ACPI, Power Management Get Big Linux 3.13 Updates
Written by Michael Larabel in Linux Kernel on 8 November 2013 at 11:27 AM EST. 31 Comments
The Linux 3.13 kernel merge window has become even more exciting even though it's not even officially open yet. Besides many to-be-merged changes talked about on Phoronix already, the ACPI and power management pull is particularly exciting for ARM and Intel Linux users.

With Linux 3.13, ARM's big.LITTLE CPUFREQ driver now supports in-kernel switching between the "big" and "little" cores as part of its performance-scaling. The big.LITTLE implementations we have seen so far are commonly four Cortex-A15 cores making up the "big" performant portion and than four low-power low-performance Cortex-A7 cores when the system is not busy. The CPUFREQ driver for Linux 3.13 now supports in-kernel switching between these different ocres as part of its performance scaling.

The Intel P-State driver in Linux 3.13 will also support Atom "Bay Trail" SoCs as another exciting change going beyond its Sandy Bridge, Ivy Bridge, and Haswell CPU support.

The other big stuff in the Linux 3.13 ACPI and power management pull request is the introduction of the Linux power-capping framework and RAPL driver for run-time average power-limiting. Power-capping paired with the Intel RAPL driver allows systems to limit the power draw of various system components, assuming the hardware supports such capabilities.

Some other good stuff with this update is CPUfreq for the Apple iMac G5, CPUfreq for Calxeda's "Midway" ECX-2000 platform, and many other fixes and updates.

Last but not least the ACPICA code was updated to match upstream 20130927 with ACPI power management now being supported for the I2C and SPI buses.

While Linus is expected to open the Linux 3.13 kernel merge window over the weekend, this ACPI/PM pull request can be found already as of this morning on the kernel mailing list.

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Michael Larabel is the principal author of and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and automated benchmarking software. He can be followed via Twitter or contacted via

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