a critical typo in the code managing the ASPM settings for PCI Express devices

[AceLan Kao]

[Impact]
The typo in the original code led to the PCI_EXP_LNKCTL register values being swapped between the parent PCI device and its child device.
It may lead to incorrect power state, device malfunction on system resume, or potential data loss or system stability issues.

[Fix]
Kaiheng submitted a patch to fix the issue and has been included in v6.9 mainline kernel.
f3d049b35b01 PCI/ASPM: Restore parent state to parent, child state to child

[Test]
There is no test cases for the issue now.

[Where problems may occur]
It fixes the typo and should not introduce any regression.

[Luis Alberto Pabón (copong)]

Thank you Acelan Kao. Will there be a kernel build for noble in -proposed?

[Luis Alberto Pabón (copong)]

I recompiled the 6.8.0-36 kernel with that patch and that solved the issue I have and described at https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2071604

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is awaiting verification that the linux/6.8.0-40.40 kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-noble-linux' to 'verification-done-noble-linux'. If the problem still exists, change the tag 'verification-needed-noble-linux' to 'verification-failed-noble-linux'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

[Luis Alberto Pabón (copong)]

Kernel 6.8.0-40.40 solves this problem.