POWER MANAGEMENT IN WINDOWS-CE (HAND-HELD DEVICES)

1. POWER MANAGEMENT IN WINDOWS-CE(HAND-HELD DEVICES) By: Ankur Agarwal

2. MOTIVATION • Complex Application on Portable System • Images • Gaming • Video Clips • Reduction in Weight and Size • Catastrophic Data Loss

3. POWER MANAGEMENT AT DIFFERENT LEVELS • Transistor Level • Architecture Level • Application Level • System Level (Operating System) ABSTRACTION

4. SYSTEM LEVEL POWER MANAGEMENT • Power Manager is a Part of System Level Power Management. It manages • Applications • Devices • Processor • It collects the information from the various interfaces • Based on the information it puts the whole system into lowest possible power state suitable for a particular application.

6. DEVICE LEVEL POWER MANAGER PM POLICY MANAGER APPLICATION LEVEL POWER MANAGER POWER MANAGEMENT ARCHITECTURE DEVICE DRIVERS APPLICATION SUBSYSTEM BATTERY

7. POWER MANAGEMENT ARCHITECTURE • Both Application and Device drivers in the system are dependent on the services of the Power Manager. • The Power Manager provides Applications and Drivers with the necessary means to comprehend system-level changes and adapt their power states accordingly. • Windows CE .NET has a comprehensive set of Power Management APIs for both device drivers and applications within a Power Manager component.

8. POWER MANAGEMENT SOFTWARE ARCHITECTURE • Handles system-wide Power Management policy. • Manages the system, Device & processor states to minimize the power consumption. • Provides a set of services for applications in the system to get notifications on the system-level state changes. • Provides the mean of applications to request specific levels of availability and performance from the system and in certain cases, from the device that the application is dependent on.

9. POWER MANAGEMENT SOFTWARE ARCHITECTURE • Provides a set of services for the device drivers in the system to get notifications on the system level state changes & respond to it. • Provides a means for the drivers to communicate to their power state. • Monitors critical resources in the system. • Monitors processor utilization and ensures that the processor is operating at the lowest possible power state.

10. POWER MANAGER DEVICE NOTIFIER DEVICE DRIVER OR PROXY +REQUESTPOWERNOTIFICATION ( ) +STOPPOWERNOTIFICATION ( ) +UPDATEDEVICEPOWERSTATE ( ) +GETDEVICEPOWERCAPABILITIES ( ) +GETDEVICEPOWERSTATE ( ) +SETDEVICEPOWERSTATE ( ) DEVICE LEVEL POWER MANAGEMENT PM NOTIFICATION INTERFACE DRIVER PM INTERFACE CLASS DIAGRAM

11. Provides the means for Power Manager to notify drivers about various system-level power state changes. E.g. : Plugging a new application POWER MANAGER DEVICE NOTIFIER +REQUESTPOWERNOTIFICATION ( ) +STOPPOWERNOTIFICATION ( ) +UPDATEDEVICEPOWERSTATE ( ) PM NOTIFICATION INTERFACE

12. Provides a means for the Power Manager to get and set specific capabilities at the device driver level. Device drivers must support the Power Management States DEVICE DRIVER OR PROXY +GET DEVICE POWER CAPABILITIES ( ) +GET DEVICE POWER STATE ( ) + SET DEVICE POWER STATE ( ) DEVICE CONTROL POWER MANAGER

13. DEVICE DRIVER PM DEVICE NOTIFIER PM POLICY MANAGER BATTERY DRIVER RequestPowerNotification ( ) Query System State To Standby ( ) Get Batt Level ( ) Accept System State Modification( ) Current Batt Level ( ) Low Batt Event ( ) Notify System State to LowBatt ( ) Notify System State to Standby ( ) SystemOn Event ( ) Notify System State to On ( ) DEVICE DRIVER INTRACTION WITH POWER MANAGER SEQUENCE DIAGRAM

14. DEVICE DRIVER INTRACTION WITH POWER MANAGER • POLICY MANAGER • Monitors the Power State Change request. • Monitors the Battery charge life (Battery Driver). • Notifies when the battery is low. • In case of critical battery, it shuts down the whole system.

15. DEVICE DRIVER INTRACTION WITH POWER MANAGER • Device drivers register themselves to receive notification from the PM Device Notifier. • On detecting idle-state for the defined threshold, the Policy Manager sends a Query System State Mod to Standby event (in this example) to the device driver (through the Device Notifier) to check if the device drivers are ready to change the system state to Standby. • The PM Device Notifier sends a Query System State Mod to all the device drivers registered with it. • When all device drivers have accepted the Query, the PM Policy Manager puts the system into the new power state.

16. DEVICE DRIVER PM IN WIN CE.NET • Handles Power requests sent by power manager. • Inform power manager of the power capabilities of the device driver and the supported power modes. • Power-up the device on system startup.. • Power down the device when idle. • Changes the device power states as per requirement.

17. APPLICATION NOTIFICATION MANAGER SYSTEM LEVEL APPLICATION POWER MANAGER +REQUESTPOWERNOTIFICATION ( ) +STOPPOWERNOTIFICATION ( ) +GETSYSTEMPOWERSTATE ( ) +SETSYSTEMSTATETOON ( ) +SETSYSTEMSTATETOON ( ) APPLICATION LEVEL POWER MANAGEMENT PM NOTIFICATION INTERFACE SYSTEM LEVEL PM INTERFACE CLASS DIAGRAM

18. DEVICE CONTROL POWER MANAGER +GETDEVICEPOWERSTATE ( ) +SETDEVICEPOWERREQUIREMENT ( ) +SETDEVICEPOWERREQUIREMENT ( ) APPLICATION LEVEL POWER MANAGEMENT DRIVER LEVEL PM INTERFACE CLASS DIAGRAM

19. APPLICATION NOTIFICATION MANAGER +REQUESTPOWERNOTIFICATION ( ) +STOPPOWERNOTIFICATION ( ) APPLICATION NOTIFICATION MANAGER • The Application Notification Manager provides the means for the Power Manager to notify applications about various system-level Power state changes required. PM NOTIFICATION INTERFACE

20. SYSTEM LEVEL APPLICATION POWER MANAGER +GETSYSTEMPOWERSTATE ( ) +SETSYSTEMSTATETOON ( ) +SETSYSTEMSTATETOON ( ) SYSTEM LEVEL APPLICATIONPOWER MANAGER • The System-level Application PM is used to get and set system-level power states. It is also the means to get the current Battery state. SYSTEM LEVEL PM INTERFACE

21. DEVICE CONTROL POWER MANAGER • The Device Control PM provides a means for applications to set specific guidelines for devices that Applications can request to set the system power level. Applications can request the Power Manager to alter a device's power state transition. DRIVER LEVEL PM INTERFACE DEVICE CONTROL POWER MANAGER +GETDEVICEPOWERSTATE ( ) +SETDEVICEPOWERREQUIREMENT ( ) +SETDEVICEPOWERREQUIREMENT ( )

22. APPLICATION INTRACTION WITH ANM

23. APPLICATION INTRACTION WITH ANM • POLICY MANAGER • Monitors the Power State Change request. • Monitors the Battery charge life (Battery Driver). • Notifies when the battery is low. • In case of critical battery, it shuts down the whole system.

24. APPLICATION LEVEL POWER MANAGER SERVICES • The Applications register themselves to receive notification from the App Notification Manager. • On detecting idle-state for the defined threshold, the Policy Manager sends a Query Standby event to the Application. • The Application Manager sends a Query System State Mod to all the applications registered with it. • When all applications have accepted the Query, the App Notification Manager notifies the PM. • Policy Manager which then puts the system into Standby state.

26. APPLICATION LEVEL POWER MANAGER SERVICES • Set Device Power Requirement • Release Device Power Requirement • Acknowledge • Set Device Power State • Get Device Power State • Device Power State