[PATCH] watchdog: Add support for the Avionic Design Xanthos watchdog timer.

[thierry.reding@avionic-design.de (Thierry Reding)]

* Wim Van Sebroeck wrote:
> Hi Thierry,
> 
> > > >> This is the only thing I'm still struggling with: the goal of a watchdog device driver is to make sure that the system reboots when the system isn't stable anymore. So why should you then trigger the interrupt?
> > > >>   
> > > >
> > > > ... because a hard reboot might not be the way he wants to resolve the  
> > > > situation.
> > > 
> > > If your system is unstable then sending a keepalive to the watchdog during
> > > this interrupt is not going to change anything neither... Or am I missing
> > > something?
> > 
> > In this case, writing the timeout value to the watchdog is not actually a
> > keepalive. This is in fact the mechanism used to reset/acknowledge the
> > watchdog's interrupt.
> 
> I'm still puzzled. I have seen a number of watchdog devices that have the option to either reboot the system or generate an interrupt.
> They can be set via toggling the correct bits of some configuration register.
> 
> How does this hardware works? Is there a datasheet available somewhere?

It works exactly the same way. The bit defined by ADX_WDT_CONTROL_nRESET
controls this behaviour. If set, the watchdog will only generate an
interrupt, if cleared (the default) it will reboot the system.

There's currently no real datasheet available. The register definitions at
the top of adx_wdt.c are pretty much all of the documentation we currently
have, I'm afraid.

> Kind regards,
> Wim.

Thierry