Dynamic power management for embedded system
ÃƒËœ This dynamic power management refers to power management schemes implemented while programs are running.
ÃƒËœ This architecture is based on the capabilities of current and next-generation processors and their application requirements.
ÃƒËœ The overriding power management goal in portable system is to reduce system-wide energy consumption.
ÃƒËœ Dynamic power management is only concerned with voltage and frequency.
ÃƒËœ Dynamic power management architecture supports the ability of processors and external bus frequencies, in concerned with or even independent of the CPU frequency.
ÃƒËœ The low-level implementation of the dynamic power management architecture (DPM) is resident in the kernel of the operating system.
ÃƒËœ DPM is not a self-contained device driver.
ÃƒËœ Complete power management strategy is communicated to DPM in to ways: as an predefined set of policies and as an application/policy-set specific manager that manages them.
ÃƒËœ Policies specify the component and device-state transitions that ensure reliable operation in line with the power management strategy.
ÃƒËœ DPM policy managers are executable programs that activate policies by name.
ÃƒËœ Policy managers implement user defined and/or application-specific power management strategies. They can execute either as part of the kernel or in user space (or both) as required by the strategy.
ÃƒÂ¼ Operating point may be described different parameters such as core voltage, CPU bus frequencies and states of peripheral devices.
ÃƒÂ¼ Operating points for the IBM PowerPC 405LP specify a core voltage level, CPU and bus frequencies, memory timing parameters and other clocking related data.
ÃƒËœ OPERATING STATES
ÃƒÂ¼ In dynamic power management policy, operating state associated with an operating point specific to the requirements of that state.
ÃƒÂ¼ Operating state was the observation that includes the system-wide energy savings, it can be done by reducing CPU and bus frequency and core voltage while the system is in ideal state.
DEVICE CONSTRAINT MANAGER
ÃƒËœ Automatic selection of operating points as devices change states is a central feature of DPM.
ÃƒËœ Embedded systems may not have a BIOS or machine abstraction layer to insulate the operating system from low-level device and power management.
ÃƒËœ The most aggressive power management strategies will also require the system designer to carefully consider the influence of attached devices on the strategy.
Implementation and Effects Of task_specific Operating States
ÃƒËœ task-specific operating points,implemented by assigning different task operating states to different tasks.
ÃƒËœ The task state of a task is changed by the set_task_state () entry point, which may be exported to the user level as a system call.
Thus a system can be constructed where a single intelligent policy manager controlled the task states of critical programs for improved power/performance efficiency.