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Diffstat (limited to 'Documentation/power/energy-model.rst')
| -rw-r--r-- | Documentation/power/energy-model.rst | 22 |
1 files changed, 22 insertions, 0 deletions
diff --git a/Documentation/power/energy-model.rst b/Documentation/power/energy-model.rst index 7af0e1760962..5ac62a7b4b7c 100644 --- a/Documentation/power/energy-model.rst +++ b/Documentation/power/energy-model.rst @@ -84,6 +84,16 @@ CONFIG_ENERGY_MODEL must be enabled to use the EM framework. 2.2 Registration of performance domains ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ +Registration of 'advanced' EM +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The 'advanced' EM gets it's name due to the fact that the driver is allowed +to provide more precised power model. It's not limited to some implemented math +formula in the framework (like it's in 'simple' EM case). It can better reflect +the real power measurements performed for each performance state. Thus, this +registration method should be preferred in case considering EM static power +(leakage) is important. + Drivers are expected to register performance domains into the EM framework by calling the following API:: @@ -103,6 +113,18 @@ to: return warning/error, stop working or panic. See Section 3. for an example of driver implementing this callback, or Section 2.4 for further documentation on this API +Registration of 'simple' EM +~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The 'simple' EM is registered using the framework helper function +cpufreq_register_em_with_opp(). It implements a power model which is tight to +math formula:: + + Power = C * V^2 * f + +The EM which is registered using this method might not reflect correctly the +physics of a real device, e.g. when static power (leakage) is important. + 2.3 Accessing performance domains ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |