Open Source Summit Europe 2024

DeviceTree (DT) based systems usually lack a platform or firmware based device power management framework. Device drivers are left to figure out if a device is already powered on at probe and duplicate power management logic to manage system resources such as clks or interconnects. This is unlike ACPI based systems where the firmware provides standardized device power states to power on or off a device and mostly hides system resources behind a firmware interface. This session will make the case for implementing an ACPI-like power management framework in the Linux kernel via pmdomains registered by a System-on-Chip (SoC) driver. First we'll discuss the problem and previously attempted or ongoing solutions. Then we'll cover a case study implementing an SoC power management driver. Attendees will leave with a greater understanding of SoC power management techniques and the problems kernel developers face in supporting such hardware upstream along with a possible solution to implement this design elsewhere.