dth11模块调试问题

static void dht11_start(void)
{
    //此处bug
    gpiod_direction_output(dht11_data_pin, GPIOD_OUT_LOW);
    mdelay(18);
    gpiod_direction_output(dht11_data_pin, GPIOD_OUT_HIGH);
    udelay(40);    
    gpiod_direction_input(dht11_data_pin);
}

static void dth11_start(void){
    //启动信号 
    gpiod_direction_output(dth11_pin,GPIOD_OUT_HIGH);
    udelay(2);
    gpiod_set_value(dth11_pin,0);
    mdelay(18);//18ms的低脉冲。40us的高脉冲
    gpiod_set_value(dth11_pin,1);
    udelay(40);
    gpio_direction_input(dth11_pin);
    udelay(2);
}

static int dht11_read_byte(unsigned char *buf)
{
    int i;
    int us = 0;
    unsigned char data = 0;
    int timeout_us = 200;
    u64 pre, last, last2;
    int ns;
    int j;
    
    for (i = 0; i <8; i++)
    {
        /* 现在是低电平 */
        /* 等待高电平 */
        timeout_us = 400;
        us = 0;
        while (!gpiod_get_value(dht11_data_pin) && --timeout_us)
        {
            udelay(1);
            us++;
        }
        if (!timeout_us)
        {
            printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
            return -1;
        }
        us_low_array[us_low_index++] = us;

        /* 现在是高电平 */
        /* 等待低电平,累加高电平的时间 */
        timeout_us = 20000000;
        us = 0;
        
        //last2 = ktime_get_boot_ns();
        //for (j = 0; j < 23; j++)
        udelay(40);

        if (gpiod_get_value(dht11_data_pin))
        {
            /* get bit 1 */
            data = (data << 1) | 1;

            /* 当前位的高电平未结束, 等待 */
            timeout_us = 400;
            us = 0;
            while (gpiod_get_value(dht11_data_pin) && --timeout_us)
            {
                udelay(1);
                us++;
            }
            if (!timeout_us)
            {
                printk("%s %s line %d\n", __FILE__, __FUNCTION__, __LINE__);
                return -1;
            }
            
        }
        else
        {
            /* get bit 0 */
            data = (data << 1) | 0;
        }
    }

    *buf = data;
    return 0;
}