2440内核如何实现1ms延时甚至更短?
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);