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

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Message-ID: <20171228043236.GA8652@vireshk-i7>
Date:   Thu, 28 Dec 2017 10:02:36 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Rob Herring <robh+dt@...nel.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 27-12-17, 15:36, Rob Herring wrote:
> 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).

The per-opp thing was mentioned here.

> +  This property can only be set for a device if the device node contains the
> +  "power-domains" property.

This was trying to say something else, though it wasn't clear and so your
concerns.

I wanted to say that the device node or its OPP nodes can have the
"power-domain-opp" property only if the device node has a "power-domains"
property. i.e. you need to have power domain first and then only the
power-domain-opp 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.

Yeah, lets leave it as is as the V8 has changed this significantly and you
already Acked it :)

-- 
viresh