2440内核如何实现1ms延时甚至更短？

[weixin_38093608]

昨天的跑马灯模拟步进电机得驱动现在实现了,但是问题又来了，我使用内核提供得msdelay();函数实现的延时，资料上说内核延时精度只能精确到10ms，但是我用示波器观察下来，数据如下。      msdelay(1);//1ms延时               示波器显示为20ms      msdelay(2);//2ms延时               示波器显示为20ms  (和资料上得10ms好像有差距)      msdelay(10);//10ms延时          示波器显示为30ms      msdelay(20);//20ms延时          示波器显示为50ms      msdelay(30);//30ms延时          示波器显示为70ms      msdelay(40);//40ms延时          示波器显示为90ms     从数据上看好像每增加10ms得延时 实际增加20ms得误差，又或是我的驱动程序有问题？现在要想步进电机正常工作起码要1ms的延时。请问还有什么方法可以达到1ms延时或者更短。     驱动程序如下，请大家帮忙看下：   #include <linux/types.h>#include <linux/ioport.h>#include <linux/fcntl.h>#include <linux/miscdevice.h>#include <linux/sched.h>#include <linux/spinlock.h>#include <linux/errno.h>#include <linux/kernel.h>#include <linux/module.h>#include <linux/slab.h>#include <linux/input.h>#include <linux/init.h>#include <linux/delay.h>#include <linux/interrupt.h>#include <linux/device.h>#include <asm/uaccess.h>#include <asm/system.h>#include <asm/io.h>#include <asm/irq.h>#include <asm/arch/regs-gpio.h>#define DEVICE_NAME  "Led"           //定义设备名#define LED_MAJOR 250                  //手动定义主设备号MODULE_AUTHOR("Peter_zhang");MODULE_DESCRIPTION("S3C2440 LED Driver");MODULE_LICENSE("GPL");static unsigned char m_step[8]={0xef,0xef,0xdf,0xdf,0xbf,0xbf,0x7f,0x7f};//4相6线步进电机时序static unsigned int flag=0;static int flag_1=7;static unsigned long GPFDAT,GPFCON;static int s3c2440_leds_open(struct inode *inode,struct file *file){   /* int i;    for(i=0;i<4;i++)    {        s3c2410_gpio_cfgpin(led_table,led_cfg_table);           }   */     GPFCON=(unsigned long)ioremap(0x56000050,4);//内存映射     GPFDAT=(unsigned long)ioremap(0x56000054,4);     GPFCON |=0x5500; //设在F端口4 5 6 7为输出     return 0;}//cmd 选择延时时间，arg 电机转动方向static int s3c2440_leds_ioctl(struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg){                   if(arg==1)    {               (*(volatile unsigned long *)GPFDAT) =m_step[flag++];      msleep(cmd);      if(flag>7)flag=0;              return 0;    }   else if(arg==0)  {         (*(volatile unsigned long *)GPFDAT) =m_step[flag_1--];      msleep(cmd);      if(flag_1<0)flag_1=7;         return 0;  }else  {    return -EINVAL;  }}//定义s3c2440_led_fops:结构体提供基本函数入口点static struct file_operations s3c2440_leds_fops =   {       .owner =   THIS_MODULE,       .open  =   s3c2440_leds_open,       .ioctl =   s3c2440_leds_ioctl,};//模块加载函数static int __init s3c2440_leds_init(void){   int ret;//注册设备号/* register_chrdev是注册字符设备的函数*/   ret=register_chrdev(LED_MAJOR,DEVICE_NAME,&s3c2440_leds_fops);   if (ret < 0){            printk(DEVICE_NAME " can't register major number\n");            return ret;          }printk(DEVICE_NAME " initialized\n");/*打印出驱动加载成功的信息*/   return 0;}//模块卸载函数static void __exit s3c2440_leds_exit(void){   unregister_chrdev(LED_MAJOR, DEVICE_NAME);}//指定驱动程序的初始化函数和卸载函数module_init(s3c2440_leds_init);module_exit(s3c2440_leds_exit);