Power Management

CPUFREQ_DT works as of 66e47a83

root@usbarmory-hacking:~# cpufreq-info 
cpufrequtils 008: cpufreq-info (C) Dominik Brodowski 2004-2009
Report errors and bugs to [email protected], please.
analyzing CPU 0:
  driver: cpufreq-dt
  CPUs which run at the same hardware frequency: 0
  CPUs which need to have their frequency coordinated by software: 0
  maximum transition latency: 61.0 us.
  hardware limits: 167 MHz - 1000 MHz
  available frequency steps: 167 MHz, 400 MHz, 800 MHz, 1000 MHz
  available cpufreq governors: userspace, conservative, powersave, ondemand, performance
  current policy: frequency should be within 167 MHz and 1000 MHz.
                  The governor "ondemand" may decide which speed to use
                  within this range.
  current CPU frequency is 167 MHz (asserted by call to hardware).
  cpufreq stats: 167 MHz:53.33%, 400 MHz:11.50%, 800 MHz:7.08%, 1000 MHz:28.08%  (36)

Overclocking and underclocking from the nominal 800 MHz speed of the USB Armory works.

• hibernate/resume to disk?
  • https://wiki.archlinux.org/index.php/Suspend_and_hibernate
  • http://elinux.org/ARM_Hibernation
  • http://elinux.org/Suspend_To_Disk_For_ARM
  • http://www.spinics.net/lists/arm-kernel/msg125975.html
  • https://www.kernel.org/doc/Documentation/power/basic-pm-debugging.txt
  • https://wiki.debian.org/Suspend
  • https://wiki.ubuntu.com/DebuggingKernelHibernate

Short version: hibernate and resume work, but the MMC controller is initialized after the power management framework. With patched init scripts it is possible to resume fairly early in the boot process. Still investigating how to make MMC initialize sooner.