linux-kernel - Re: [PATCH v2 08/11] dt-bindings: firmware: arm,scmi: Extend bindings for protocol@13

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Date:   Fri, 21 Jul 2023 13:42:43 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     Cristian Marussi <cristian.marussi@....com>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Stephen Boyd <sboyd@...nel.org>,
        Nikunj Kela <nkela@...cinc.com>,
        Prasad Sodagudi <psodagud@...cinc.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        linux-pm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>, devicetree@...r.kernel.org
Subject: Re: [PATCH v2 08/11] dt-bindings: firmware: arm,scmi: Extend bindings
 for protocol@13

On Wed, 19 Jul 2023 at 17:17, Sudeep Holla <sudeep.holla@....com> wrote:
>
> On Thu, Jul 13, 2023 at 04:17:35PM +0200, Ulf Hansson wrote:
> > The protocol@13 node is describing the performance scaling option for the
> > ARM SCMI interface, as a clock provider. This is unnecessary limiting, as
> > performance scaling is in many cases not limited to switching a clock's
> > frequency.
> >
> > Therefore, let's extend the binding so the interface can be modelled as a
> > generic performance domaintoo. The common way to describe this, is to use
> > the "power-domain" DT bindings, so let's use that.
> >
>
> One thing I forgot to ask earlier is how we can manage different domain IDs
> for perf and power domains which is the case with current SCMI platforms as
> the spec never mandated or can ever mandate the perf and power domains IDs
> to match. They need not be same anyways.

Based upon what you describe above, I have modelled the perf-domain
and the power-domain as two separate power-domain providers.

A consumer device being hooked up to both domains, would specify the
domain IDs in the second power-domain-cell, along the lines of the
below. Then we would use power-domain-names to specify what each
power-domain represents.

power-domains = <&scmi_pd 2>, <&scmi_dvfs 4>;
power-domain-names = "power", "perf";

I hope this makes it clearer!?

Kind regards
Uffe