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[Pali <pali.rohar@xxxxxxxxx>]

I tested 3.13.0.51.44 version of linux-image-generic-lts-trusty package
on Ubuntu Precise 12.04.5 (which contains trusty kernel backports).

And looks like it working fine. See log:

$ lspci -nn | grep 00:1c.7
00:1c.7 PCI bridge [0604]: Intel Corporation 8 Series/C220 Series Chipset Family PCI Express Root Port #8 [8086:8c1e] (rev d4)

$ sudo lspci -s 00:1c.7 -v -v | grep -i aspm
                LnkCap: Port #8, Speed 5GT/s, Width x1, ASPM L0s L1, Latency L0 <1us, L1 <16us
                LnkCtl: ASPM Disabled; RCB 64 bytes Disabled- Retrain- CommClk-

$ cat /sys/bus/pci/devices/0000:00:1c.7/power/link_state
0

$ echo 1 | sudo tee /sys/bus/pci/devices/0000:00:1c.7/power/link_state
1

$ sudo lspci -s 00:1c.7 -v -v | grep -i aspm
                LnkCap: Port #8, Speed 5GT/s, Width x1, ASPM L0s L1, Latency L0 <1us, L1 <16us
                LnkCtl: ASPM L0s Enabled; RCB 64 bytes Disabled- Retrain- CommClk-

$ echo 2 | sudo tee /sys/bus/pci/devices/0000:00:1c.7/power/link_state
2

$ sudo lspci -s 00:1c.7 -v -v | grep -i aspm
                LnkCap: Port #8, Speed 5GT/s, Width x1, ASPM L0s L1, Latency L0 <1us, L1 <16us
                LnkCtl: ASPM L1 Enabled; RCB 64 bytes Disabled- Retrain- CommClk-

$ echo 3 | sudo tee /sys/bus/pci/devices/0000:00:1c.7/power/link_state
3

$ sudo lspci -s 00:1c.7 -v -v | grep -i aspm
                LnkCap: Port #8, Speed 5GT/s, Width x1, ASPM L0s L1, Latency L0 <1us, L1 <16us
                LnkCtl: ASPM L0s L1 Enabled; RCB 64 bytes Disabled- Retrain- CommClk-

$ echo 0 | sudo tee /sys/bus/pci/devices/0000:00:1c.7/power/link_state
0

$ sudo lspci -s 00:1c.7 -v -v | grep -i aspm
                LnkCap: Port #8, Speed 5GT/s, Width x1, ASPM L0s L1, Latency L0 <1us, L1 <16us
                LnkCtl: ASPM Disabled; RCB 64 bytes Disabled- Retrain- CommClk-


 tag verification-done-trusty
 tag -verification-needed-trusty

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https://bugs.launchpad.net/bugs/1398544

Title:
  Please enable CONFIG_PCIEASPM_DEBUG

Status in linux package in Ubuntu:
  Fix Released
Status in linux source package in Trusty:
  Fix Committed
Status in linux source package in Utopic:
  Fix Committed
Status in linux source package in Vivid:
  Fix Released

Bug description:
  [Impact]
  CONFIG_PCIEASPM_DEBUG (which is currently disabled for Ubuntu kernels) can be used to enable/disable ASPM settings per PCIE device. CONFIG_PCIEASPM (which is enabled for Ubuntu kernels) allows only to set global ASPM policy. BIOSes on more machines are buggy and lot of times do not configure ASPM for PCIE device property. CONFIG_PCIEASPM_DEBUG option allows users or testers to hotfix potential bugs in BIOS... That config option only add new sysfs files so it should not break anything else in kernel.

  [Test Case]
  Try to use PCIe ASPM sysfs debug interface.

  [Fix]
  Enable CONFIG_PCIEASPM_DEBUG
  vivid discussion: https://lists.ubuntu.com/archives/kernel-team/2014-December/051914.html

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