_data;
   //有一种将平台数据赋给dev->platform_data,一般在平台设备结构中初始化 如nand如此
 return &s3c24xx_i2c_default_platform;
}
                                          //完成信息传递且唤醒等待队列对应进程
static inline void s3c24xx_i2c_master_complete(struct s3c24xx_i2c *i2c, int ret)
{
 dev_dbg(i2c->dev, "master_complete %d\n", ret);
 i2c->msg_ptr = 0;
 i2c->msg = NULL;
 i2c->msg_idx ++;//指向下一个信息
 i2c->msg_num = 0;
 if (ret)
  i2c->msg_idx = ret;
 wake_up(&i2c->wait);                   //完成所有信息时唤醒进程
}
static inline void s3c24xx_i2c_disable_ack(struct s3c24xx_i2c *i2c)//禁止响应
{
 unsigned long tmp;
 
 tmp = readl(i2c->regs + S3C2410_IICCON);
 writel(tmp & ~S3C2410_IICCON_ACKEN, i2c->regs + S3C2410_IICCON);
}
static inline void s3c24xx_i2c_enable_ack(struct s3c24xx_i2c *i2c)//使能响应
{
 unsigned long tmp;
 
 tmp = readl(i2c->regs + S3C2410_IICCON);
 writel(tmp | S3C2410_IICCON_ACKEN, i2c->regs + S3C2410_IICCON);
}
static inline void s3c24xx_i2c_disable_irq(struct s3c24xx_i2c *i2c)//关中断
{
 unsigned long tmp;
 
 tmp = readl(i2c->regs + S3C2410_IICCON);
 writel(tmp & ~S3C2410_IICCON_IRQEN, i2c->regs + S3C2410_IICCON);
}
static inline void s3c24xx_i2c_enable_irq(struct s3c24xx_i2c *i2c)//使能中断
{
 unsigned long tmp;
 
 tmp = readl(i2c->regs + S3C2410_IICCON);
 writel(tmp | S3C2410_IICCON_IRQEN, i2c->regs + S3C2410_IICCON);
}
                                                     //起始字节发送
static void s3c24xx_i2c_message_start(struct s3c24xx_i2c *i2c,
          struct i2c_msg *msg)
{
 unsigned int addr = (msg->addr & 0x7f) << 1;//7位从设备地址先发送
 unsigned long stat;
 unsigned long iiccon;
 stat = 0;
 stat |=  S3C2410_IICSTAT_TXRXEN;//使能读写
 if (msg->flags & I2C_M_RD) {//为读?
  stat |= S3C2410_IICSTAT_MASTER_RX;//设置控制为主且读动作
  addr |= 1;      //1为读
 } else  //为写?
  stat |= S3C2410_IICSTAT_MASTER_TX;//设置控制为主且写动作
 if (msg->flags & I2C_M_REV_DIR_ADDR)//切换操作动作
  addr ^= 1;
 s3c24xx_i2c_enable_ack(i2c);//使能响应
 iiccon = readl(i2c->regs + S3C2410_IICCON);
 writel(stat, i2c->regs + S3C2410_IICSTAT);//写入IICSTAT
 
 dev_dbg(i2c->dev, "START: %08lx to IICSTAT, %02x to DS\n", stat, addr);
 writeb(addr, i2c->regs + S3C2410_IICDS);//写入起始数据
 udelay(1);
 dev_dbg(i2c->dev, "iiccon, %08lx\n", iiccon);
 writel(iiccon, i2c->regs + S3C2410_IICCON);//刷新iiccon
 
 stat |=  S3C2410_IICSTAT_START;
 writel(stat, i2c->regs + S3C2410_IICSTAT);//启动开始波形
}
static inline void s3c24xx_i2c_stop(struct s3c24xx_i2c *i2c, int ret)//停止传送动作
{
 unsigned long iicstat = readl(i2c->regs + S3C2410_IICSTAT);
 dev_dbg(i2c->dev, "STOP\n");
 /* stop the transfer */
 iicstat &= ~ S3C2410_IICSTAT_START;
 writel(iicstat, i2c->regs + S3C2410_IICSTAT);//为写操作时发送停止波形
 
 i2c->state = STATE_STOP;                  //i2c总线为停止状态
 
 s3c24xx_i2c_master_complete(i2c, ret);                //唤醒进程
 s3c24xx_i2c_disable_irq(i2c);
}
                             //判断当前信息是否为信息队列中最后一个 1=y
static inline int is_lastmsg(struct s3c24xx_i2c *i2c)
{
 return i2c->msg_idx >= (i2c->msg_num - 1);
}
                            //判断该操作字节是否为信息中的最后一个 1=y
static inline int is_msglast(struct s3c24xx_i2c *i2c)
{
 return i2c->msg_ptr == i2c->msg->len-1;
}
                            //判断该信息字节是否已处理完 1=y
static inline int is_msgend(struct s3c24xx_i2c *i2c)
{
 return i2c->msg_ptr >= i2c->msg->len;
}
                                  //传送动作处理
static int i2s_s3c_irq_nextbyte(struct s3c24xx_i2c *i2c, unsigned long iicstat)
{
 unsigned long tmp;
 unsigned char byte;
 int ret = 0;
 switch (i2c->state) {
 case STATE_IDLE:                               //总线空闲
  dev_err(i2c->dev, "%s: called in STATE_IDLE\n", __FUNCTION__);
  goto out;
  break;
 case STATE_STOP:                               //总线停止
  dev_err(i2c->dev, "%s: called in STATE_STOP\n", __FUNCTION__);
  s3c24xx_i2c_disable_irq(i2c); 
  goto out_ack;
 case STATE_START:
                                     //开始处理信息或下一个信息
  if (iicstat  & S3C2410_IICSTAT_LASTBIT &&
      !(i2c->msg->flags & I2C_M_IGNORE_NAK)) {  //响应未到达 出错!!!!
   
   dev_dbg(i2c->dev, "ack was not received\n");
   s3c24xx_i2c_stop(i2c, -EREMOTEIO);//停止操作
   goto out_ack;
  }
  if (i2c->msg->flags & I2C_M_RD)         //下个消息是读或写操作
   i2c->state = STATE_READ;
  else
   i2c->state = STATE_WRITE;
                                 //是否为最后一个信息的最后一个字节
  if (is_lastmsg(i2c) && i2c->msg->len == 0) {
   s3c24xx_i2c_stop(i2c, 0);          //停止
   goto out_ack;
  }
  if (i2c->state == STATE_READ)           //读
   goto prepare_read;
 case STATE_WRITE:
 retry_write:
  if (!is_msgend(i2c)) {               //信息未处理完?
   byte = i2c->msg->buf[i2c->msg_ptr++];//处理下一字节
   writeb(byte, i2c->regs + S3C2410_IICDS);//写入数据移位寄存器
  
  } else if (!is_lastmsg(i2c)) {         //非最后一个信息?
   dev_dbg(i2c->dev, "WRITE: Next Message\n");
   i2c->msg_ptr = 0;                   //处理下一信息
   i2c->msg_idx ++;
   i2c->msg++;
  
   if (i2c->msg->flags & I2C_M_NOSTART) {//不需起始波形?
    if (i2c->msg->flags & I2C_M_RD) {   //因从写切换到读需起始波形,所以非法
     s3c24xx_i2c_stop(i2c, -EINVAL);
    }
    goto retry_write;
   } else {                          //需要起始波形
    s3c24xx_i2c_message_start(i2c, i2c->msg);//起始波形
    i2c->state = STATE_START;
   }
  } else {                    //一个信息处理完成后停止,以便处理下一个信息
   s3c24xx_i2c_stop(i2c, 0);
  }
  break;
 case STATE_READ:            
 
  if (!(i2c->msg->flags & I2C_M_IGNORE_NAK) &&
      !(is_msglast(i2c) && is_lastmsg(i2c))) { //需要nack信号&&非最后字节&&最后信息
   if (iicstat & S3C2410_IICSTAT_LASTBIT) {//序列读 非最后字节完成后需响应信号
    dev_dbg(i2c->dev, "READ: No Ack\n");
   
    s3c24xx_i2c_stop(i2c, -ECONNREFUSED);//出错 停止
    goto out_ack;
   }
  }
  byte = readb(i2c->regs + S3C2410_IICDS);
  i2c->msg->buf[i2c->msg_ptr++] = byte;//读取数据到信息缓冲区
 prepare_read:
  if (is_msglast(i2c)) {//最后字节?
   if (is_lastmsg(i2c))//最后信息?
    s3c24xx_i2c_disable_ack(i2c);//序列读最后字节读操作无响应
  
