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| author | Lukasz Luba <lukasz.luba@arm.com> | 2022-03-21 09:57:27 +0000 |
|---|---|---|
| committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2022-04-13 16:26:18 +0200 |
| commit | 015f569c4649fe9595ed465dc8e4301d34937f8f (patch) | |
| tree | e201f8235d24b58a82f730db290cdab70eb7cd11 /Documentation/power | |
| parent | 16857482b830544f5849daa1048f82d00b68957e (diff) | |
| download | lwn-015f569c4649fe9595ed465dc8e4301d34937f8f.tar.gz lwn-015f569c4649fe9595ed465dc8e4301d34937f8f.zip | |
Documentation: EM: Add artificial EM registration description
Add description about new artificial EM registration and use cases.
Update also the documentation with the new .get_cost() callback
description and usage.
Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
Reviewed-by: Ionela Voinescu <ionela.voinescu@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Diffstat (limited to 'Documentation/power')
| -rw-r--r-- | Documentation/power/energy-model.rst | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/Documentation/power/energy-model.rst b/Documentation/power/energy-model.rst index fd29ed2506c0..feb257b7f350 100644 --- a/Documentation/power/energy-model.rst +++ b/Documentation/power/energy-model.rst @@ -123,6 +123,26 @@ allows a platform to register EM power values which are reflecting total power (static + dynamic). These power values might be coming directly from experiments and measurements. +Registration of 'artificial' EM +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +There is an option to provide a custom callback for drivers missing detailed +knowledge about power value for each performance state. The callback +.get_cost() is optional and provides the 'cost' values used by the EAS. +This is useful for platforms that only provide information on relative +efficiency between CPU types, where one could use the information to +create an abstract power model. But even an abstract power model can +sometimes be hard to fit in, given the input power value size restrictions. +The .get_cost() allows to provide the 'cost' values which reflect the +efficiency of the CPUs. This would allow to provide EAS information which +has different relation than what would be forced by the EM internal +formulas calculating 'cost' values. To register an EM for such platform, the +driver must set the flag 'milliwatts' to 0, provide .get_power() callback +and provide .get_cost() callback. The EM framework would handle such platform +properly during registration. A flag EM_PERF_DOMAIN_ARTIFICIAL is set for such +platform. Special care should be taken by other frameworks which are using EM +to test and treat this flag properly. + Registration of 'simple' EM ~~~~~~~~~~~~~~~~~~~~~~~~~~~ |