On 22-12-16, 12:14, Rob Herring wrote:

On Mon, Dec 12, 2016 at 04:26:17PM +0530, Viresh Kumar wrote:

quoted

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 :)

quoted

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