ASPM Kernel Power Fix Won't Land Until Linux 3.3
For those still wondering about the patches that appeared last month to mimic the power management behavior of Windows within the Linux kernel as a proper fix to the well known ASPM Linux kernel power regression, here's an update on the matter.
- All indications are that Matthew Garrett's patches from November have in fact addressed the Active State Power Management (ASPM) issue within the Linux kernel whereby the PCI Express feature is now being enabled on hardware where it actually works while at the same time it's not being flipped on for faulty hardware. In cases where PCI-E ASPM is flipped on but not properly supported by the hardware/firmware, stability issues and other problems are known to occur, but I haven't heard of any problems with this new ASPM logic incorrectly toggling the support on bad systems.
- The ASPM patches aren't being merged in the mainline tree until the Linux 3.3 kernel. This is since the work landed past the Linux 3.2 kernel merge window, among other factors. Right now the work is living in the "linux-next" tree.
- The "pci: Rework ASPM disable code" patch may end up appearing in the stable Linux kernel trees (for those that are still maintained past the Linux 2.6.38 kernel where the regression was introduced), but not before greater testing occurs. This would likely be at some point after the patch is merged and tested in Linux 3.3.
- For Ubuntu Linux users wishing to try out a pre-built kernel with the patch applied, there's details on this Ubuntu Wiki page along with an area where some users are sharing their results. While Ubuntu 12.04 LTS will be shipping with the Linux 3.2 kernel, regardless of when the main patch ends up landing in the stable series, Canonical will likely end up patching it for their "Precise Pangolin" kernel.
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