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

[Stewart Smith]

Alistair Popple <alistair at popple.id.au> writes:
> On Wed, 28 Jan 2015 16:37:02 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?
>> - 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...
>
> I tend to agree, although at the time Jeremy and I couldn't come up with much 
> of an alternative. The problem is that we would like the wdt to be activated 
> before skiboot jumps to the payload so that if the payload fails for some 
> reason we reboot.

We could always have the payload enable it *really* early on.. if we
don't get to the point of being able to make an OPAL call to enable it,
we're probably unlikely to ever actually boot.