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Device performance states (Px states) are power consumption and capability states within the active (D0) device power state. Performance states allow OSPM to make tradeoffs between performance and energy conservation. Device performance states have the greatest impact when the implementation is such that the states invoke different device efficiency levels as opposed to a linear scaling of performance and energy consumption. Since performance state transitions occur in the active device states, care must be taken to ensure that performance state transitions do not adversely impact the system. Device performance states, when necessary, are defined on a per device class basis (See Appendix A: Device Class Specifications for more information).
ACPI
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Device Performance States Proposal
_DPT
ACPI object to describe polling time in milliseconds.
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This method is optional if there are other ways for OSPM to derive delivered performance. For example, if ClockInput resources are provided for the device in _CRS method then OSPM can utilize that to know the delivered performance.
Example with I.MX8MP DDR Controller
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