Watchdog使用参考

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1. 概述

Watchdog采用标准的linux 框架提供驱动，上层应用可以设定time out时间，自己来keep alive。

Watchdog默认是关闭的，客户可自行决定是否开启。如果开启建议在主线程中操作，如果在其他线程中操作，Watchdog会随着线程的关闭而关闭。

2. WATCHDOG寄存器

Watchdog Register (Bank = 30)
Index (Absolute)	Mnemonic	Bit	Description
00h (003000h)	REG003000	7:0	Default : 0x00	Access : W
	-	7:1	Reserved.
	WDT_CLR	0	set: to restart Watchdog
02h (003004h)	REG003004	7:0	Default : 0x00	Access : R/W
	-	7:1	Reserved.
	WDT_RST_FLAG	0	assert: Watchdog reset has been occurred. set: to clear
02h (003005h)	REG003005	7:0	Default : 0x09	Access : R/W
	WDT_RST_LEN	7:0	length of Watchdog reset.
03h	REG003006	15:0	Default : 0xFFFF	Access : R/W
	WDT_INT	15:0	Watchdog interrupt period; interrupt asserts when "Watchdog counter [31:16]" is equal to WDT_INT and "Watchdog counter[15:0]" is equal to 0x0000.
04h	REG003008	15:0	Default : 0xFFFF	Access : R/W
	WDT_MAX[15:0]	15:0	Watchdog period maximum value bit[15:0].
05h	REG00300A	15:0	Default : 0xFFFF	Access : R/W
	WDT_MAX[32:16]	15:0	Watchdog period maximum value bit[31:16].

3. WATCHDOG控制

3.1. 打开WATCHDOG

1. kernel增加配置

   Device Drivers --->
       [*] SStar SoC platform drivers --->
           <*>  watchdog driver
   

2. infinity7.dtsi确认有watchdog节点

   1.  watchdog: watchdog {  
   2.      compatible = "sstar, infinity-wdt";  
   3.      reg = <0x0 0x1F006000 0x0 0x40>;  
   4.      status="ok";  
   5.  };
   

3. 保证以上两点后如何确认在kernel中有打开watchdog的支持？

   进入shell后，在/dev路径下会有watchdog设备节点：/dev/watchdog。

   打开/dev/watchdog设备，watchdog将被启动。

   参考代码如下：

   1.  int wdt_fd = -1;
   2.  wdt_fd = open("/dev/watchdog", O_WRONLY);
   3.  if (wdt_fd == -1)
   4.  {
   5.      // fail to open watchdog device
   6.  }
   

3.2. 关闭WATCHDOG

参考代码如下：

1.  #define WDIOS_DISABLECARD 0x0001  
2.  int option = WDIOS_DISABLECARD;   
3.  ioctl(wdt_fd, WDIOC_SETOPTIONS, &option);   
4.  if (wdt_fd != -1)  
5.  {  
6.      close(wdt_fd);  
7.      wdt_fd = -1;    
8.  }

3.3. 设定TIMEOUT

通过标准的IOCTL命令WDIOC_SETTIMEOUT，来设定timeout，单位是second，timeout的时间建议大于5s，参考代码如下：

1.  #define WATCHDOG_IOCTL_BASE 'W'  
2.  #define WDIOC_SETTIMEOUT_IOWR(WATCHDOG_IOCTL_BASE, 6, int)  
3.  int timeout = 20;  //secs.
4.  ioctl(wdt_fd, WDIOC_SETTIMEOUT, &timeout);

3.4. KEEP ALIVE

通过标准的IOCTL命令WDIOC_KEEPALIVE来喂狗，喂狗时间按照设定的timeout来决定，喂狗时间应该比timeout小，参考代码如下：

1.  #define WATCHDOG_IOCTL_BASE 'W'  
2.  #define WDIOC_KEEPALIVE_IOR(WATCHDOG_IOCTL_BASE, 5, int)  
3.  ioctl(wdt_fd, WDIOC_KEEPALIVE, 0);