AMD-Xilinx MPSoC的Watchdog在Linux中使用的简明教程

AMD-Xilinx MPSoC的器件里，提供了内置的Watchdog。在Vivado里选择Watchdog，并在设备树里使能Watchdog，还不能在Linux中正常使用。

pmu-firmware修改

如果要在Linux中使用Watchdog，需要在project-spec/meta-user/recipes-bsp/embeddedsw/pmu-firmware_%.bbappend中添加如下内容：

2021.1以前的版本：

# pmu-firmware_%.bbappend content
YAML_COMPILER_FLAGS_append = " -DENABLE_EM -DENABLE_SCHEDULER"

2022.1及以后的版本：

# pmu-firmware_%.bbappend content
YAML_COMPILER_FLAGS:append = " -DENABLE_EM -DENABLE_SCHEDULER"

Devicetree

检查Devicetree，确保其中的status为"okay"， 也有属性reset-on-timeout。

  watchdog@fd4d0000 {
          clocks = <0x03 0x4b>;
          compatible = "cdns,wdt-r1p2";
          interrupt-parent = <0x04>;
          interrupts = <0x00 0x71 0x01>;
          phandle = <0x76>;
          reg = <0x00 0xfd4d0000 0x00 0x1000>;
          reset-on-timeout;
          status = "okay";
          timeout-sec = <0x3c>;
  };

  watchdog@ff150000 {
          clocks = <0x03 0x70>;
          compatible = "cdns,wdt-r1p2";
          interrupt-parent = <0x04>;
          interrupts = <0x00 0x34 0x01>;
          phandle = <0x77>;
          reg = <0x00 0xff150000 0x00 0x1000>;
          status = "okay";
          timeout-sec = <0x0a>;
  };

启动信息

使用命令“dmesg”检查启动信息，有如下信息。

# dmesg -c | grep watchdog
[  539.845269] watchdog: watchdog0: watchdog did not stop!
[  691.897271] watchdog: watchdog1: watchdog did not stop!
[  702.136679] cdns-wdt ff150000.watchdog: Watchdog timed out. Internal reset not enabled

通过设备节点控制Watchdog

通过设备节点“/dev/watchdog0”可以控制Watchdog。

执行命令“echo s > /dev/watchdog0”，能启动Watchdog，但是没有清狗操作。时间久了，单板会自动重启动。

# echo s > /dev/watchdog0
[  154.773229] watchdog: watchdog0: watchdog did not stop!

# dmesg -c | tail -n 20
[  154.773229] watchdog: watchdog0: watchdog did not stop!

# dmesg -c | tail -n 20

# cat /proc/uptime
193.70 738.72
# Xilinx Zynq MP First Stage Boot Loader
Release 2022.1   Apr 11 2022  -  09:29:50
NOTICE:  BL31: v2.6(release):v1.1-9207-g67ca59c67

执行命令“echo 'V' > /dev/watchdog0”，能停止Watchdog，单板再也不会自动重启动。

# echo s > /dev/watchdog0  && cat /proc/uptime

[ 1850.817370] watchdog: watchdog0: watchdog did not stop!
1850.69 7364.03

# sleep 1

# echo 'V' > /dev/watchdog0 && cat /proc/uptime
1852.40 7370.84

# cat /proc/uptime
1887.11 7509.61
# cat /proc/uptime
1971.67 7847.72
# cat /proc/uptime
2159.96 8600.54

通过应用程序控制Watchdog

Linux也提供了应用程序watchdog控制Watchdog，启动Watchdog并清狗。下面是启动Watchdog的示例。如果由于特殊原因，应用程序watchdog异常退出，就会导致单板复位。下面的例子中，使用kill命令杀死了应用程序watchdog的进程，导致单板复位。

# watchdog -T 10 -t 3 /dev/watchdog0
# ps -A  | grep watchdog
     95 ?        00:00:00 watchdogd
   1159 ?        00:00:00 watchdog

#  cat /proc/uptime
1880.18 7481.78

#  cat /proc/uptime
1895.65 7543.65

# kill -9 1159
# [ 1904.549498] watchdog: watchdog0: watchdog did not stop!

# Xilinx Zynq MP First Stage Boot Loader
Release 2022.1   Apr 11 2022  -  09:29:50
NOTICE:  BL31: v2.6(release):v1.1-9207-g67ca59c67

通过系统脚本启动Watchdog并清狗

Linux也提供系统脚本/etc/init.d/watchdog-init控制Watchdog。
系统脚本/etc/init.d/watchdog-init也使用了应用程序控制Watchdog。如果使用kill命令杀死应用程序watchdog的进程，也会导致单板复位。

# /etc/init.d/watchdog-init start && cat /proc/uptime
Set healthy bit
/etc/init.d/watchdog-init: line 92: /sys/firmware/zynqmp/health_status: Permission denied
Starting WDT
2199.54 8758.78

# ps -A  | grep watchdog
     95 ?        00:00:00 watchdogd
   1110 ?        00:00:00 watchdog

# sleep 5

# /etc/init.d/watchdog-init stop && cat /proc/uptime
Stoping WDT
2204.62 8779.08

# cat /proc/uptime
2299.32 9157.71

# cat /proc/uptime
2628.22 10472.73

参考文档

Cadence WDT Driver

测试单板

KV260 2022.1 BSP