Open Source Summit + Embedded Linux Conference Europe 2020

Power Management is necessary for embedded devices because of the limited power capacity. Kernel provides DEVFREQ (Device Frequency) framework to optimize the power management for Non-CPU devices such as GPU, memory bus, storage and so on. The market requires high-quality image generated by GPU and data transfer via memory bus quickly and low latency for accessing the storage. In result, the power is more used than before. The power management for Non-CPU device is mandatory on embedded device. DEVFREQ provides the multiple governors for supporting DVFS and allows user to add their own governor instead of using default governors. But, DVFS feature is not enough to meet the performance demands. It supports PM_QOS interface to set the min/max requirements by user and collaborates with interconnect framework in order to guarantee the min/max bus bandwidth. Also, it is connected with thermal subsystem to protect overheat of device. Like this, DEVFREQ provides the power-management mechanism and the extensible flexibility to user. In this session, explain how to optimize the power management with DEVFREQ and how to develop DEVFREQ driver.