Linux I2C总线控制器驱动(S3C2440)

 s3c2440的i2c控制器驱动(精简DIY)，直接上代码，注释很详细：

#include <linux/kernel.h>
#include <linux/module.h>

#include <linux/i2c.h>
#include <linux/init.h>
#include <linux/time.h>
#include <linux/interrupt.h>
#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/err.h>
#include <linux/platform_device.h>
#include <linux/pm_runtime.h>
#include <linux/clk.h>
#include <linux/cpufreq.h>
#include <linux/slab.h>
#include <linux/io.h>
#include <linux/of_i2c.h>
#include <linux/of_gpio.h>
#include <plat/gpio-cfg.h>
#include <mach/regs-gpio.h>

#include <asm/irq.h>

#include <plat/regs-iic.h>
#include <plat/iic.h>

//#define PRINTK printk
#define PRINTK(...) 

enum s3c24xx_i2c_state {
    STATE_IDLE,
    STATE_START,
    STATE_READ,
    STATE_WRITE,
    STATE_STOP
};

//i2c控制器寄存器
struct s3c2440_i2c_regs {
    unsigned int iiccon;
    unsigned int iicstat;
    unsigned int iicadd;
    unsigned int iicds;
    unsigned int iiclc;
};

//i2c数据传输载体
struct s3c2440_i2c_xfer_data {
    struct i2c_msg *msgs;
    int msn_num;
    int cur_msg;
    int cur_ptr;
    int state;
    int err;
    wait_queue_head_t wait;
};

static struct s3c2440_i2c_xfer_data s3c2440_i2c_xfer_data;


static struct s3c2440_i2c_regs *s3c2440_i2c_regs;


static void s3c2440_i2c_start(void)
{
    s3c2440_i2c_xfer_data.state = STATE_START;
    
    if (s3c2440_i2c_xfer_data.msgs->flags & I2C_M_RD) /* 读 */
    {
        s3c2440_i2c_regs->iicds         = s3c2440_i2c_xfer_data.msgs->addr << 1;　
        s3c2440_i2c_regs->iicstat      = 0xb0;    // 主机接收，启动
    }
    else /* 写 */
    {
        s3c2440_i2c_regs->iicds         = s3c2440_i2c_xfer_data.msgs->addr << 1;
        s3c2440_i2c_regs->iicstat    = 0xf0;         // 主机发送，启动
    }
}

static void s3c2440_i2c_stop(int err)
{
    s3c2440_i2c_xfer_data.state = STATE_STOP;
    s3c2440_i2c_xfer_data.err   = err;

    PRINTK("STATE_STOP, err = %d
", err);


    if (s3c2440_i2c_xfer_data.msgs->flags & I2C_M_RD) /* 读 */
    {
        // 下面两行恢复I2C操作，发出P信号
        s3c2440_i2c_regs->iicstat = 0x90;
        s3c2440_i2c_regs->iiccon  = 0xaf;
        ndelay(50);  // 等待一段时间以便P信号已经发出
    }
    else /* 写 */
    {
        // 下面两行用来恢复I2C操作，发出P信号
        s3c2440_i2c_regs->iicstat = 0xd0;
        s3c2440_i2c_regs->iiccon  = 0xaf;
        ndelay(50);  // 等待一段时间以便P信号已经发出
    }

    /* 唤醒 */
    wake_up(&s3c2440_i2c_xfer_data.wait);
    
}

//i2c总线数据传输处理函数
static int s3c2440_i2c_xfer(struct i2c_adapter *adap,
            struct i2c_msg *msgs, int num)
{
    unsigned long timeout;
    
    /* 把num个msg的I2C数据发送出去/读进来 */
    s3c2440_i2c_xfer_data.msgs    = msgs;
    s3c2440_i2c_xfer_data.msn_num = num;
    s3c2440_i2c_xfer_data.cur_msg = 0;
    s3c2440_i2c_xfer_data.cur_ptr = 0;
    s3c2440_i2c_xfer_data.err     = -ENODEV; //确认是否有ack应答

    s3c2440_i2c_start();　//发出start信号，判断read or write

    /* 休眠-等待i2c读写状态改变 */
    timeout = wait_event_timeout(s3c2440_i2c_xfer_data.wait, (s3c2440_i2c_xfer_data.state == STATE_STOP), HZ * 5);　//等待状态成立或5s
    if (0 == timeout)
    {
        printk("s3c2440_i2c_xfer time out
");
        return -ETIMEDOUT;
    }
    else
    {
        return s3c2440_i2c_xfer_data.err;
    }
}

static u32 s3c2440_i2c_func(struct i2c_adapter *adap)
{
    return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_PROTOCOL_MANGLING;
}


static const struct i2c_algorithm s3c2440_i2c_algo = {
//    .smbus_xfer     = ,   //smbus是i2c传输的一个子集,支持的话可以在这里指定处理函数
    .master_xfer    = s3c2440_i2c_xfer,　//传输函数
    .functionality    = s3c2440_i2c_func,
};

