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Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/power/energy-model.rst | 24 |
1 files changed, 22 insertions, 2 deletions
diff --git a/Documentation/power/energy-model.rst b/Documentation/power/energy-model.rst index 49549aab41b4..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 ~~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -181,8 +201,8 @@ EM framework:: -> drivers/cpufreq/foo_cpufreq.c - 01 static int est_power(unsigned long *mW, unsigned long *KHz, - 02 struct device *dev) + 01 static int est_power(struct device *dev, unsigned long *mW, + 02 unsigned long *KHz) 03 { 04 long freq, power; 05 |