Linux 5.19 heavy on Intel power management and thermal improvements

Power management, ACPI, and thermal control updates are ready for Linux 5.19. This cycle there is a lot of PM/thermal work as usual on the Arm side while Intel also continues with a lot of changes from new hardware support to improved laptop overheat handling for S0ix management .

As always, he’s working on improving Linux power management and thermal management of hardware, from smartphones to high-performance servers. Power management changes for Linux 5.19 include:

– Intel Run-Time Average Power Limiting (RAPL) driver adds support for Raptor Lake and Alder Lake N processors.

– Alder Lake support in Intel Idle driver.

– Intel P-Strate driver now correctly handles frequency invariance handling when turbo mode is disabled using the /sys/devices/system/cpu/intel_pstate/no_turbo sysfs interface. When the user chooses to disable turbo mode using this runtime interface, frequency invariance handling would be removed.

– Sapphire Rapids Out-of-Band (OOB) mode support for Intel P-State driver.

– A fix led by Linaro to avoid unnecessary frequency updates when the frequency reported by the hardware is slightly different than the one indicated by the frequency chart – eg 499 vs. 500 MHz. The patch in its current form allows up to 1 MHz deviation without causing frequency updates.

– ACPI table replacement is now preserved during the hibernation process.

– Support for CPU-based scaling has been added to the devfreq passive governor.

– The energy model code has been extended to allow for artificial models where power values ​​may not be on a uniform scale with other devices providing power information. This is an Arm-led change to the artificial energy model.

More details on power management changes via this pull request.

During this time the ACPI updates include additions such as support for Microsoft Windows 11 _OSI string, addition of ARM performance monitoring unit table in ACPICA code, better handling of PCI devices that are in D3cold state when from system initialization, support for high frequency impedance notification to the DPTF driver, and other additions. The ACPI change around D3cold devices during system initialization will now ensure that PCI devices are initially powered up with their children to ensure correct device enumeration.

On similar topics, the thermal control updates have been merged. This pull includes the new thermal library and temperature capture tool in the kernel source tree. This pull also improves handling of overheat conditions during idle suspend in the Intel PCH thermal driver and a variety of other fixes and improvements.

Improved handling of Intel PCH overheating during sleep is the change covered in detail earlier this month in Intel has a fix for hot Linux laptops draining the battery while trying to sleep.

Alan A. Seibert