/* 1. 分配/设置i2c_adapter
 */
static struct i2c_adapter s3c2440_i2c_adapter = {
 .name             = "s3c2440_sheldon",
 .algo             = &s3c2440_i2c_algo,　//算法函数
 .owner          = THIS_MODULE,
};

static int isLastMsg(void)
{
    return (s3c2440_i2c_xfer_data.cur_msg == s3c2440_i2c_xfer_data.msn_num - 1);
}

static int isEndData(void)
{
    return (s3c2440_i2c_xfer_data.cur_ptr >= s3c2440_i2c_xfer_data.msgs->len);
}

static int isLastData(void)
{
    return (s3c2440_i2c_xfer_data.cur_ptr == s3c2440_i2c_xfer_data.msgs->len - 1);
}

static irqreturn_t s3c2440_i2c_xfer_irq(int irq, void *dev_id)
{
    unsigned int iicSt;
        
     iicSt  = s3c2440_i2c_regs->iicstat;  //读取i2c控制器的状态寄存器，判断是否读写成功

    if(iicSt & 0x8){ printk("Bus arbitration failed

"); }

    switch (s3c2440_i2c_xfer_data.state)
    {
        case STATE_START : /* 发出S和设备地址后,产生中断 */
        {
            PRINTK("Start
");
            /* 如果没有ACK, 返回错误 */
            if (iicSt & S3C2410_IICSTAT_LASTBIT)
            {
                s3c2440_i2c_stop(-ENODEV);
                break;
            }

            if (isLastMsg() && isEndData())
            {
                s3c2440_i2c_stop(0);
                break;
            }

            /* 进入下一个状态 */
            if (s3c2440_i2c_xfer_data.msgs->flags & I2C_M_RD) /* 读 */
            {
                s3c2440_i2c_xfer_data.state = STATE_READ;
                goto next_read;
            }
            else
            {
                s3c2440_i2c_xfer_data.state = STATE_WRITE;
            }    
        }

        case STATE_WRITE:
        {
            PRINTK("STATE_WRITE
");
            /* 如果没有ACK, 返回错误 */
            if (iicSt & S3C2410_IICSTAT_LASTBIT)
            {
                s3c2440_i2c_stop(-ENODEV);
                break;
            }

            if (!isEndData())  /* 如果当前msg还有数据要发送 */
            {
                s3c2440_i2c_regs->iicds = s3c2440_i2c_xfer_data.msgs->buf[s3c2440_i2c_xfer_data.cur_ptr];
                s3c2440_i2c_xfer_data.cur_ptr++;
                
                // 将数据写入IICDS后，需要一段时间才能出现在SDA线上
                ndelay(50);    
                
                s3c2440_i2c_regs->iiccon = 0xaf;        // 恢复I2C传输
                break;                
            }
            else if (!isLastMsg())
            {
                /* 开始处理下一个消息 */
                s3c2440_i2c_xfer_data.msgs++;
                s3c2440_i2c_xfer_data.cur_msg++;
                s3c2440_i2c_xfer_data.cur_ptr = 0;
                s3c2440_i2c_xfer_data.state = STATE_START;
                /* 发出START信号和发出设备地址 */
                s3c2440_i2c_start();
                break;
            }
            else
            {
                /* 是最后一个消息的最后一个数据 */
                s3c2440_i2c_stop(0);
                break;                
            }

            break;
        }

        case STATE_READ:
        {
            PRINTK("STATE_READ
");
            /* 读出数据 */
            s3c2440_i2c_xfer_data.msgs->buf[s3c2440_i2c_xfer_data.cur_ptr] = s3c2440_i2c_regs->iicds;            
            s3c2440_i2c_xfer_data.cur_ptr++;
next_read:
            if (!isEndData()) /* 如果数据没读写, 继续发起读操作 */
            {
                if (isLastData())  /* 如果即将读的数据是最后一个, 不发ack */
                {
                    s3c2440_i2c_regs->iiccon = 0x2f;   // 恢复I2C传输，接收到下一数据时无ACK
                }
                else
                {
                    s3c2440_i2c_regs->iiccon = 0xaf;   // 恢复I2C传输，接收到下一数据时发出ACK
                }                
                break;
            }
            else if (!isLastMsg())
            {
                /* 开始处理下一个消息 */
                s3c2440_i2c_xfer_data.msgs++;
                s3c2440_i2c_xfer_data.cur_msg++;
                s3c2440_i2c_xfer_data.cur_ptr = 0;
                s3c2440_i2c_xfer_data.state = STATE_START;
                /* 发出START信号和发出设备地址 */
                s3c2440_i2c_start();
                break;
            }
            else
            {
                /* 是最后一个消息的最后一个数据 */
                s3c2440_i2c_stop(0);
                break;                                
            }
            break;
        }

        default: break;
    }

    /* 清中断 */
    s3c2440_i2c_regs->iiccon &= ~(S3C2410_IICCON_IRQPEND);

    return IRQ_HANDLED;    
}


/*
 * I2C初始化
 */
static void s3c2440_i2c_init(void)
{
    struct clk *clk;

    clk = clk_get(NULL, "i2c");
    clk_enable(clk);
    