  } else if (is_msgend(i2c)) {//信息处理完?
   if (is_lastmsg(i2c)) {//最后信息?
    dev_dbg(i2c->dev, "READ: Send Stop\n");
    s3c24xx_i2c_stop(i2c, 0);//停止且所有信息成功处理完
   } else {
    dev_dbg(i2c->dev, "READ: Next Transfer\n");
    i2c->msg_ptr = 0;//处理下一个信息
    i2c->msg_idx++;
    i2c->msg++;
   }
  }
  break;
 }
 /* acknowlegde the IRQ and get back on with the work */
 out_ack:
 tmp = readl(i2c->regs + S3C2410_IICCON);
 tmp &= ~S3C2410_IICCON_IRQPEND;
 writel(tmp, i2c->regs + S3C2410_IICCON);
 out:
 return ret;
}
                                         //中断处理函数
static irqreturn_t s3c24xx_i2c_irq(int irqno, void *dev_id,
       struct pt_regs *regs)
{
 struct s3c24xx_i2c *i2c = dev_id;
 unsigned long status;
 unsigned long tmp;
 status = readl(i2c->regs + S3C2410_IICSTAT);//读状态寄存器以判断何种原因引起中断
 if (status & S3C2410_IICSTAT_ARBITR) {//总线仲裁失败
  dev_err(i2c->dev, "deal with arbitration loss\n");
 }
 if (i2c->state == STATE_IDLE) {      //i2c总线空闲时
  dev_dbg(i2c->dev, "IRQ: error i2c->state == IDLE\n");
  tmp = readl(i2c->regs + S3C2410_IICCON);
  tmp &= ~S3C2410_IICCON_IRQPEND;    //清除中断标志
  writel(tmp, i2c->regs +  S3C2410_IICCON);
  goto out;
 }
 /* pretty much this leaves us with the fact that we've
  * transmitted or received whatever byte we last sent */
 i2s_s3c_irq_nextbyte(i2c, status);
 out:
 return IRQ_HANDLED;
}
//等待总线空闲
static int s3c24xx_i2c_set_master(struct s3c24xx_i2c *i2c)
{
 unsigned long iicstat;
 int timeout = 400;
 while (timeout-- > 0) {
  iicstat = readl(i2c->regs + S3C2410_IICSTAT);
 
  if (!(iicstat & S3C2410_IICSTAT_BUSBUSY))//总线不忙
   return 0;
  msleep(1);
 }
 dev_dbg(i2c->dev, "timeout: GPEDAT is %08x\n",
  __raw_readl(S3C2410_GPEDAT));
 return -ETIMEDOUT;
}
                                              //实质操作函数
static int s3c24xx_i2c_doxfer(struct s3c24xx_i2c *i2c, struct i2c_msg *msgs, int num)
{
 unsigned long timeout;
 int ret;
 ret = s3c24xx_i2c_set_master(i2c);//等待总线空闲以占用总线
 if (ret != 0) {
  dev_err(i2c->dev, "cannot get bus (error %d)\n", ret);
  ret = -EAGAIN;
  goto out;
 }
 spin_lock_irq(&i2c->lock);
 i2c->msg     = msgs;
 i2c->msg_num = num;
 i2c->msg_ptr = 0;//指向第一字节
 i2c->msg_idx = 0;//指向第一信息
 i2c->state   = STATE_START;
 s3c24xx_i2c_enable_irq(i2c);
 s3c24xx_i2c_message_start(i2c, msgs);//起始字节
 spin_unlock_irq(&i2c->lock);
 
