Advanced Configuration and Power Interface Specification

Processor Configuration and Control
Package {
Revision, // Integer (WORD)
RDI[1], // Package
…
RDI[N] // Package
}
Element Object Type Description
Revision Integer The revision number of the _RDI object. Current revision is 0.
(WORD)
RDI[1] Package A variable length Package containing the power resource dependencies of
system level power state 1.
RDI[N] Package A variable length Package containing the power resource dependencies of
system level power state N.
Each RDI[x] sub-Package contains a variable number of References to power resources:
Package {
Resource[0], // Object Reference to a Power Resource Object
…
Resource[M] // Object Reference to a Power Resource Object
}
The Package contains as many RDI packages as there are system level power states in the root
processor container node’s _LPI object. The indexing of LPI power states in this _LPI object
matches the indexing of the RDI packages in the _RDI object. Thus the nth LPI state at the system
level has resource dependencies listed in the nth RDI. Each RDI package returns a list of the power
resource objects (passive or standard power resources) that must be in an OFF state to allow the
platform to enter the LPI state. If a system level LPI does not have any resource dependencies, the
corresponding RDI should be an empty Package.
Both traditional and passive power resources can be listed as dependencies in _RDI. For traditional
power resources, OSPM should ensure that the resource is OFF before requesting a dependent LPI
state. For passive power resources, there are no _ON/_OFF/_STA methods so the only requirement
is to check that the reference count is 0 before requesting a dependent LPI state.
OSPM requirements for ordering between device/power resource transitions and power resource
dependent LPI states differ based on the coordination scheme.
In a platform coordinated system the platform must guarantee correctness and demote the requested
power state to one that will satisfy the resource and processor dependencies. OSPM may use the
dependency info in _RDI as it sees fit, and may select a dependent LPI state even if resources remain
ON.
In an OS initiated system, OSPM must guarantee that all power resources are off (or reference
counts are 0, for passive power resources) before requesting a dependent LPI state.
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