linux-kernel - Re: [PATCH v2 09/11] cpufreq: scmi: Add support to parse domain-id using #power-domain-cells

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Message-ID: <CAPDyKFogrwFnz2ZuKE-mLrCQmTCQcrtjhhyzB4CnoVnxAXqKEg@mail.gmail.com>
Date:   Fri, 21 Jul 2023 13:52:17 +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
Subject: Re: [PATCH v2 09/11] cpufreq: scmi: Add support to parse domain-id
 using #power-domain-cells

On Wed, 19 Jul 2023 at 17:24, Sudeep Holla <sudeep.holla@....com> wrote:
>
> On Thu, Jul 13, 2023 at 04:17:36PM +0200, Ulf Hansson wrote:
> > The performance domain-id can be described in DT using the power-domains
> > property or the clock property. The latter is already supported, so let's
> > add support for the power-domains too.
> >
>
> How is this supposed to work for the CPUs ? The CPU power domains are
> generally PSCI on most of the platforms and the one using OSI explicitly
> need to specify the details while ones using PC will not need to. Also they
> can never be performance domains too. So I am not sure if I am following this
> correctly.

Your concerns are certainly correct, I completely forgot about this.
We need to specify what power-domain index belongs to what, by using
power-domain-names in DT. So a CPU node, that has both psci for power
and scmi for performance would then typically look like this:

power-domains = <&CPU_PD0>, <&scmi_dvfs 4>;
power-domain-names = "psci", "scmi";

I will take care of this in the next version - and thanks a lot for
pointing this out!

Kind regards
Uffe