More than 10 yrs ago Runtime PM was disabled per default by bb910a7040
("PCI/PM Runtime: Make runtime PM of PCI devices inactive by default").
Reason given: "avoid breakage on systems where ACPI-based wake-up is
known to fail for some devices"
Unfortunately the commit message doesn't mention any affected devices
or systems.
With Runtime PM disabled e.g. the PHY on network devices may remain
powered up even with no cable plugged in, affecting battery lifetime
on mobile devices. Currently we have to rely on the respective distro
or user to enable Runtime PM via sysfs (echo auto > power/control).
Some devices work around this restriction by calling pm_runtime_allow
in their probe routine, even though that's not recommended by
https://www.kernel.org/doc/Documentation/power/pci.txt
Disabling Runtime PM per default seems to be a big hammer, a quirk
for affected devices / systems may had been better. And we still
have the option to disable Runtime PM for selected devices via sysfs.
So, to cut a long story short: Wouldn't it be time to remove this
restriction?
