本文基于RockPi 4A单板Linux 4.4内核介绍RK3399看门狗(watchdog)的调试方法。
一、驱动文件
RK3399 watchdog用的是新思(Synopsys)的IP,在watchdog驱动程序加载时,会注册misc设备,节点为/dev/watchdog。
驱动文件:drivers/watchdog/dw_wdt.c
二、DTS配置
配置文件:
arch/arm64/boot/dts/rockchip/rk3399.dtsi
watchdog具体配置如下:
watchdog@ff848000 {
compatible = "snps,dw-wdt";
reg = <0x0 0xff848000 0x0 0x100>; ## watchdog寄存器基地址和映射长度
clocks = <&cru PCLK_WDT>; ## watchdog时钟
interrupts = 120 IRQ_TYPE_LEVEL_HIGH 0>; ## watchdog中断号和触发方式
};
三、调试方法
1、关闭看门狗
echo A > watchdog
写入除大写V以外的任意字符,不再喂狗,一段时间后系统会重启。
## drivers/watchdog/watchdog_dev.c
/*
* watchdog_write: writes to the watchdog.
* A write to a watchdog device is defined as a keepalive ping.
* Writing the magic 'V' sequence allows the next close to turn
* off the watchdog (if 'nowayout' is not set).
*/
static ssize_t watchdog_write(struct file *file, const char __user *data,
size_t len, loff_t *ppos)
{
...
}
例:
## 关闭看门狗后,等待一段时间后重启
root@linaro-alip:/dev# echo A > watchdog
[ 1502.302824] dw_wdt: unexpected close, system will reboot soon
root@linaro-alip:/dev# DDR Version 1.20 20190314 ## 系统重启
In
soft reset
2、打开卡门狗
echo V > watchdog
写入大写V,继续喂狗,系统不再重启。
例:
## 打开看门狗
root@linaro-alip:/dev# echo V > watchdog
root@linaro-alip:/dev#
3、CONFIG_WATCHDOG_NOWAYOUT
在watchdog驱动程序中,需要关注宏CONFIG_WATCHDOG_NOWAYOUT。使用如下:
static bool nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, bool, 0);
MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
"(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
如果配置了CONFIG_WATCHDOG_NOWAYOUT,通过echo命令写入任何字符,都不会关闭喂狗。
root@ubuntu:/home/run/code/rockchip-bsp/kernel/arch/arm64/configs# git diff rockchip_linux_defconfig
diff --git a/arch/arm64/configs/rockchip_linux_defconfig b/arch/arm64/configs/rockchip_linux_defconfig
index cfbc7774a15f..80265bdcd598 100644
--- a/arch/arm64/configs/rockchip_linux_defconfig
+++ b/arch/arm64/configs/rockchip_linux_defconfig
CONFIG_WATCHDOG=y
CONFIG_DW_WATCHDOG=y
+CONFIG_WATCHDOG_NOWAYOUT=y
CONFIG_MFD_CROS_EC=y
例:
## 写入任何字符,都不会关闭喂狗
root@linaro-alip:~# echo A > watchdog
root@linaro-alip:~#
注:
使用./build/mk-kernel.sh rockpi4a编译内核时,即使修改了rockchip_linux_defconfig文件,编译时,相关配置也不会生效。需要在编译前make distclean或删除内核根目录下的.config文件后,重新编译内核。
审核编辑 :李倩
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原文标题:Linux驱动之watchdog
文章出处:【微信号:yikoulinux,微信公众号:一口Linux】欢迎添加关注!文章转载请注明出处。
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