4700 Watchdog

From Technologic Systems Manuals

The watchdog is manipulated via the ts4700ctl utility. The default INITRD linuxrc autofeeds the watchdog by daemonizing and feeding it in the background via userspace. It can be armed in 3 modes (0 - .4s, 1- 2.7s, 2 - 10.8s). It can be either auto-fed from a background process that continually feeds the watchdog while running (--autofeed option), or via a /dev/watchdog UNIX named pipe which receives single ASCII characters which are written to feed it from another application.

Value Result
0 feed watchdog for another .338s
1 feed watchdog for another 2.706s
2 feed watchdog for another 10.824s
3 disable watchdog

Watchdog by default comes out of reset armed for .338 seconds. TS-BOOTROM firmware feeds for 10.824 and OS code has 10.824 seconds to take over.

You can feed the watchdog from your application by poking a register:

#include <stdio.h>
#include <stdint.h>
#include <fcntl.h>
#include <sys/mman.h>

int main()
{
        int mem;
        volatile uint16_t *syscon;

        mem = open("/dev/mem", O_RDWR|O_SYNC);
        syscon = mmap(0,
                      getpagesize(),
                      PROT_READ|PROT_WRITE,
                      MAP_SHARED,
                      mem,
                      0x80004000);

        for(;;) {
                // This feeds the watchdog for 10s.
                syscon[0x6/2] = 2;
                sleep(5);
        }

        return 0;
}