linux-kernel - Re: [PATCH V3 1/9] PM / OPP: Reword binding supporting multiple regulators per device

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Date:   Mon, 14 Nov 2016 18:13:02 -0800
From:   Stephen Boyd <sboyd@...eaurora.org>
To:     Rob Herring <robh@...nel.org>
Cc:     Viresh Kumar <viresh.kumar@...aro.org>,
        Mark Brown <broonie@...nel.org>,
        Rafael Wysocki <rjw@...ysocki.net>, nm@...com,
        Viresh Kumar <vireshk@...nel.org>,
        linaro-kernel@...ts.linaro.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Vincent Guittot <vincent.guittot@...aro.org>, d-gerlach@...com,
        devicetree@...r.kernel.org
Subject: Re: [PATCH V3 1/9] PM / OPP: Reword binding supporting multiple
 regulators per device

On 11/14, Rob Herring wrote:
> On Fri, Nov 11, 2016 at 08:41:20AM +0530, Viresh Kumar wrote:
> > On 10-11-16, 14:51, Stephen Boyd wrote:
> > > 
> > > No. The supply names (and also clock names/index) should be left
> > > up to the consumer of the OPP table. We don't want to encode any
> > > sort of details like this between the OPP table and the consumer
> > > of it in DT because then it seriously couples the OPP table to
> > > the consumer device. "The binding" in this case that needs to be
> > > updated is the consumer binding, to indicate that it correlated
> > > foo-supply and bar-supply to index 0 and 1 of the OPP table
> > > voltages.
> > 
> > Are you saying that we shall have a property like this then?
> > 
> > diff --git a/Documentation/devicetree/bindings/opp/opp.txt b/Documentation/devicetree/bindings/opp/opp.txt
> > index ee91cbdd95ee..733946df2fb8 100644
> > --- a/Documentation/devicetree/bindings/opp/opp.txt
> > +++ b/Documentation/devicetree/bindings/opp/opp.txt
> > @@ -389,7 +389,10 @@ Example 4: Handling multiple regulators
> >                         compatible = "arm,cortex-a7";
> >                         ...
> >  
> > -                       cpu-supply = <&cpu_supply0>, <&cpu_supply1>, <&cpu_supply2>;
> > +                       vcc0-supply = <&cpu_supply0>;
> > +                       vcc1-supply = <&cpu_supply1>;
> > +                       vcc2-supply = <&cpu_supply2>;
> > +                       opp-supply-names = "vcc0", "vcc1", "vcc2";
> 
> Uh, no. You already have the names in the *-supply properties. Yes, they 
> are a PIA to retrieve compared to a *-names property, but that is the 
> nature of this style of binding.
> 

I think the problem is that Viresh wants the binding to be "self
describing" so that the OPP can be used without a driver knowing
that a supply corresponds to a particular column in the voltage
table. I don't understand that though. Can't we set the supply
names from C code somewhere based on the consumer of the OPPs?
Similar to how we pick the different tables based on fuses?

-- 
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