How to enable and use watchdog of SP7021

The goal of the document is to illustrate how to enable and use watchdog of SP7021.

As an embedded system, to minimize the use of system resources, SP7021 Linux only enables necessary kernel features by default. Watchdog of SP7021 is not enabled by default. To enable watchdog, first, you need to download source files of SP7021 from GitHub. Second, you need to run kernel menuconfig to enable watchdog drivers. Third, you need to re-build SP7021 Linux images. Finally, you need to build and run an application which activates and feeds watchdog periodically. Please follow the following steps.

1. Download source files of SP7021

Source files of SP7021 can be downloaded from GitHub or Yocto server of SP7021. Refer to https://github.com/sunplus-plus1/SP7021 or 2. HOW TO GET SOURCE FILE AND PACKAGE.

2. Enable watchdog driver

Run make kconfig command in project top folder, or go to linux/kernel folder and run make menuconfig command. When “Linux/arm 5.4.35 Kernel Configuration” menu pops up, please use arrow key to move cursor down to “Device Drivers”. Refer to screenshot below, cursor is moved to “Device Drivers”:

Press <Enter> to enter “Device Driver” sub-menu. Next, move cursor down to “Watchdog Timer Support” and press <Space> or “y” to enable it. Refer to screenshot below, “Watchdog Timer Support” is enabled:

Next, press <Enter> to enter “Watchdog Timer Support” sub-menu. Next, move cursor down to “Sunplus watchdog support” and press <Space> or “y” to enable it. Refer to screenshot below, “Sunplus watchdog support” is enabled:

Finally, move cursor to <Save> button and press <Enter> to save configuration.

3. Build Linux image

Go to project top folder. Run make to build SP7021 Linux images.

4. Boot system

Boot system with the built image. You can find watchdog devices in directory /dev by using ls -l /dev command:

~ # ls -l /dev/watchdog*
crw-rw----    1 root     root       10, 130 Jan  1 00:00 /dev/watchdog
crw-rw----    1 root     root      252,   0 Jan  1 00:00 /dev/watchdog0
~ #

5. Run watchdog setup and feeding application

Refer to the following C example code of watchdog setup and feeding application. The application setups, starts, and then feeds watchdog every 10 seconds. Note that the maximum time-out time of watchdog of SP7021 is now about 11 seconds. Any value higher than 11 is invalid.

watchdog.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <pthread.h>
#include <sys/ioctl.h>

#define WATCHDOG_IOCTL_BASE     'W'
#define WDIOC_SETOPTIONS        _IOR(WATCHDOG_IOCTL_BASE, 4, int)
#define WDIOC_KEEPALIVE         _IOR(WATCHDOG_IOCTL_BASE, 5, int)
#define WDIOC_SETTIMEOUT        _IOWR(WATCHDOG_IOCTL_BASE, 6, int)

#define WDIOS_DISABLECARD       1
#define WDIOS_ENABLECARD        2

int wd_fd;
int wd_feed_time = 8;           // Feed watchdog every 8 second by default.
int wd_timeout = 10;            // Timeout time of watchdog. Reset event occurs if watchdog is not fed within this time.


// A thread for feeding watchdog.
void* feedwdt_thd()
{
	int ret;

	while (1) {
		// Feed (reset) watchdog.
		ret = ioctl(wd_fd, WDIOC_KEEPALIVE, 0);
		if (ret != 0) {
	    		printf("Failed to feed watchdog!\n");
	    		close(wd_fd);
		} else {
	    		printf("Feed watchdog every %d seconds.\n", wd_feed_time);
		}

		sleep(wd_feed_time);
	}
}

int main(void)
{
	pthread_t wd_thread;
	int wd_option;
	char str[10];
	int num = 0;
	int ret;

	// Get file handle of watchdog device.
	wd_fd = open("/dev/watchdog0", O_WRONLY);
	if (wd_fd == -1) {
		perror("watchdog");
		exit(EXIT_FAILURE);
	}

	// Enable wacthdog.
	wd_option = WDIOS_ENABLECARD;
	ret = ioctl(wd_fd, WDIOC_SETOPTIONS, &wd_option);
	if (ret != 0){
		printf("Failed to start watchdog!\n");
		close(wd_fd);
		return -1;
	}

	// Setup timeout time.
	ret = ioctl(wd_fd, WDIOC_SETTIMEOUT, &wd_timeout);
	if (ret != 0){
		printf("Failed to set timeout time!\n");
		close(wd_fd);
		return -1;
	}

	// Create a thread for feeding watchdog.
	ret = pthread_create(&wd_thread, NULL, feedwdt_thd, NULL);
	if (ret< 0)
	printf("Failed to create feeddog thread!\n");

	while (1) {
		printf("Press 'e' to disable watchdog and exit.\n");
		printf("Enter a number for new feed time (default feed time is 8 seconds, timeout time is 10 seconds):\n");
		scanf("%s", str);

		if (!strcmp(str,"e")) {
			// Disable watchdog.
			wd_option = WDIOS_DISABLECARD;
			ret = ioctl(wd_fd, WDIOC_SETOPTIONS, &wd_option);
			if (ret != 0) {
				printf("Failed to stop watchdog!\n");
			}
			printf("Disabled watchdog!\n");
			close(wd_fd);
			break;
		}

		if (strspn(str, "0123456789") == strlen(str)) {
			// Get new feed time.
			num = atoi(str);
			if (num > 0) {
				wd_feed_time = num;
			} else {
				printf("Feed time can not be zero!\n");
			}
		} else {
			printf("Invalid feed time!\n");
		}
	}

	return 0;
}

Reference Makefile (You need to modify CC path):

CC=/home/your_home_dir/your_sp7021_project_folder/crossgcc/arm-linux-gnueabihf/bin/arm-linux-gnueabihf-gcc
LDFLAGS=-lpthread

.PHONY: all clean
all: watchdog

watchdog: watchdog.c
	$(CC) $< -o $@ $(LDFLAGS)

clean:
	rm -f watchdog