/dev/watchdog for onchip MPC860 watchdog?

Raphael Massin massin at col.bsf.alcatel.fr
Wed Oct 20 17:33:32 EST 1999

> I've also been thinking about this...
> If the boot process goes bad, then the interrupt driven watchdog will
> keep getting reset and prevent the watchdog from firing...leading to a
> unrecoverable hang.  So, what's the likely hood of the boot process
> going bad?
> Our application requires downloading new kernels and applications and this
> may
> increase the likely hood that a kernel fails to complete the boot process.
> This idea has a window of vunerability but how much and how likely???
> Maybe the timer can be set longer than the longest bootup time or at least
> until the first daemon gets going?
> jeff


I'm using the watchdog timer on a custom board since several months. To
prevent a CPU reset during the kernel is uncompressing, i prorammed it
to generate a Non Maskable Interrupt instead of system reset. Those NMIs
are handled by a special function in the Linux kernel. This function
can reset the board, using a specific I/O, when too many NMIs occurred
without any watchdog timer (SWSR) servicing.

Today, i refresh the timer in my real time application that is launched
immediately after the kernel init. This scheme must work for any board
launching an appli/real time module after kernel init. For other configurations,
Dan's idea seems perfect.


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