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: <20230721143728.GB1092306-robh@kernel.org>
Date:   Fri, 21 Jul 2023 08:37:28 -0600
From:   Rob Herring <robh@...nel.org>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Sudeep Holla <sudeep.holla@....com>,
        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 Fri, Jul 21, 2023 at 01:52:17PM +0200, Ulf Hansson wrote:
> 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";

That is completely backwards. Entries are named based on the consumer 
side. The function of each clock or interrupt for example. Here your 
entries are based on the provider which should be opaque to the 
consumer.

Rob