Post LDS review [3/11/2010]

At the Linaro developer summit, all the topics proposed were discussed. A common theme emerging from the discussion was the requirement of some kind of policy manager to take power saving decisions. The policy manager itself is out of scope for the 1105 cycle, but it was decided that we should make sure that all information is exported through common interfaces for someone to implement such policy.

The following changes were made to the initial list of topics.

Dropped

  • PM1.2.2 - ARM idle state -> C-state mapping

    • Driven by ARM, can only commit to starting discussions before this year end
  • PM2.1.1, PM2.1.3 - Add ARM-specific hints, Add SOC-specific and embedded hints
    • We couldn't find any worthwhile additions to powertop hints that aren't already being (planned) to be highlighted by powerdebug
  • PM2.1.2 - Add idle state latencies
    • latencies are gathered through tracepoints and post processed by tools (doesn't make sense to show them in powertop/powerdebug)

Modified

  • PM1.1.2 - Thermal interfaces
    • integrating cpufreq with thermal events is a policy choice and just one of several possible responses to thermal events.
    • it was decided that this policy should be left to SoC/device-specific policy manager for now
    • we will ensure that the current frameworks allow us to export thermal events as required
  • PM3.1.1 - Multi-core decision co-ordination
    • No changes are required to make cpufreq use a single governor for both cores
    • This topic becomes a verification topic to ensure that multi-core SoCs are handled correctly with a single governor thread

Added

Details of PM WG Technical Requirements (draft)

This document expands on the broad focus areas for 1105 for the PM WG.

The Master task list provides other topics of interest to the PM WG and the status of various tasks inside the WG.

PM frameworks

Ref

Feature

Description

Reference

PM1.1

Improve cpufreq for ARM

PM1.1.1

Ondemand governor improvements

Ondemand response is either too slow or it does not maintain the frequency.

PM1.2

Improvde cpuidle for ARM

PM1.2.1

Latency measuring infrastructure

Export latencies of various idle states

PM1.2.2

ARM idle state -> C-state mapping

Adopt consistent language when mapping ARM idle states (across various SoCs) to C-states

PM1.2.3

Governor improvements for realtime usecases

Realtime usecases (high frequency events) are not handled well by cpuidle currently

Tools

Ref

Feature

Description

Reference

PM2.1

Improve powertop

PM2.1.1

Add ARM-specific hints

Add ARM-specific hints to powertop (if any)

PM2.1.2

Add idle state latencies

After adding cpuidle latency tracking infrastructure (display this in powertop or powerdebug?)

PM2.2

Add powerdebug features

PM2.2.1

Visual representation of runtime clock trees

If the clock tree is available using debug_fs, depict it visually (per-peripheral?)

PM2.2.1

Visual representation of runtime regulator trees

Show how the regulator tree is connected (per-peripheral?)

Multi-core

Ref

Feature

Description

Reference

PM3.1

Improve multi-core PM support

PM1.1.1

Multi-core decision co-ordination

Study possibility of deciding target frequency in architecture-common governor code, instead of cpufreq driver

Other tasks dropped currently due to lack of resources

  • Investigation of platform bus-based runtime PM
  • Thermal management as part of cpufreq

Other topics of interest

  • HW with measurement points for various subsystems/regulators

Cycles/1105/TechnicalTopics/PowerManagementCommentary (last modified 2011-03-25 18:15:41)