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A Comment On The Linux 2.6.38 Power Regression

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  • #16
    Until drivers are updated...

    You can do things to help:
    - test your system with ASPM forced on (see previous articles on that)
    - test each device to make sure it operates properly after given time to transition into different ASPM states

    Assuming things work well for you, ping the appropriate driver maintainers for the devices in your system indicating that ASPM can safely be enabled for your devices (ideally with patches attached; see the e1000e driver for examples of how a driver can configure ASPM directly).

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    • #17
      Originally posted by jbarnes View Post
      You can do things to help:
      - test each device to make sure it operates properly after given time to transition into different ASPM states
      How do we know when a transition occurs? Also, I assume the "Unable to assume _OSC PCIe control. Disabling ASPM" warning is misleading and can be ignored?

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      • #18
        Originally posted by RealNC View Post
        How do we know when a transition occurs? Also, I assume the "Unable to assume _OSC PCIe control. Disabling ASPM" warning is misleading and can be ignored?
        Yes, if you set the force option, you can ignore this message.

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        • #19
          Originally posted by jbarnes View Post
          Yes, if you set the force option, you can ignore this message.
          I asked because this message does not appear if I don't set the force option. So most users will use the force option, and then (and *only* then) they will be told "Unable to assume _OSC PCIe control. Disabling ASPM". As you can imagine, this is extremely confusing

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          • #20
            Originally posted by jbarnes View Post
            Yes, if you set the force option, you can ignore this message.
            Oh and for testing you'll need to look at the output of lspci to make sure your device supports ASPM and that it's enabled. Hardware will transition into L0S or L1 automatically after very short periods of time; to really check if things are working you'd need to measure power differences. But if the device is broken and hangs you'll probably notice in that case.

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            • #21
              Windows 7 ASPM

              Let me just point out, that Windows does indeed blacklist drivers that don't use ASPM correctly. Probably to prevent crashes.

              If you run
              Code:
              powercfg -energy
              , you get a report about the power usage of your system.

              On my PC, USB suspending and ASPM doesn't work:

              Code:
              Platform Power Management Capabilities:PCI Express Active-State Power Management (ASPM) Disabled
              PCI Express Active-State Power Management (ASPM) has been disabled due to a known incompatibility with the hardware in this computer.
              I think in my case, it's the ATI Catalyst drivers that cause ASPM to not work. I guess it could also be bios related, but my motherboard is otherwise high quality.

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              • #22
                An informative message from mjg59:
                http://lwn.net/Articles/449648/

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