Improvement And Implementation Of Power Management In Embedded Linux System

With wide adoption and rapid development of Embedded Linux systems,the requirements from users on lowering power consumption and increasing battery life on such systems are much higher than ever.Therefore,power management in Embedded Linux system is always a important part of device development on Embedded Linux.Currently,researches in this domain are mostly focused technologies on individual components of the system.Howerver,with continuing evolving of hardware,researches for cooperating among task scheduling,processor dynamic power management as well as related components under multi core and Heterogeneous Multi-Processing architecture are more important.We perform a thorough research and analysis on current Embedded Linux system power management architecture and technologies in this paper,unveil problems in current situation,implement improvements from CPU scheduling as well as device power management.Our work includes:1.Analyzed exisiting technologies in Embedded Linux system power management as well as problems in both CPU scheduling and device power management thoroughly.2.On CPU scheduling,starting from the isolation of scheduler and dynamic power management of processors and absent of cooperation problem,we proposed energy aware scheduler design.It is designed to lower the overall processor power consumption by corporating task scheduling and adjustment of voltages as well as frequencies of CPU cores.The design is based on improvement of current load tracking algorithm.It includes improvement on task placement,task balancing as well as co-working with CPUFreq subsystem.It lowers the overall processor power consumption by placing tasks on the CPU core or CPU cluster with the least power cost.3.On device power management,first we introduced the design principal of Linux Runtime PM framework as well as hardware power management feature in Atmel MXT1664 touch controller.We proposed a device dynamic power management design starting from solving the problem how to figure out when to put device to low power mode.We adopted an idle time prediction mechanism instead of fixed timeout to improve power management efficient and lower power consumption even further by reduce overhead from entering and exiting low power mode frequently.4.With testing on the Qualcomm MSM8996 and APQ8074 hardware platform,we verified improvement on CPU idle time and high CPU frequency time with the energy aware scheduler design.We also verified improvement on MXT1664 power consumption from the device dynamic power management design.In this paper,we firstly introduced background of this research and literature survey in Embedded Linux system power management.Secondly,raised problems in existing technologies.Then,we proposed our improvement design on both CPU scheduling and device dynamic power management with implementation in source code.At last,verified effectiveness of our design by test data on hardware platform.