ACPI and Power Management Updates Merged into Linux 4.19

ACPI and power management updates are never ending work, and today Intel’s Rafael Wysocki has submitted some note worthy updates for the Linux 4.19 kernel, which were merged thereafter by Linus Torvalds.

For starters, this adds a new framework for CPU idle time injection, which will be used by all of the idle injection code in the kernel in the future. It also fixes a few issues and adds a number of fairly small extensions in a few places.

Some of the more specific changes from the mailing list:

  • Add a new framework for CPU idle time injection (Daniel Lezcano).
  • Add AVS support to the armada-37xx cpufreq driver (Gregory CLEMENT).
  • Add support for current CPU frequency reporting to the ACPI CPPC cpufreq driver (George Cherian).
  • Rework the cooling device registration in the imx6q/thermal driver (Bastian Stender).
  • Make the pcc-cpufreq driver refuse to work with dynamic scaling governors on systems with many CPUs to avoid scalability issues with it (Rafael Wysocki).
  • Fix the intel_pstate driver to report different maximum CPU frequencies on systems where they really are different and to ignore the turbo active ratio if hardware-managend P-states (HWP) are in use; make it use the match_string() helper (Xie Yisheng, Srinivas Pandruvada).
  • Fix a minor deferred probe issue in the qcom-kryo cpufreq driver (Niklas Cassel).
  • Add a tracepoint for the tracking of frequency limits changes (from Andriod) to the cpufreq core (Ruchi Kandoi).
  • Fix a circular lock dependency between CPU hotplug and sysfs locking in the cpufreq core reported by lockdep (Waiman Long).
  • Avoid excessive error reports on driver registration failures in the ARM cpuidle driver (Sudeep Holla).
  • Add a new device links flag to the driver core to make links go away automatically on supplier driver removal (Vivek Gautam).
  • Eliminate potential race condition between system-wide power management transitions and system shutdown (Pingfan Liu).
  • Add a quirk to save NVS memory on system suspend for the ASUS 1025C laptop (Willy Tarreau).
  • Make more systems use suspend-to-idle (instead of ACPI S3) by default (Tristian Celestin).
  • Get rid of stack VLA usage in the low-level hibernation code on 64-bit x86 (Kees Cook).
  • Fix error handling in the hibernation core and mark an expected fall-through switch in it (Chengguang Xu, Gustavo Silva).
  • Extend the generic power domains (genpd) framework to support attaching a device to a power domain by name (Ulf Hansson).
  • Fix device reference counting and user limits initialization in the devfreq core (Arvind Yadav, Matthias Kaehlcke).
  • Fix a few issues in the rk3399_dmc devfreq driver and improve its documentation (Enric Balletboi Serra, Lin Huang, Nick Milner).
  • Drop a redundant error message from the exynos-ppmu devfreq driver (Markus Elfring).

Kamil Anwar


A former British Computer Society Member with over 9 years of experience Configuring, Deploying and Managing Switches, Firewalls and Domain Controllers also an old-school still active on FreeNode.