Re: [PATCH V2 0/2] PM / Domains / OPP: Introduce domain-performance-state binding

Viresh Kumar
2017-01-02T10:44:12Z

On 22-12-16, 12:14, Rob Herring wrote:
> On Mon, Dec 12, 2016 at 04:26:17PM +0530, Viresh Kumar wrote:
> > Hello,
> >
> > Some platforms have the capability to configure the performance state of
> > their Power Domains. The performance levels are represented by positive
> > integer values, a lower value represents lower performance state.
> >
> > We had some discussions about it in the past on the PM list [1], which is
> > followed by discussions during the LPC. The outcome of all that was that we
> > should extend Power Domain framework to support active state power management
> > as well.
> >
> > The power-domains until now were only concentrating on the idle state
> > management of the device and this needs to change in order to reuse the
> > infrastructure of power domains for active state management.
>
> From a h/w perspective, are idle states really different from
> performance states?

Its a tricky question TBH :)

The device is almost powered off during the idle states, while
performance states here are the functioning of the device. I haven't
answered your question well, perhaps I need a more direct question :)

> > To get a complete picture of the proposed plan, following is what we
> > need to do:
> > - Create DT bindings to get domain performance state information for the
> > platforms.
>
> I would do this last so you can evolve things if you're not certain
> about what the bindings should look like. You can always start with
> things in the kernel and add to DT later.

I didn't knew that and it looks like a very good option. I am not sure
if I would like to do that for this series though. Maybe lets discuss
the bindings a bit more and if we aren't able to find a common ground,
I can try code first.

> While in theory we should be able to just "describe the h/w" in DT and

Right.

> develop the Linux side independently, this feels too much like the
> bindings are just evolving with Linux needs.

:)

--
viresh