Ubuntu Wiki

ASPM PCIe Bug

As noted by Phoronix ASPM PCIe power saving has been problematic and a recent patch by Matthew Garrett has re-worked this to clear the ASPM state on all devices on a successful handoff of PCIe control to the OS.

We therefore are providing patched kernels carrying Matthew's fix for testing purposes only to see how well this works across a broad range of machines. Kernels can be found in:

• Ubuntu Oneiric 11.10 Kernels

• Ubuntu Precise 12.04 Kernels

For power measurement, we currently recommend using the older version of powertop 1.13 as this clearly displays the ACPI estimated power consumption. A .deb for this can be found [[https://launchpad.net/~colin-king/+archive/powermanagement|here]. We recommend running powertop as follows:

• Boot the machine, start powertop 1.13
• Wait until you get an ACPI estimated power consumption value.
• Gather 15 measurements (it is updated regularly).
• Discard the 5 results.
• Take average of the last 10 results.

Testing procedure:

• Ensure laptop is fully charged
• Unplug AC power
• Run powertop on an idle system and note power consumption
• Plug in AC power
• Install the new kernel containing the ASPM fix
• Ensure laptop is fully charged
• Unplug AC power
• Run powertop on an idle system and note power consumption
• Gather the BIOS version using: sudo dmidecode -t 0 | grep "Version:"
• Add results to the table below: