The pull requests landing the power management subsystem updates for Linux 6.19 along with the ACPI and thermal control code have landed. There is new hardware support, Microsoft ACPI Fan Extensions support, and other new features for Linux power management in this new kernel.
The ACPI pull request adds Microsoft fan extensions to the Linux ACPI fan driver. Plus runtime power management improvements to the ACPI Time and Alarm Driver (TAD) and various small fixes throughout.
The Microsoft ACPI Fan Extensions were previously talked about on Phoronix back in October with Linux Patches Posted For Microsoft’s ACPI Fan Extensions. By supporting these Microsoft extensions for the OS to set fan speed trip points, it should help improve support for some HP systems and likely other OEMs too for obtaining fan information correctly under Linux.
There was also the power management updates for Linux 6.19 to land as well. The Intel P-State and Runtime Average Power Limiting (RAPL) drivers are ready for the Panther Lake, Wildcat Lake, Nova Lake, and Diamond Rapids processors.
There is also a new power management QoS CPU latency limit for suspend-to-idle, netlink support for the energy model management, support for terminating systemd suspend via a wakeup event during the sync of file-systems, configurable number of hibernation compression threads, and other run-time power management improvements.
The work to make the number of system hibernation threads for compression/decompression configurable is interesting for better scalability with faster hibernation/resume. The default number of threads to use is three but increasing it to 5~6 can yield around a 12% latency improvement for resume time after hibernation. This can be set using the new “cmp_threads=” kernel parameter or via the /sys/power/hibernate_compression_threads sysfs file.
Lastly are the thermal control updates to mention in this article. There is now Nova Lake processor thermal driver support for the int340x driver, DLVR support for Nova Lake, and Nova Lake wired up to the ACPI DPTF code. The thermal pull also adds Qualcomm Kaanapali temperature sensor support for the Snapdragon X2 Elite.
