Re: Chassis reset

From: Patrick Williams <patrick@stwcx.xyz>
To: Ed Tanous <ed@tanous.net>
Cc: "openbmc@lists.ozlabs.org" <openbmc@lists.ozlabs.org>,
	Vijay Khemka <vijaykhemka@fb.com>
Subject: Re: Chassis reset
Date: Wed, 23 Sep 2020 15:21:13 -0500	[thread overview]
Message-ID: <20200923202113.GT6152@heinlein> (raw)
In-Reply-To: <CACWQX81tyY1Wo6a8e4hnk3fvinfV-x3ogRK1q1W5cfx28tpfrw@mail.gmail.com>

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On Wed, Sep 23, 2020 at 12:26:58PM -0700, Ed Tanous wrote:
> On Wed, Sep 23, 2020 at 12:10 PM Patrick Williams <patrick@stwcx.xyz> wrote:
> >
> > On Wed, Sep 23, 2020 at 05:45:51AM +0000, Vijay Khemka wrote:
> > >
> > > Yes I have 2 chassis instance xyz/openbmc_project/chassis0 and xyz/openbmc_project/chassis_system0.
> > > Later one is used for AC reset.
> >
> > Can we do a query to see if 'chassis_system0' exists and use it first
> > and then 'chassis0' if not?
> 
> I don't think it's that simple.  The way the dbus APIs are defined,
> one Redfish chassis needs to call the chassis0 path, the other needs
> to call the chassis_system0 path.  We'd need a way to key off which
> one is which.  I haven't seen any entity-manager configs get checked
> in for a "multinode chassis" entity type, so whatever interface we use
> to describe that will probably be what we need to key off to make that
> path distinction.

In Redfish this would be the system path that maps to chassis_system0
and not the chassis path.  In Redfish today, chassis doesn't do a whole
lot except allow you to power cycle the host.  Most of the control is in
System.

> 
> >
> > I think we need to do some enhancement to x86-power-control though also
> > to only create this 'chassis_system0' object if configured.  I believe
> > the current code change you did does it always, even if the
> > systemd-target is empty.
> 
> I keep getting the feeling that xyz/openbmc_project/chassis_system0 is
> just overloading what /xyz/openbmc_project/chassis0 is intended to do,
> x86-power-control just had that already defined, so we went another
> direction.  I wonder if we just need to make the "Can I do a real AC
> reset" configurable, and have it change the behavior of
> /xyz/openbmc_project/chassis0 in that case.

No, these are not overloading each other.  They are vastly different.

host0 + chassis0 make up the 'BIOS/OS control' and '12V power on rails'
portions of host power control respectively.  chassis_system0 controls the
'12v + 5V standby rails' part of the system.  In my opinion, it should
only be present when a system actually allows manipulation of the
standby power, but that isn't how it is currently implemented.

> Also, I'll reiterate that a chassis reset really should be going in a
> separate repo/application from x86-power-control.  x86-power-control
> should be focused on managing the host.

No disagreement from me; that was my recommendation originally.  But,
the current implementation landed there and was accepted by the
maintainer.  I don't honestly think that matters much at a "how should
Redfish APIs map to these dbus objects" perspective though, which is the
current discussion.

-- 
Patrick Williams

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