Advanced Configuration and Power Interface Specification

Advanced Configuration and Power Interface Specification
8.4.6.3 _PPC (Performance Present Capabilities)
This optional object is a method that dynamically indicates to OSPM the number of performance
states currently supported by the platform. This method returns a number that indicates the _PSS
entry number of the highest performance state that OSPM can use at a given time. OSPM may
choose the corresponding state entry in the _PSS as indicated by the value returned by the _PPC
method or any lower power (higher numbered) state entry in the _PSS.
Arguments:
None
Return Value:
An Integer containing the range of states supported
0 – States 0 through n th state are available (all states available)
1 – States 1 through n th state are available
2 – States 2 through n th state are available
…
n – State n is available only
In order to support dynamic changes of _PPC object, Notify events on the processor object are
allowed. Notify events of type 0x80 will cause OSPM to reevaluate any _PPC objects residing under
the particular processor object notified. This allows AML code to notify OSPM when the number of
supported states may have changed as a result of an asynchronous event (AC insertion/removal,
docked, undocked, and so on).
8.4.6.3.1 OSPM _OST Evaluation
When processing of the _PPC object evaluation completes, OSPM evaluates the _OST object, if
present under the Processor device, to convey _PPC evaluation status to the platform. _OST
arguments specific to _PPC evaluation are described below.
Arguments: (2)
Arg0 – Source Event (Integer) : 0x80
Arg1 – Status Code (Integer) : see below
Return Value:
None
Argument Information:
Arg1 – Status Code
0: Success – OSPM is now using the performance states specified
1: Failure – OSPM has not changed the number of performance states in use.
8.4.6.4 Processor Performance Control Example
Example
This is an example of processor performance control objects in a processor object list.
472 April, 2015 Version 6.0