Re: [PATCH v4 1/3] watchdog: aspeed: Update bootstatus handling

[Andrew Jeffery <andrew@codeconstruct.com.au>]

On Fri, 2024-11-01 at 14:21 -0400, Patrick Williams wrote:
> On Fri, Nov 01, 2024 at 08:11:59PM +0800, Chin-Ting Kuo wrote:
> > The boot status mapping rule follows the latest design guide from
> > the OpenBMC shown as below.
> > https://github.com/openbmc/docs/blob/master/designs/bmc-reboot-cause-update.md#proposed-design
> > - WDIOF_EXTERN1   => system is reset by Software
> > - WDIOF_CARDRESET => system is reset by WDT SoC reset
> > - Others          => other reset events, e.g., power on reset.
> 
> I'm quite surprised that the above is relevant for a kernel driver at
> all.  Isn't "EXTERN1" a name of a real watchdog signal from your
> hardware (my recollection is that there are 2 external watchdogs).

I think you may be referring to WDTRST1 (and WDTRST2) here.

WDIOF_EXTERN1 and WDIOF_EXTERN2 have an unrelated history:

https://github.com/torvalds/linux/blame/master/include/uapi/linux/watchdog.h

>   I
> think the point of this referenced design document was that most
> users
> of BMCs have "EXTERN1" used a for software reset conditions.
> `CARDRESET` should be representing resets by the watchdog itself.

I think this is what Chin-Ting is proposing for the Aspeed driver?

> 
> The purpose of this design proposal was not to require very specific
> changes to individual watchdog drivers, but to align the userspace
> use
> with the best practices already from other watchdog drivers.  I don't
> think the kernel driver should be bending to match a particular
> userspace implementation; you should be exposing the information
> available to your hardware.

I agree with this in principle, but I'm not sure what else is meant to
be done here.

> 
> Having said that, it was known that there would need to be changes to
> the driver because some of these conditions were not adequately
> exposed
> at all.  I'm just still surprised that we're needing to reference
> that
> document as part of these changes.

I think the main question is whether an internal, graceful (userspace-
requested) reset is a reasonable use of WDIOF_EXTERN[12]. My feeling
no. I wonder whether defining a new flag (WDIOF_REBOOT?
WDIOF_GRACEFUL?) in the UAPI would be acceptable?

Andrew