Dan Malek writes: > Graham Stoney wrote: > > > > Dear Embeddees, > > > > I'm wondering if anyone is working on a driver to provide the /dev/watchdog > > interface to the MPC860's on-chip watchdog? > > The difficulty with the on-chip watchdog isn't the driver but > the coordination with boot roms. The "auto-reset" features > of the 8xx (watch dog, bus monitor, etc.) are part of a write once > configuration register. Once disabled, they can't be enabled > again until the processor is reset. > > If the boot rom enables these features (especially the watch dog), > you must service this as part of the Linux kernel processing. You > can't wait around for some application at a later time to determine > it now wants to enable and process the watchdog.
A couple of people mailed me off the list about my query, and as always, Dan's right -- it's nowhere near as simple as I first imagined. The watchdog can't be disabled/reenabled, and its maximum period is only a couple of seconds; there's no guarantee that the kernel will have booted and loaded the application by then, so the watchdog is likely to go off during the boot process. I think this probably puts my plans to use it on hold for now... Thanks, Graham ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/
