On 07/03/2015 at 11:39:39 +0100, Pavel Machek wrote :

quoted

The Atmel watchdog can't be stopped once it's started. This is actually 
very useful so we can reset if suspend or resume failed, the only 
drawback is that you have to wake up from time to time (e.g. by using 
the RTC/RTT) to clear the watchdog and then go back to sleep ASAP.

Yeah. So you do "echo mem > /sys/power/state", and few seconds/minutes
after watchdog kills the system. But you did not ask for dead system,
you asked for suspend.

And while that behaviour is useful for you, I don't think it is
exactly useful behaviour, nor it is the behaviour user would expect.

I think you misunderstood, that is exactly the expected behaviour. This
is hardware defined. Once the watchdog is started, nobody can stop it.
Trying to change the mode register will result in a reset of the SoC.

It is documented in the datasheet and any user wanting another behaviour
is out of luck.

So basically, when using a watchdog, you have to wake up every 15-16s to
restart it.

-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com