    // 选择引脚功能：GPE15:IICSDA, GPE14:IICSCL
    　　　　s3c_gpio_cfgpin(S3C2410_GPE(14), S3C2410_GPE14_IICSCL);
    s3c_gpio_cfgpin(S3C2410_GPE(15), S3C2410_GPE15_IICSDA);

    /* bit[7] = 1, 使能ACK
     * bit[6] = 0, IICCLK = PCLK/16
     * bit[5] = 1, 使能中断
     * bit[3:0] = 0xf, Tx clock = IICCLK/16
     * PCLK = 50MHz, IICCLK = 3.125MHz, Tx Clock = 0.195MHz
     */
    s3c2440_i2c_regs->iiccon = (1<<7) | (0<<6) | (1<<5) | (0xf);  // 0xaf

    s3c2440_i2c_regs->iicadd  = 0x10;     // S3C24xx slave address = [7:1]
    s3c2440_i2c_regs->iicstat = 0x10;     // I2C串行输出使能(Rx/Tx)
}

static int i2c_bus_s3c2440_init(void)
{
    /* 2. 硬件相关的设置 */
    s3c2440_i2c_regs = ioremap(0x54000000, sizeof(struct s3c2440_i2c_regs));//映射功能寄存器
    
    s3c2440_i2c_init(); //初始化i2c控制器

    request_irq(IRQ_IIC, s3c2440_i2c_xfer_irq, 0, "s3c2440-i2c", NULL);　//申请中断源,加载中断处理函数－s3c2440_i2c_xfer_irq

    init_waitqueue_head(&s3c2440_i2c_xfer_data.wait); //初始化一个等待队列头
    
    /* 3. 注册i2c_adapter */
    i2c_add_adapter(&s3c2440_i2c_adapter);
    
    return 0;
}

static void i2c_bus_s3c2440_exit(void)
{
    i2c_del_adapter(&s3c2440_i2c_adapter);    
    free_irq(IRQ_IIC, NULL);
    iounmap(s3c2440_i2c_regs);
}

module_init(i2c_bus_s3c2440_init);
module_exit(i2c_bus_s3c2440_exit);
MODULE_LICENSE("GPL");

附一份测试程序：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include "i2c-dev.h"


/* i2c_usr_test </dev/i2c-0> <dev_addr> r addr
 * i2c_usr_test </dev/i2c-0> <dev_addr> w addr val
 */

void print_usage(char *file)
{
    printf("%s </dev/i2c-0> <dev_addr> r addr
", file);
    printf("%s </dev/i2c-0> <dev_addr> w addr val
", file);
}

int main(int argc, char **argv)
{
    int fd;
    unsigned char addr, data;
    int dev_addr;
    
    if ((argc != 5) && (argc != 6))
    {
        print_usage(argv[0]);
        return -1;
    }

    fd = open(argv[1], O_RDWR);
    if (fd < 0)
    {
        printf("can't open %s
", argv[1]);
        return -1;
    }

    dev_addr = strtoul(argv[2], NULL, 0);
    if (ioctl(fd, I2C_SLAVE, dev_addr) < 0)
    {    
        /* ERROR HANDLING; you can check errno to see what went wrong */    
        printf("set addr error!
");
        return -1;
    }

    if (strcmp(argv[3], "r") == 0)
    {
        addr = strtoul(argv[4], NULL, 0);
        
        data = i2c_smbus_read_word_data(fd, addr);
            
        printf("data: %c, %d, 0x%2x
", data, data, data);
    }
    else if ((strcmp(argv[3], "w") == 0) && (argc == 6))
    {
        addr = strtoul(argv[4], NULL, 0);
        data = strtoul(argv[5], NULL, 0);
        i2c_smbus_write_byte_data(fd, addr, data);        
    }
    else
    {
        print_usage(argv[0]);
        return -1;
    }
    
    return 0;
}

Make File:

KERN_DIR = /work/system/linux-3.4.2

all:
    make -C $(KERN_DIR) M=`pwd` modules 

clean:
    make -C $(KERN_DIR) M=`pwd` modules clean
    rm -rf modules.order

obj-m    += i2c_bus_s3c2440.o