本文基于RockPi 4A單板Linux 4.4內(nèi)核介紹RK3399看門狗(watchdog)的調(diào)試方法。

一、驅(qū)動(dòng)文件

RK3399 watchdog用的是新思（Synopsys）的IP，在watchdog驅(qū)動(dòng)程序加載時(shí)，會(huì)注冊(cè)misc設(shè)備，節(jié)點(diǎn)為/dev/watchdog。

驅(qū)動(dòng)文件：drivers/watchdog/dw_wdt.c

二、DTS配置

配置文件：
arch/arm64/boot/dts/rockchip/rk3399.dtsi

watchdog具體配置如下：

watchdog@ff848000 {
        compatible = "snps,dw-wdt";
        reg = <0x0 0xff848000 0x0 0x100>; ## watchdog寄存器基地址和映射長(zhǎng)度
        clocks = <&cru PCLK_WDT>; ## watchdog時(shí)鐘
        interrupts =  120 IRQ_TYPE_LEVEL_HIGH 0>; ## watchdog中斷號(hào)和觸發(fā)方式
};

三、調(diào)試方法

1、關(guān)閉看門狗

echo A > watchdog

寫入除大寫V以外的任意字符，不再喂狗，一段時(shí)間后系統(tǒng)會(huì)重啟。

## 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：

## 關(guān)閉看門狗后，等待一段時(shí)間后重啟
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  ## 系統(tǒng)重啟
In
soft reset

2、打開卡門狗

echo V > watchdog

寫入大寫V，繼續(xù)喂狗，系統(tǒng)不再重啟。

例：

## 打開看門狗
root@linaro-alip:/dev# echo V > watchdog
root@linaro-alip:/dev#

3、CONFIG_WATCHDOG_NOWAYOUT

在watchdog驅(qū)動(dòng)程序中，需要關(guān)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，通過(guò)echo命令寫入任何字符，都不會(huì)關(guān)閉喂狗。

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：

## 寫入任何字符，都不會(huì)關(guān)閉喂狗
root@linaro-alip:~# echo A > watchdog
root@linaro-alip:~#

注：

使用./build/mk-kernel.sh rockpi4a編譯內(nèi)核時(shí)，即使修改了rockchip_linux_defconfig文件，編譯時(shí)，相關(guān)配置也不會(huì)生效。需要在編譯前make distclean或刪除內(nèi)核根目錄下的.config文件后，重新編譯內(nèi)核。

審核編輯 ：李倩