Linux-next commit 7f92c4f7d92a7558ed7eb29fa59e1c98402dc3c2 addresses
the PCIe ASPM issues that a lot of folk are suffering from. This fix
is a re-working of the PCIe ASPM code which is now more aligned to the
Windows behaviour. Currently we clear ASPM states on all the
devices if the BIOS indicates that APSM is not supported, this fix
won't touch the PCIe features unless full control is granted via the
_OSC control method.
We believe that this fix will land in Linux 3.3, so I'm requesting
this is incorporated for Precise as it addresses a long standing
power management issue.
Lenovo X220i, saves ~1W (measured with Fluke digital multimeter),
soak tested for 5 minutes on idle system.
Garrett has observed > 5W saving on a ThinkPad X220.
* Significant power savings (>2 Watts) on: Dell XPS 1330M,
Dell Inspiron N4010, Dell Studio 1558, HP Compaq nw8240,
HP Mini 210, ThinkPad T410, ThinkPad T420, Thinkpad T420s,
Thinkpad T510, Thinkpad X201, Thinkpad X220, Thinkpad X220.
* 13+ machines seeing < 2 Watts savings
* Rest seeing little or some minor loss, but within the expected
margin of error on battery power measurements.
* 43 machines were tested.
Matthew Garrett (1):
pci: Rework ASPM disable code