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From:   Rob Herring <robh+dt@kernel.org>
Date:   Fri, 23 Oct 2020 08:34:05 -0500
Message-ID: <CAL_JsqJ0OO68AbML7osOU3fNzJk3NhXYrWVmNwn8mwtNzSuf8g@mail.gmail.com>
Subject: Re: [PATCH 1/2] dt-bindings: arm,scmi: Do not use clocks for SCMI
 performance domains
To:     Sudeep Holla <sudeep.holla@arm.com>
Cc:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        devicetree@vger.kernel.org,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        Viresh Kumar <viresh.kumar@linaro.org>
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On Wed, Oct 21, 2020 at 1:19 PM Sudeep Holla <sudeep.holla@arm.com> wrote:
>
> On Wed, Oct 21, 2020 at 11:20:27AM -0500, Rob Herring wrote:
> > On Tue, Oct 20, 2020 at 3:37 PM Sudeep Holla <sudeep.holla@arm.com> wrote:
> > >
>
> [...]
>
> >
> > When is this not 1 (IOW, you only need this if variable)? How would it
> > be used outside SCMI (given it has a generic name)?
> >
> > > +
> > > +* Property arm,scmi-perf-domain
> >
> [...]
>
> > Really though, why can't you give SCMI a CPUs MPIDR and get its domain?
> >
>
> Now I remembered why we can't use MPIDR. The spec talks about perf domains
> for devices in generic. CPU is just a special device. We will still need
> a mechanism to get device performance domain. So MPIDR idea was dropped to
> keep it uniform across all the devices.

What implications to the binding are there for non-CPU devices? Do
they need more cells? How does this integrate our plethora of other PM
related bindings?

So somewhere in the firmware we're defining device X is domain 0,
device Y is domain 1, etc. Then we do this again in DT. Seems fragile
to define this information twice. I guess that's true for any number
space SCMI defines.

Rob