Advanced Configuration and Power Interface Specification

Advanced Configuration and Power Interface Specification
types of notifications, see Section 5.6.6, “Device Object Notifications”). Notice that a device check
notification from the \_SB node will cause OSPM to re-enumerate the entire tree 1 .
Hardware is not obligated to track the state needed to supply the resulting status; however, this
method must return status concerning the last sleep operation initiated by OSPM. The return values
can be used to provide additional information to OSPM or user.
Arguments: (1)
Arg0 – An Integer containing the value of the sleeping state (1 for S1, 2 for S2, etc.)
Return Value:
A Package containing two Integers containing status and the power supply S-state
Return Value Information
_WAK returns a package with the following format:
Element 0 – An Integer containing a bitfield that represents conditions that occurred during sleep.
0x00000000 – Wake was signaled and was successful
0x00000001 – Wake was signaled but failed due to lack of power
0x00000002 – Wake was signaled but failed due to thermal condition
Other values – Reserved
Element 1 – An Integer containing the power supply S-state.
If non-zero, this is the effective S-state the power supply that was actually entered.
This value is used to detect when the targeted S-state was not entered because of too
much current being drawn from the power supply. For example, this might occur
when some active device’s current consumption pushes the system’s power
requirements over the low power supply mark, thus preventing the deeper system
sleeping state from being entered as desired.
7.5 OSPM usage of _PTS, _TTS, and _WAK
OSPM will invoke _PTS, _TTS,and _WAK in the following order:
1. OSPM decides (through a policy scheme) to place the system into a sleeping state
2. _TTS(Sx) is run, where Sx is the desired sleep state to enter
3. OSPM notifies all native device drivers of the sleep state transition
4. _PTS is run
5. OSPM readies system for the sleep state transition
6. OSPM writes the sleep vector and the system enters the specified Sx sleep state
7. System Wakes up
8. OSPM readies system for the return from the sleep state transition
1. Only buses that support hardware-defined enumeration methods are done automatically at run-time. This
would include ACPI-enumerated devices.
416 April, 2015 Version 6.0