RK 看门狗 WatchDog

 

看门狗 又叫 watchdog timer 是为了能够防止程序跑飞而使用的一种机制
若系统正常 喂狗的程序会正常的进行 一旦系统出现死机、异常等现象 喂狗会停止 系统在一定的时间内没有收到喂狗 就自动重启 恢复到正常状态
其实就是一个定时器电路 一般有一个输入,叫喂狗,一个输出到MCU的RST端,MCU正常工作的时候,每隔一段时间输出一个信号到喂狗端,给 WDT 清零,
如果超过规定时间不喂狗(一般在程序跑飞时),WDT 定时超过,就会给出一个复位信号到MCU,使MCU复位. 防止MCU死机.

 Platform: RK3288
OS: Android 5.1.1
Kernel: 3.10.0

1.1.设备树 看门狗配置 

dtsi片段并不能说明全部-设备树语法是分层的，因此属性(尤其是status)可能仍会被包含基本SoC的板级.dts覆盖. dtsi文件 

kernel\arch\arm\boot\dts\rk3288-tb_zk_r322_V3.dts

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&watchdog {     status = "okay";     //rockchip,irq = <0>;     rockchip,atboot = <0>; };

kernel\arch\arm\boot\dts\rk3288.dtsi

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watchdog: wdt@2004c000 {     compatible = "rockchip,watch dog";     reg = <0xff800000 0x100>;     clocks = <&pclk_pd_alive>;     clock-names = "pclk_wdt";     interrupts = <GIC_SPI 79 IRQ_TYPE_LEVEL_HIGH>;     rockchip,irq = <1>;     rockchip,timeout = <60>;     rockchip,atboot = <1>;     rockchip,debug = <0>;     status = "disabled"; };

1.2.kernel\drivers\watchdog\rk29_wdt.c　　

a.rk29_wdt_set_heartbeat  定时器设定一个中断的时间间隔maxtime  22s

wdt_clock = devm_clk_get(&pdev->dev, "pclk_wdt");

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/* timeout unit second */ int rk29_wdt_set_heartbeat(int timeout) {     unsigned int count = 0;     unsigned int torr = 0, acc = 1, maxtime = 0;        unsigned int freq = clk_get_rate(wdt_clock);       if (timeout < 1)         return -EINVAL;     //0x80000000 is the max count of watch dog     maxtime = 0x80000000 / freq + 1;     if(timeout > maxtime)         timeout = maxtime;               count = timeout * freq;     count /= 0x10000;       while(acc < count){         acc *= 2;         torr++;     }     if(torr > 15){         torr = 15;     }     DBG("%s:torr:%d, count:%d, maxtime:%d s\n", __func__, torr, count, maxtime);     wdt_writel(torr, RK29_WDT_TORR);     return 0; }

b.rk29_wdt_keepalive 喂狗

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/* functions */ void rk29_wdt_keepalive(void) {     if (wdt_base)         wdt_writel(0x76, RK29_WDT_CRR); }

c. rk29_wdt_probe   中断申请函数request_irq详解

rk29_wdt_proberk29_wdt_probe 中断申请  系统回调函数 

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ret = request_irq(wdt_irq->start, rk29_wdt_irq_handler, 0, pdev->name, pdev);   /* interrupt handler code */   static irqreturn_t rk29_wdt_irq_handler(int irqno, void *param) {     DBG("RK29_wdt:watchdog timer expired (irq)\n");     rk29_wdt_keepalive();     return IRQ_HANDLED; }

 d.rk29_wdt_ioctl

WDIOC_KEEPALIVE :喂狗
WDIOC_SETTIMEOUT :设置超时值
WDIOC_GETTIMEOUT :获取超时值

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static long rk29_wdt_ioctl(struct file *file,   unsigned int cmd,                             unsigned long arg) {     void __user *argp = (void __user *)arg;     int __user *p = argp;     int new_margin;     DBG("%s\n", __func__);     switch (cmd) {     case WDIOC_GETSUPPORT:         return copy_to_user(argp, &rk29_wdt_ident,             sizeof(rk29_wdt_ident)) ? -EFAULT : 0;     case WDIOC_GETSTATUS:     case WDIOC_GETBOOTSTATUS:         return put_user(0, p);     case WDIOC_KEEPALIVE:         DBG("%s:rk29_wdt_keepalive\n", __func__);         rk29_wdt_keepalive();         return 0;     case WDIOC_SETTIMEOUT:         if (get_user(new_margin, p))             return -EFAULT;         if (rk29_wdt_set_heartbeat(new_margin))             return -EINVAL;         rk29_wdt_keepalive();         return put_user(tmr_margin, p);     case WDIOC_GETTIMEOUT:         return put_user(tmr_margin, p);     default:         return -ENOTTY;     } }

1.3.JNI  ioctl系统调用来控制设备

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#define    XH_WATCHDOG                          "/dev/watchdog" #define      WDIOC_APP_WDT_CTL                      100     static void watchdog_close(JNIEnv *env, jobject obj, jint fd) {         write(fd, "V", 1);                   ioctl(fd, WDIOC_APP_WDT_CTL, NULL);                   close(fd); } static void watchdog_feed(JNIEnv *env, jobject obj, jint fd) {         write(fd, "a", 1); } static jint watchdog_open(JNIEnv *env, jobject obj) {         int fd=0;         int timeout=0;                   timeout=40;                   fd=open(XH_WATCHDOG, O_RDWR,0);                   if(fd>0)         {             ioctl(fd, WDIOC_SETTIMEOUT, &timeout);             ioctl(fd, WDIOC_APP_WDT_CTL, &timeout);         }                 return fd; }