linux操作系统添加看门狗定时

先贴代码
//看门狗物理地址
#define WATCHDOG_BASE             0x01C20000    //基地址
#define BLOCK_SIZE 0X1000    //4K大小

#define rWDOG0_IRQ_EN 0xCA0
#define rWDOG0_IRQ_STA 0xCA4
#define rWDOG0_CTRL 0xCB0
#define rWDOG0_CFG 0xCB4
#define rWDOG0_MODE 0xCB8

/**
*@brief    看门狗和time定时
*/
void *wdog_timer(void *b)
{
int mem_fd = -1;
unsigned char *wdog_map = NULL;
volatile unsigned int *WDOG0_IRQ_EN = NULL;
volatile unsigned int *WDOG0_IRQ_STA = NULL;
volatile unsigned int *WDOG0_CTRL = NULL;
volatile unsigned int *WDOG0_CFG = NULL;
volatile unsigned int *WDOG0_MODE = NULL;
/* open /dev/mem */
if ((mem_fd = open("/dev/mem", O_RDWR | O_CREAT, 0666)) < 0)
{
printf("can't open /dev/mem \n");
exit(-1);
}
/* mmap WDOG0 */
wdog_map = (unsigned char *)mmap(NULL, BLOCK_SIZE, PROT_READ|PROT_WRITE, MAP_SHARED, mem_fd, WATCHDOG_BASE);
close(mem_fd);
if (wdog_map == MAP_FAILED)
{
printf("mmap error %d\n", (int)wdog_map);
exit(-1);
}
// Always use volatile pointer!
WDOG0_IRQ_EN = (volatile unsigned int *)(wdog_map + rWDOG0_IRQ_EN);
WDOG0_IRQ_STA = (volatile unsigned int *)(wdog_map + rWDOG0_IRQ_STA);
WDOG0_CTRL = (volatile unsigned int *)(wdog_map + rWDOG0_CTRL);
WDOG0_CFG = (volatile unsigned int *)(wdog_map + rWDOG0_CFG);
WDOG0_MODE = (volatile unsigned int *)(wdog_map + rWDOG0_MODE);

*(volatile unsigned int *)WDOG0_IRQ_EN = 0x01;
*(volatile unsigned int *)WDOG0_CFG = 0x01;
*(volatile unsigned int *)WDOG0_MODE = 0x30; //看门狗3秒
*(volatile unsigned int *)WDOG0_MODE |= 0X01;
while(1)
{
              //添加自己的程序
         //这里可以加一个判断，如果正常返回，我们就关闭看门狗，否则退出就重启了

if(join_thread_flag == 1)    //如果标志置1，我们就正常返回，关闭看门狗
{
*(volatile unsigned int *)WDOG0_MODE &= ~(0X01 << 0);
*(volatile unsigned int *)WDOG0_IRQ_EN = 0x0;
munmap(0, BLOCK_SIZE);
break;
}
*(volatile unsigned int *)WDOG0_CTRL |= ((0XA57 << 1) | (0X01 << 0)); //喂狗
}
}

mmap系统调用的过程：
void *addr;
addr = mmap(0,0x1000, PROT_READ|PROT_WRITE,
MAP_SHARED, fd, 0);
参数1：如果是0,内核帮找一块内存区域，起始地址是返回值addr
参数2:虚拟内存的大小，0x1000一页（如果申请的内存空间没有对齐，内核会帮我们对齐，会经过一次if/else判断，浪费开销）
参数3：权限
参数4：权限
参数5：fd，将该文件映射到该区域
参数6：映射的偏移量

通过数据手册我查到看门狗的基地址0x01C20C00，但是我们通过mmap函数传参的地址只能传页（4k）的整数倍，所以我传的地址是0x01C20000，然后这个函数给我们返回了一个指针，通过操作这个指针，加上实际物理地址的偏移量，我们就能操作寄存器了，比如我的寄存器rWDOG0_IRQ_EN的偏移量是0xA0，但是我传参时少传了一个0xC00，所以偏移量加上这个即可，就成了0xCA0，以此类推

linux操作系统添加看门狗定时

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