IIC设备驱动程序（十）————IIC总线驱动实现实例

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

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

struct s3c2440_i2c_regs {
    unsigned int iiccon;
    unsigned int iicstat;
    unsigned int iicadd;
    unsigned int iicds;
    unsigned int iiclc;
};

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\n", 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);

}

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;

    s3c2440_i2c_start();

    /* 休眠 */
    timeout = wait_event_timeout(s3c2440_i2c_xfer_data.wait, (s3c2440_i2c_xfer_data.state == STATE_STOP), HZ * 5);
    if (0 == timeout)
    {
        printk("s3c2440_i2c_xfer time out\n");
        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     = ,
    .master_xfer    = s3c2440_i2c_xfer,
    .functionality  = s3c2440_i2c_func,
};

/* 1. 分配/设置i2c_adapter
 */
static struct i2c_adapter s3c2440_i2c_adapter = {
 .name           = "s3c2440_100ask",
 .algo           = &s3c2440_i2c_algo,
 .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; 

    if(iicSt & 0x8){ printk("Bus arbitration failed\n\r"); }

    switch (s3c2440_i2c_xfer_data.state)
    {
        case STATE_START : /* 发出S和设备地址后,产生中断 */
        {
            PRINTK("Start\n");
            /* 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\n");
            /* 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\n");
            /* 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));

    s3c2440_i2c_init();

    request_irq(IRQ_IIC, s3c2440_i2c_xfer_irq, 0, "s3c2440-i2c", NULL);

    init_waitqueue_head(&s3c2440_i2c_xfer_data.wait);

    /* 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");

使用自己编写的IIC总线驱动须配置内核：

Device Drivers
     I2C support
        I2C Hardware Bus support
            < > S3C2410 I2C Driver