at91sam9: watchdog: period

[Jiří Prchal]

On 19.5.2015 11:14, Boris Brezillon wrote:
>
> There's a difference between your heartbeat (the frequency you
> refresh/reset your watchdog) and the watchdog expiration time (here set
> to 16 secs).
> We usually set the heartbeat to 1/2 or 1/4 the expiration time, so that
> we're (almost) sure we can reset the watchdog before its expiration.
>
>
I'm confused. Why need kernel to know the time in witch userspace process will reset watchdog?
And how to change watchdog expiration time?