[Skiboot] [PATCH 3/3] ipmi/wdt: Add ipmi watchdog timer support

[Benjamin Herrenschmidt]

On Wed, 2015-01-28 at 16:37 +1100, Stewart Smith wrote:
> Alistair Popple <alistair at popple.id.au> writes:
> > Add support for an ipmi watchdog timer. This patch will cause the
> > system to be reset if opal_run_pollers() isn't called for more than
> > about 60 seconds.
> >
> > The timer is reset just prior to running the payload. It is the
> > responsibility of the payload to ensure either opal_run_pollers() is
> > called frequently enough or to disable the watchdog timer by sending
> > appropriate ipmi commands.
> 
> I'm a little uncomfortable in changing what is essentially an ABI here
> without having the payload explicitly enable the WDT.
> 
> I worry about:
> - existing payloads
>   - will current payloads behave correctly? Do we have anything that
>     will currently make sure opal_run_pollers() is called frequently?

Not necessarily. I think we put a kthread in recent kernels to do it but
otherwise, we are utterly dependent on having hvc console call at a
reasonably regular interval.

> - different ABI for payload kernel versus host kernel. If payload
>   (i.e. petitboot environment) disables the watchdog timer, then we'll
>   have different behavior if booted as payload versus as petitboot.
> - some concern about really low power modes and having to muck with
>   this.
> 
> I think I'd prefer us to have to enable the watchdog explicitly...
> 
> Ben, your thoughts?