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

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Date:   Fri, 11 Nov 2016 08:41:20 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Stephen Boyd <sboyd@...eaurora.org>
Cc:     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>, robh@...nel.org,
        d-gerlach@...com, devicetree@...r.kernel.org
Subject: Re: [PATCH V3 1/9] PM / OPP: Reword binding supporting multiple
 regulators per device

On 10-11-16, 14:51, Stephen Boyd wrote:
> On 11/10, Viresh Kumar wrote:
> > On 10-11-16, 16:36, Mark Brown wrote:
> > > On Thu, Nov 10, 2016 at 09:34:40AM +0530, Viresh Kumar wrote:
> > > > On 09-11-16, 14:58, Mark Brown wrote:
> > > > > On Wed, Oct 26, 2016 at 12:02:56PM +0530, Viresh Kumar wrote:
> > > 
> > > > > > +  Entries for multiple regulators shall be provided in the same field separated
> > > > > > +  by angular brackets <>. The OPP binding doesn't provide any provisions to
> > > > > > +  relate the values to their power supplies or the order in which the supplies
> > > > > > +  need to be configured.
> > > 
> > > > > I don't understand how this works.  If we have an unordered list of
> > > > > values to set for regulators how will we make sense of them?
> > > 
> > > > The platform driver is responsible to identify the order and pass it on to the
> > > > OPP core. And the platform driver needs to have that hard coded.
> > > 
> > > That *really* should be in the binding.
> > 
> > Okay, how do you suggest doing that? Will a property like supply-names
> > in the OPP table be fine? Like this:
> > 
> > @@ -369,13 +378,16 @@ 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>;
> >                         operating-points-v2 = <&cpu0_opp_table>;
> >                 };
> >         };
> >  
> >         cpu0_opp_table: opp_table0 {
> >                 compatible = "operating-points-v2";
> > +               supply-names = "vcc0", "vcc1", "vcc2";
> >                 opp-shared;
> > 
> 
> 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";
                        operating-points-v2 = <&cpu0_opp_table>;
                };
        };


-- 
viresh