Re: [RFC PATCH 1/2] PM / OPP: add support to specify phandle of another node for OPP

[Nishanth Menon <nm@ti.com>]

On 15:51-20130731, Stephen Warren wrote:
> On 07/31/2013 08:46 AM, Nishanth Menon wrote:
> ...
> > Let me try to explain since SoCs such as OMAP/AM family dont make life
> > trivial :)..
> > 
> > An legacy example[1][2]
> > 
> > SoC DM explains that the chip is capable of X opps:
> > opp1, 2 - for all devices
> > opp1,2, 3 - if efuse bit X@y is set
> > opp1,2,3,4 - if efuse bit X@y is set AND Board design meets SoC vendors
> > requirements (including additional features A, B is enabled).
> 
> Hopefully the text "board design meets SoC vendors requirements" means
> something like "the board has a big fan capable of dissipating a lot of
> heat" and not "the board manufacturer paid us a lot of money to license
> the 'go faster' feature". The former could well be suitable to represent
> in DT, the latter not.

Nope, these are technical requirements. In my company, these
guidelines are called Power Distribution Network guideline - which
control the IRDrop within reasonable limit, running DPLLs are varied
frequencies have different current draw characteristics, such that noise
limits, cleanup capacitors etc. For boards that dont care too much about
higher frequencies, they tend to skimp a little on caps and board
routing constraints to save on BOM (Bill Of Materials) cost.

I am sure similar constraints do exist in other SoC vendors as well.

-- 
Regards,
Nishanth Menon