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Re: [PATCH 01/16] PM / OPP: Add 'supply-names' binding

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  Re: [PATCH 01/16] PM / OPP: Add 'supply-names' binding Stephen Boyd <sboyd@codeaurora.org> - 2015-10-16 02:30 +0200
    Re: [PATCH 01/16] PM / OPP: Add 'supply-names' binding Viresh Kumar <viresh.kumar@linaro.org> - 2015-10-16 08:10 +0200
      Re: [PATCH 01/16] PM / OPP: Add 'supply-names' binding Stephen Boyd <sboyd@codeaurora.org> - 2015-10-16 21:20 +0200
        Re: [PATCH 01/16] PM / OPP: Add 'supply-names' binding Viresh Kumar <viresh.kumar@linaro.org> - 2015-10-17 06:20 +0200

#1248273 — Re: [PATCH 01/16] PM / OPP: Add 'supply-names' binding

On 09/14, Rob Herring wrote:
> On 09/11/2015 07:01 AM, Viresh Kumar wrote:
> > Regulators already have stable DT bindings, wherein the consumer (of
> > supplies) will have following for each regulator/supply.
> > 
> > <name>-supply: <phandle to the regulator node>;
> > 
> > Current OPP bindings extend above, by transforming it into a list of
> > phandles. But we missed the <name> string, which is used to identify the
> > regulator.
> > 
> > And looking from regulators perspective, having two different ways of
> > specifying regulators doesn't seem like a step forward, it also means we
> > have to update every single device binding. And things will become
> > complex.
> > 
> > Another way to support multiple regulators per device (in OPP V2
> > bindings) is to leave regulator consumer bindings as is, and create a
> > 'supply-names' property in the opp-table node, which will contain a list
> > of strings. The names in this list shall match 'name' from the
> > '<name>-supply' strings present in the device node.
> > 
> > The strings in this list also specify the order in which values must be
> > present in 'opp-microvolt' and 'opp-microamp' properties.
> > 
> > Cc: Mark Brown <broonie@kernel.org>
> > Cc: devicetree@vger.kernel.org
> > Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
> > ---
> >  Documentation/devicetree/bindings/opp/opp.txt | 26 +++++++++++++++++++-------
> >  1 file changed, 19 insertions(+), 7 deletions(-)
> > 
> > diff --git a/Documentation/devicetree/bindings/opp/opp.txt b/Documentation/devicetree/bindings/opp/opp.txt
> > index 0cb44dc21f97..8759bc4783ed 100644
> > --- a/Documentation/devicetree/bindings/opp/opp.txt
> > +++ b/Documentation/devicetree/bindings/opp/opp.txt
> > @@ -69,6 +69,13 @@ This describes the OPPs belonging to a device. This node can have following
> >  - compatible: Allow OPPs to express their compatibility. It should be:
> >    "operating-points-v2".
> >  
> > +- supply-names: This is a required property, only if multiple supplies are
> > +  available for the device. Otherwise it is optional.
> > +
> > +  This list is used to pass names of all the device supplies. The order of names
> > +  present here is important, as that should match the order in which values are
> > +  present in 'opp-microvolt' and 'opp-microamp' properties.
> > +
> 
> What if we have a 2nd device and supply rail? For example, what if the
> L2$ has a separate rail from the cores but is linked to the OPPs.

I'm lost why we need this property at all. What happened to using

 opp-microvolt-0 = <1 2 3>;
 opp-microvolt-1 = <1>;
 opp-microvolt-2 = <3 4 5>;
 etc.

That seems to avoid any problem with 3 vs. 1 element properties
combined into one large array. Having supply-names seems too
brittle and would tie us to a particular OPP user's decision to
call supplies by some name.

Also, I've seen devices that are split across two power domains.
These devices aren't CPUs, but they are other devices including
L2 caches. So we're going to need either multiple regulator
support or multiple "power domain at a particular performance
levels" support somehow.

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#1248359

On 15-10-15, 17:22, Stephen Boyd wrote:
> I'm lost why we need this property at all. What happened to using
> 
>  opp-microvolt-0 = <1 2 3>;
>  opp-microvolt-1 = <1>;
>  opp-microvolt-2 = <3 4 5>;
>  etc.

Perhaps you are confusing this with the bindings we came up for
picking right voltage levels based on the cuts/version of the hardware
we are running on. The problem that Lee Jones mentioned and that can
be used in your case as well.

> That seems to avoid any problem with 3 vs. 1 element properties
> combined into one large array.

That's not the problem I was trying to solve here.

> Having supply-names seems too
> brittle and would tie us to a particular OPP user's decision to
> call supplies by some name.

No. The name has to match the <name>-supply property present in the
device's node, that's why we need this property :)

> Also, I've seen devices that are split across two power domains.
> These devices aren't CPUs, but they are other devices including
> L2 caches. So we're going to need either multiple regulator
> support or multiple "power domain at a particular performance
> levels" support somehow.

Right, that's a good example of why we need multi-regulator support :)

-- 
viresh
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#1249093

On 10/16, Viresh Kumar wrote:
> On 15-10-15, 17:22, Stephen Boyd wrote:
> > I'm lost why we need this property at all. What happened to using
> > 
> >  opp-microvolt-0 = <1 2 3>;
> >  opp-microvolt-1 = <1>;
> >  opp-microvolt-2 = <3 4 5>;
> >  etc.
> 
> Perhaps you are confusing this with the bindings we came up for
> picking right voltage levels based on the cuts/version of the hardware
> we are running on. The problem that Lee Jones mentioned and that can
> be used in your case as well.

Isn't that what this patch series is for?

> 
> > That seems to avoid any problem with 3 vs. 1 element properties
> > combined into one large array.
> 
> That's not the problem I was trying to solve here.

What problem are you trying to solve then?

> 
> > Having supply-names seems too
> > brittle and would tie us to a particular OPP user's decision to
> > call supplies by some name.
> 
> No. The name has to match the <name>-supply property present in the
> device's node, that's why we need this property :)

Why does it need to match? Sorry I'm totally lost now.

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#1249261

On 16-10-15, 12:16, Stephen Boyd wrote:
> On 10/16, Viresh Kumar wrote:
> > On 15-10-15, 17:22, Stephen Boyd wrote:
> > > I'm lost why we need this property at all. What happened to using
> > > 
> > >  opp-microvolt-0 = <1 2 3>;
> > >  opp-microvolt-1 = <1>;
> > >  opp-microvolt-2 = <3 4 5>;
> > >  etc.
> > 
> > Perhaps you are confusing this with the bindings we came up for
> > picking right voltage levels based on the cuts/version of the hardware
> > we are running on. The problem that Lee Jones mentioned and that can
> > be used in your case as well.
> 
> Isn't that what this patch series is for?

Hehe, no.

Okay here is the problem statement:

We have two supplies for a device and the device node will have
something like:

name1-supply = <&supply1>;
name2-supply = <&supply2>;

And the OPP node needs to have voltages for both of them:

opp-microvolt = <X1 Y1 Z1>, <X2 Y2 Z2>;

Where XYZ(1) are for supply1 and XYZ(2) are for supply2.

Now we need to identify the supplies for which the values are present
here and their order as well. How do we do that?

The way I am suggesting is to add a property in opp node which will
keep "name1" and "name2" in it.

-- 
viresh
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