                 //将进程阻塞,若在5MS内信息传完或超时则退出等待唤醒
 timeout = wait_event_timeout(i2c->wait, i2c->msg_num == 0, HZ * 5);
 ret = i2c->msg_idx;
 if (timeout == 0)            //超时退出
  dev_dbg(i2c->dev, "timeout\n");
 else if (ret != num)             //非超时退出两者一定要相等复制出错
  dev_dbg(i2c->dev, "incomplete xfer (%d)\n", ret);
 msleep(1);
 out:
 return ret;
}
                                       //传输函数
static int s3c24xx_i2c_xfer(struct i2c_adapter *adap,
   struct i2c_msg *msgs, int num)
{
 struct s3c24xx_i2c *i2c = (struct s3c24xx_i2c *)adap->algo_data;
 int retry;
 int ret;
 for (retry = 0; retry < adap->retries; retry++) {
  ret = s3c24xx_i2c_doxfer(i2c, msgs, num);
  if (ret != -EAGAIN)
   return ret;
  dev_dbg(i2c->dev, "Retrying transmission (%d)\n", retry);
  udelay(100);
 }
 return -EREMOTEIO;
}
//返回适配器所支持的功能
static u32 s3c24xx_i2c_func(struct i2c_adapter *adap)
{
 return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_PROTOCOL_MANGLING;
}
static struct i2c_algorithm s3c24xx_i2c_algorithm = {//i2c通信方式
 .master_xfer  = s3c24xx_i2c_xfer,//底层传输函数
 .functionality  = s3c24xx_i2c_func,//适配器支持的功能函数
};
static struct s3c24xx_i2c s3c24xx_i2c = {//私有结构
 .lock = SPIN_LOCK_UNLOCKED,
 .wait = __WAIT_QUEUE_HEAD_INITIALIZER(s3c24xx_i2c.wait),
 .adap = {
  .name   = "s3c2410-i2c",
  .owner   = THIS_MODULE,
  .algo   = &s3c24xx_i2c_algorithm,//该适配器的通信方式
  .retries  = 2,
  .class   = I2C_CLASS_HWMON,
 },
};
//返回 tx分频设定值
static int s3c24xx_i2c_calcdivisor(unsigned long clkin, unsigned int wanted,
       unsigned int *div1, unsigned int *divs)
{
 unsigned int calc_divs = clkin / wanted;// 0/100=0
 unsigned int calc_div1;
 if (calc_divs > (16*16))
  calc_div1 = 512;
 else
  calc_div1 = 16;
 calc_divs += calc_div1-1;//15
 calc_divs /= calc_div1;//0
 if (calc_divs == 0)
  calc_divs = 1;
 if (calc_divs > 17)
  calc_divs = 17;
 *divs = calc_divs;//1
 *div1 = calc_div1;//16
 return clkin / (calc_divs * calc_div1);//0
}
//测试设定的频率值是否和要求
static inline int freq_acceptable(unsigned int freq, unsigned int wanted)
{
 int diff = freq - wanted;//-100不合要求?需测试
 return (diff >= -2 && diff <= 2);
}
//为用户制定一个除数为请求频率设置,要么被请求的频率或扫描可以接受频率范围内,直到有发现
static int s3c24xx_i2c_getdivisor(struct s3c24xx_i2c *i2c,
      struct s3c2410_platform_i2c *pdata,
      unsigned long *iicon,
      unsigned int *got)
{
 unsigned long clkin = clk_get_rate(i2c->clk);
 
 unsigned int divs, div1;
 int freq;
 int start, end;
 clkin /= 1000;  //时钟由转换为KHZ单位,为0
    
