Re: Dynanic On-The-Fly Operating points for PowerOP

[Matthew Locke <matt@nomadgs.com>]

Dave,

I think we need to focus on defining a powerop interface that will work 
for all (or as close to all as possible) architectures and devices 
types including embedded, laptop, server.   As discussed in previous 
emails, some of the goals for powerop are:

- Architecture/board independent interface
- Integrate with clk framework (and a voltage framework in the future) 
for SoC/Board register setting abstraction
- Provide a layer that knows the SoC and board specifics about 
relationship between voltage and frequency and setting operating points 
(we call it PM Core)
- Provide a clean interface to build on top of (for cpu freq governors, 
etc).

I think we can defer the discussion around creation of op points from 
userspace, suspend/resume integration and transition notifiers.  Once 
we get the basics submitted we can add features piece by piece.

Rather than continue submitting different powerop patches I would 
encourage you to join in the discussion about the interface.  I think 
Eugeny's latest patches are pretty close to satisfying the points made 
so far.  However, we are eagerly waiting feedback because there always 
tradeoffs that need to be made when trying to satisfy the goals listed 
above.

Thanks

Matt
On Aug 8, 2006, at 11:12 AM, David Singleton wrote:

> The patches provided in the following three emails continue the 
> unified,
>         simplified PowerOp concept of power management.  The patches
>         can be found at:
>
>                 http://source.mvista.com/~dsingleton
>
>                         powerop-core.patch
>                         powerop-cpufreq.patch
>                         powerop-x86-centrino.patch
>
>
>                 The patches break the working PowerOP feature into
>         three logical parts.  The first patch is the powerop-core.patch
>         that adds support for an operating point in the standard linux
>         power management infrastructure (CONFIG_PM) and adds a new
>         function to perform transitioning to operating points other
>         than suspend to memory or disk.
>
>                 The second patch, powerop-cpufreq.patch, adds the 
> cpufreq
>         portion of the patch that makes cpufreq tables a set of PowerOp
>         operating points.
>
>                 The third patch, powerop-x86-centrino.patch, adds
>         operating points for all the centrino-speedstep processors.
>
>
>         This set of patches has changed in the following ways.
>
>         1) The patch is now broken out of the cpufreq code and 
> implements
>         operating points for whatever speedstep-centrino the system
>         detects upon boot.
>
>         2) The naming scheme for operating points has been unified to
>         provide a better interface to the PowerOp power manager daemon.
>         The names range from:
>
>                         highest
>                         high
>                         medhigh
>                         medium
>                         medlow
>                         low
>                         lowest
>
>         PowerOp maps the supported processor frequencies onto this
>         namespace list.  The set of centrino processors it supports 
> have
>         supported sets of between four and six different operating 
> points.
>
>         The PowerOP daemon, coming soon, can simply read the supported
>         set of operating points and make some simple rules based
>         decisions about when to transition to various operating points.
>
>         The goal of a unified name space is to provide a PowerOp 
> manager
>         that runs out of the box, with very little setup by the user.
>
>
>         3) This patch supports the ability to provide dynamic, 
> on-the-fly
>         operating points to the framework via a loadable module.  The
> operating
>         point parameters of frequency, voltage and transition latency
>         can be passed at insmod time to create any new operating point
>         the centrino hardware will support.
>
>
>         I think I finally understand the 'why' of hardware vendors 
> asking
>         for a requirement of dynamic, on the fly, operating points.
>
>         I have two sets of hardware that support a wide range of
>         processor speeds and voltages depending on:
>
>         a) the rotary and dip switch setting of the board (the 
> mainstone).
>
>         or
>
>         b) the revision or stepping of the hardware on the board.
>
>         Certain revs of hardware support different frequencies and
> voltages.
>         Some steppings won't run all the frequencies.
>
>         The hardware vendors want to provide support for all the
>         frequencies and voltages that the system could support,
>         depending on the switch settings or rev of hardware without
>         having to change kernel code and recompile the kernel.
>
>         The new dynamic, on the fly, operating point module will allow
>         for this feature.
>
>
> David
>
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