Powertop reports “Bad” “Runtime PM for PCI Device”

Question

I've noticed that powertop utility reports "Bad" "Runtime PM for PCI Device" for several devices. Seems that powertop can fix the issue but it won't tell what exactly it does to fix it. What should I do to fix that "Runtime PM..." issue?

Answer 1

This CrunchBang Linux forum thread helped me to solve this.

You enable PM for each of your PCI devices this way :

echo auto > /sys/bus/pci/devices/*/power/control 

The forum thread shows a nice powersaving script btw.

UPDATE: was cat, but echo is correct

Answer 2

Create a file called /etc/udev/rules.d/10-runtime-pm.rules with the following content:

SUBSYSTEM!="pci", GOTO="power_runtime_rules_end"
ACTION!="add", GOTO="power_runtime_rules_end"

KERNEL=="????:??:??.?"
PROGRAM="/bin/sleep 0.1"

ATTR{power/control}=="*", ATTR{power/control}="auto"

LABEL="power_runtime_rules_end"

After a reboot runtime PM should be enabled for all devices that support it. It is also enables it for all hotplugged devices.