 dev_dbg(i2c->dev,  "pdata %p, freq %lu %lu..%lu\n",
   pdata, pdata->bus_freq, pdata->min_freq, pdata->max_freq);
 if (pdata->bus_freq != 0) {//时钟频率存在?
  freq = s3c24xx_i2c_calcdivisor(clkin, pdata->bus_freq/1000,
            &div1, &divs);//div1=16 divs=1 freq=0
  if (freq_acceptable(freq, pdata->bus_freq/1000))//测试设定的频率值是否和要求
   goto found;
 }
 //不合要求需查找合适值
 start = (pdata->max_freq == 0) ? pdata->bus_freq : pdata->max_freq;//start =400K
 end = pdata->min_freq;//0
 start /= 1000;//400
 end /= 1000;//0
 /* search loop... */
 for (; start > end; start--) {
  freq = s3c24xx_i2c_calcdivisor(clkin, start, &div1, &divs);
  if (freq_acceptable(freq, start))//当start=2时满足要求
   goto found;
 }
 /* cannot find frequency spec */
 return -EINVAL;
 found:
 *got = freq;//0
 *iicon |= (divs-1);//0
 *iicon |= (div1 == 512) ? S3C2410_IICCON_TXDIV_512 : 0;//tx选择fplk/16时分频值无效
 return 0;
}
//硬件初始化(使能中断 使能响应 设置tx选择fplk/16)
static int s3c24xx_i2c_init(struct s3c24xx_i2c *i2c)
{
 unsigned long iicon = S3C2410_IICCON_IRQEN | S3C2410_IICCON_ACKEN;
 struct s3c2410_platform_i2c *pdata;
 unsigned int freq;
 pdata = s3c24xx_i2c_get_platformdata(i2c->adap.dev.parent);
 s3c2410_gpio_cfgpin(S3C2410_GPE15, S3C2410_GPE15_IICSDA);
 s3c2410_gpio_cfgpin(S3C2410_GPE14, S3C2410_GPE14_IICSCL);//将IO引脚配置为I2C控制引脚
 writeb(pdata->slave_addr, i2c->regs + S3C2410_IICADD);//将从设备地址写到IICADD
 dev_info(i2c->dev, "slave address 0x%02x\n", pdata->slave_addr);
 if (s3c24xx_i2c_getdivisor(i2c, pdata, &iicon, &freq) != 0) {//计算I2C时钟及分频值
  dev_err(i2c->dev, "cannot meet bus frequency required\n");
  return -EINVAL;
 }
 /* todo - check that the i2c lines aren't being dragged anywhere */
 dev_info(i2c->dev, "bus frequency set to %d KHz\n", freq);
 dev_dbg(i2c->dev, "S3C2410_IICCON=0x%02lx\n", iicon);
 
 writel(iicon, i2c->regs + S3C2410_IICCON);//以设置tx选择fplk/16
 /* check for s3c2440 i2c controller  */
 if (s3c24xx_i2c_is2440(i2c)) {
  dev_dbg(i2c->dev, "S3C2440_IICLC=%08x\n", pdata->sda_delay);
  writel(pdata->sda_delay, i2c->regs + S3C2440_IICLC);
 }
 return 0;
}
static void s3c24xx_i2c_free(struct s3c24xx_i2c *i2c)
{
 if (i2c->clk != NULL && !IS_ERR(i2c->clk)) {
  clk_disable(i2c->clk);
  clk_put(i2c->clk);
  i2c->clk = NULL;
 }
 if (i2c->regs != NULL) {
  iounmap(i2c->regs);
  i2c->regs = NULL;
 }
 if (i2c->ioarea != NULL) {
  release_resource(i2c->ioarea);
  kfree(i2c->ioarea);
  i2c->ioarea = NULL;
 }
}
static int s3c24xx_i2c_probe(struct platform_device *pdev)//探测函数
{
 struct s3c24xx_i2c *i2c = &s3c24xx_i2c;
 struct resource *res;
 int ret;
 i2c->dev = &pdev->dev;
 i2c->clk = clk_get(&pdev->dev, "i2c");//从clk链表中查找i2c时钟结构
 if (IS_ERR(i2c->clk)) {
  dev_err(&pdev->dev, "cannot get clock\n");
  ret = -ENOENT;
  goto out;
 }
 dev_dbg(&pdev->dev, "clock source %p\n", i2c->clk);
 clk_enable(i2c->clk);
 res = platform_get_resource(pdev, IORESOURCE_MEM, 0);//获取寄存器资源
 if (res == NULL) {
  dev_err(&pdev->dev, "cannot find IO resource\n");
  ret = -ENOENT;
  goto out;
 }
 
