linux-kernel - Re: [RFC V7 2/2] OPP: Allow "opp-hz" and "opp-microvolt" to contain magic values

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Date:   Wed, 27 Dec 2017 15:36:24 -0600
From:   Rob Herring <robh+dt@...nel.org>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Stephen Boyd <sboyd@...eaurora.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Kevin Hilman <khilman@...nel.org>,
        Viresh Kumar <vireshk@...nel.org>, Nishanth Menon <nm@...com>,
        Rafael Wysocki <rjw@...ysocki.net>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Rajendra Nayak <rnayak@...eaurora.org>,
        Sudeep Holla <sudeep.holla@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [RFC V7 2/2] OPP: Allow "opp-hz" and "opp-microvolt" to contain
 magic values

On Tue, Dec 26, 2017 at 10:45 PM, Viresh Kumar <viresh.kumar@...aro.org> wrote:
> On 26-12-17, 14:23, Rob Herring wrote:
>> >         cpu_opp_table: cpu_opp_table {
>> >                 compatible = "operating-points-v2";
>> >                 opp-shared;
>> >
>> >                 opp00 {
>> >                         opp-hz = /bits/ 64 <208000000>;
>> >                         clock-latency-ns = <500000>;
>> >                         power-domain-opp = <&domain_opp_1>;
>>
>> What is this? opp00 here is not a device. One OPP should not point to
>> another. "power-domain-opp" is only supposed to appear in devices
>> alongside power-domains properties.
>
> There are two type of devices:
>
> A.) With fixed performance state requirements and they will have the
> new "required-opp" property in the device node itself as you said.
>
> B.) Devices which can do DVFS (CPU, MMC, LCD, etc) and those may need
> a different performance state of the domain for their individual OPPs
> and so we can't have this property in the device all the time.
>
> Does this make sense ?

No. From the definition for power-domain-opp

"+- power-domain-opp: This contains phandle to one of the OPP nodes of
the master
+  power domain. This specifies the minimum required OPP of the master
domain for
+  the functioning of the device in this OPP (where this property is present).
+  This property can only be set for a device if the device node contains the
+  "power-domains" property. Also, either all or none of the OPP nodes in an OPP
+  table should have it set."

In the above example, you are violating the next to last sentence.

Though, I'm now confused by what the last sentence means.

Rob