summaryrefslogtreecommitdiff
path: root/Documentation/power
diff options
context:
space:
mode:
authorLukasz Luba <lukasz.luba@arm.com>2022-03-21 09:57:27 +0000
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2022-04-13 16:26:18 +0200
commit015f569c4649fe9595ed465dc8e4301d34937f8f (patch)
treee201f8235d24b58a82f730db290cdab70eb7cd11 /Documentation/power
parent16857482b830544f5849daa1048f82d00b68957e (diff)
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.rst20
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
~~~~~~~~~~~~~~~~~~~~~~~~~~~