Dynamic power management applies to embedded Linux, too

Weinberg, Bill; Mehaffey, John
September 2004
Portable Design;Sep2004, Vol. 10 Issue 9, p22
The article says that any dynamic power management (DPM) strategy begins with scaling the operating voltage and frequency of the one or more processor cores present in a portable device. In the DPM architecture for Linux, the DPM subsystem within the kernel maintains the system's power state and ties together the various power-managed elements of a DPM system. Relatively few if any other parts of the kernel need to interact with DPM directly. DPM is best thought of as a service provider to drivers, middleware and applications. End-user programs fall into one of three categories power management (PM)-aware, legacy applications in PM-aware "wrappers" and legacy applications with no power management. Power management aware applications can leverage the API available from a policy manager to establish their base constraints or force changes in power management policy to match their execution requirements. Modern embedded processors like OMAP and XScale can scale frequencies with latencies measured in a handful of microseconds and respond to changing voltages with a latency measured in tens of microseconds, all without interrupting system operations, allowing for much more aggressive and fine-grained policies.


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