New Power Management Phases For Linux 3.4 Kernel

Just one day after the Linux 3.3 kernel was released, the power management pull request for the Linux 3.4 kernel has already been submitted.

Rafael J. Wysocki submitted the email pull request with the power management changes for the 3.4 kernel. Key items include the introduction of early/late suspend/hibernation device call-backs, generic PM domains extensions and fixes, devfreq updates, device PM QoS updates, concurrency problem fixes, and system suspend and hibernation fixes.

There isn't anything too exciting about this pull request, but of the 3.4 power management work, the most interesting item is arguably the "early/late suspend/hibernation device call-backs." This work comes down to "late suspend" and "early resume" phases for Linux device power management. These are optional call-backs for drivers to utilize after run-time power management is disabled and with device interrupts enabled. More details about this particular work can be found from the original mailing list thread when this work was initially published last December.

While not part of the main Linux power management pull, also announced to the kernel mailing list today was the AVS class of drivers. From the mailing list announcement, "AVS is a power management technique which controls the operating voltage of a device in order to optimize (i.e. reduce) its power consumption. The voltage is adapted depending on static factors (chip manufacturing process) and dynamic factors (temperature depending performance). AVS is also called SmartReflex on OMAP devices."

Previously there's been a OMAP2 SmartReflex power driver living elsewhere, but with this patch-set it ends up creating an AVS framework within the Linux kernel. At this time, only the Texas Instruments OMAP2/OMAP3+ hardware with the SmartRefle code is taking advantage of AVS in the Linux kernel.