 i2c->ioarea = request_mem_region(res->start, (res->end-res->start)+1,
      pdev->name);
 if (i2c->ioarea == NULL) {
  dev_err(&pdev->dev, "cannot request IO\n");
  ret = -ENXIO;
  goto out;
 }
 i2c->regs = ioremap(res->start, (res->end-res->start)+1);//映射IO内存
 if (i2c->regs == NULL) {
  dev_err(&pdev->dev, "cannot map IO\n");
  ret = -ENXIO;
  goto out;
 }
 dev_dbg(&pdev->dev, "registers %p (%p, %p)\n", i2c->regs, i2c->ioarea, res);
 i2c->adap.algo_data = i2c;//保存封装适配器私有结构的指针
 i2c->adap.dev.parent = &pdev->dev;//平台设备为其父设备
 ret = s3c24xx_i2c_init(i2c);//实际即设置iiccon寄存器
 if (ret != 0)
  goto out;
 /* find the IRQ for this unit (note, this relies on the init call to
  * ensure no current IRQs pending
  */
 res = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
 if (res == NULL) {
  dev_err(&pdev->dev, "cannot find IRQ\n");
  ret = -ENOENT;
  goto out;
 }
 
 ret = request_irq(res->start, s3c24xx_i2c_irq, SA_INTERRUPT,
     pdev->name, i2c);//申请中断函数
 if (ret != 0) {
  dev_err(&pdev->dev, "cannot claim IRQ\n");
  goto out;
 }
 i2c->irq = res;
 dev_dbg(&pdev->dev, "irq resource %p (%ld)\n", res, res->start);
 ret = i2c_add_adapter(&i2c->adap);//注册适配器
 if (ret < 0) {
  dev_err(&pdev->dev, "failed to add bus to i2c core\n");
  goto out;
 }
 platform_set_drvdata(pdev, i2c);//pdev.dev.platform_data = i2c
 dev_info(&pdev->dev, "%s: S3C I2C adapter\n", i2c->adap.dev.bus_id);
 out:
 if (ret < 0)
  s3c24xx_i2c_free(i2c);
 return ret;
}
static int s3c24xx_i2c_remove(struct platform_device *pdev)
{
 struct s3c24xx_i2c *i2c = platform_get_drvdata(pdev);
 
 if (i2c != NULL) {
  s3c24xx_i2c_free(i2c);
  platform_set_drvdata(pdev, NULL);
 }
 return 0;
}
#ifdef CONFIG_PM
static int s3c24xx_i2c_resume(struct platform_device *dev)
{
 struct s3c24xx_i2c *i2c = platform_get_drvdata(dev);
 if (i2c != NULL)
  s3c24xx_i2c_init(i2c);
 return 0;
}
#else
#define s3c24xx_i2c_resume NULL
#endif
static struct platform_driver s3c2410_i2c_driver = {//2410平台驱动结构
 .probe  = s3c24xx_i2c_probe,
 .remove  = s3c24xx_i2c_remove,
 .resume  = s3c24xx_i2c_resume,
 .driver  = {
  .owner = THIS_MODULE,
  .name = "s3c2410-i2c",
 },
};
static struct platform_driver s3c2440_i2c_driver = {
 .probe  = s3c24xx_i2c_probe,
 .remove  = s3c24xx_i2c_remove,
 .resume  = s3c24xx_i2c_resume,
 .driver  = {
  .owner = THIS_MODULE,
  .name = "s3c2440-i2c",
 },
};
static int __init i2c_adap_s3c_init(void)//IIC适配器作为平台设备
{
 int ret;
 ret = platform_driver_register(&s3c2410_i2c_driver);
 if (ret == 0) {
  ret = platform_driver_register(&s3c2440_i2c_driver);
  if (ret)
   platform_driver_unregister(&s3c2410_i2c_driver);
 }
 return ret;
}
static void __exit i2c_adap_s3c_exit(void)//注销平台设备
{
 platform_driver_unregister(&s3c2410_i2c_driver);
 platform_driver_unregister(&s3c2440_i2c_driver);
}
module_init(i2c_adap_s3c_init);
module_exit(i2c_adap_s3c_exit);
MODULE_DESCRIPTION("S3C24XX I2C Bus driver");
MODULE_AUTHOR("Ben Dooks, <ben@simtec.co.uk>");
MODULE_LICENSE("GPL");
 
本文来自CSDN博客,转载请标明出处:http://blog.csdn.net/yd4330152763132/archive/2010/02/11/5306446.aspx

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