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SubjectRe: [Regression] PCI / PM: Simplify device wakeup settings code
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On 04/16/2018 11:58 AM, Rafael J. Wysocki wrote:
> On Mon, Apr 16, 2018 at 5:31 PM, Joseph Salisbury
> <joseph.salisbury@canonical.com> wrote:
>> On 04/13/2018 05:34 PM, Rafael J. Wysocki wrote:
>>> On Fri, Apr 13, 2018 at 7:56 PM, Joseph Salisbury
>>> <joseph.salisbury@canonical.com> wrote:
>>>> Hi Rafael,
>>>>
>>>> A kernel bug report was opened against Ubuntu [0]. After a kernel
>>>> bisect, it was found that reverting the following two commits resolved
>>>> this bug:
>>>>
>>>> 0ce3fcaff929 ("PCI / PM: Restore PME Enable after config space restoration")
>>>> 0847684cfc5f("PCI / PM: Simplify device wakeup settings code")
>>>>
>>>> This is a regression introduced in v4.13-rc1 and still exists in
>>>> mainline. The bug causes the battery to drain when the system is
>>>> powered down and unplugged, which does not happed prior to these two
>>>> commits.
>>> What system and what do you mean by "powered down"? How much time
>>> does it take for the battery to drain now?
>> By powered down, the bug reporter is saying physically powered off and
>> unplugged. The system is a HP laptop:
>>
>> dmi.chassis.vendor: HP
>> dmi.product.family: 103C_5335KV HP Notebook
>> dmi.product.name: HP Notebook
>> vendor_id : GenuineIntel
>> cpu family : 6
>>
>>
>>>> The bisect actually pointed to commit de3ef1e, but reverting
>>>> these two commits fixes the issue.
>>>>
>>>> I was hoping to get your feedback, since you are the patch author. Do
>>>> you think gathering any additional data will help diagnose this issue,
>>>> or would it be best to submit a revert request?
>>> First, reverting these is not an option or you will break systems
>>> relying on them now. 4.13 is three releases back at this point.
>>>
>>> Second, your issue appears to be related to the suspend/shutdown path
>>> whereas commit 0ce3fcaff929 is mostly about resume, so presumably the
>>> change in pci_enable_wake() causes the problem to happen. Can you try
>>> to revert this one alone and see if that helps?
>> A test kernel with commits 0ce3fcaff929 and de3ef1eb1cd0 reverted was
>> tested. However, the test kernel still exhibited the bug.
> So essentially the bisection result cannot be trusted.

We performed some more testing and confirmed just a revert of the
following commit resolves the bug:

0847684cfc5f0 ("PCI / PM: Simplify device wakeup settings code")

Can you think of any suggestions to help debug further?



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