On Saturday, March 07, 2015 12:06:45 PM Alexandre Belloni wrote:

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

quoted

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.

So question is if we need a separate interrupt handler for that, expecially
since it is shared with the PIT timer anyway.

Seems to me that the simplest way out of this conundrum would be to simply
make the timer's interrupt handler kick the watchdog every once a while and
get rid of the separate watchdog interrupt handler entirely.

While at it, can anyone explain to me please how the suspend state (full
suspend) looks like on that platform?  What's different from the working
state in particular.



-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.