Re: PowerOP 0/3: System power operating point management API

[Pavel Machek <pavel@ucw.cz>]

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Hi!

> PowerOP is a system power parameter management API submitted for
> discussion.  PowerOP writes and reads power "operating points",
> comprised of arbitrary integer-valued values, called power parameters,
> that correspond to registers, clocks, dividers, voltage regulators,
> etc. that may be modified to set a basic power/performance point for the
> system.  The core basically passes an array of integer-valued power
> parameters (with very little additional structure imposed by the core)
> to a platform-specific backend that interprets those values and makes
> the requested adjustments.  PowerOP is intended to leave all power
> policy decisions to higher layers.  An optional sysfs representation of
> power parameters is also available, primarily for diagnostic use.
> 
> PowerOP can be thought of as a layer below cpufreq that actually
> accesses the hardware to make cpu frequency, voltage, core bus, and
> perhaps other modifications to set a power point, leaving cpufreq to
> manage the interfaces based around the "cpu frequency" abstraction, the
> policies and governors that select the frequency, its notifiers, and so
> forth.  An example hooking up support for one cpufreq platform to
> PowerOP is in patch 3/3.
> 
> Depending on the ability of the hardware to make software-controlled
> power/performance adjustments, this may be useful to select custom
> voltages, bus speeds, etc. in desktop/server systems.  Various embedded
> systems have several parameters that can be set.  For example, an XScale
> PXA27x could be considered to have six basic power parameters (mainly
> cpu run mode and memory and bus dividers) that for the most part
> should

This scares me a bit. Is table enough to handle this? I'm afraid that
table will get very large on systems that allow you to do "almost
anything".
								Pavel
-- 
if you have sharp zaurus hardware you don't need... you know my address

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