Re: [Regression] PCI / PM: Simplify device wakeup settings code

[Joseph Salisbury <joseph.salisbury@canonical.com>]

On 05/02/2018 06:41 AM, Rafael J. Wysocki wrote:
> On Tue, May 1, 2018 at 9:55 PM, Bjorn Helgaas <helgaas@kernel.org> wrote:
>> On Tue, May 01, 2018 at 10:34:29AM +0200, Rafael J. Wysocki wrote:
>>> On Mon, Apr 30, 2018 at 4:22 PM, Joseph Salisbury
>>> <joseph.salisbury@canonical.com> wrote:
>>>> 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")
>>> Thanks for confirming this!
>>>
>>>> Can you think of any suggestions to help debug further?
>>> The root cause of the regression is likely the change in
>>> pci_enable_wake() removing the device_may_wakeup() check from it.
>>>
>>> Probably, one of the drivers in the platform calls pci_enable_wake()
>>> directly from its ->shutdown() callback and that causes the device to
>>> be set up for system wakeup which in turn causes the power draw while
>>> the system is off to increase.
>>>
>>> I would look at the PCI drivers used on that platform to find which of
>>> them call pci_enable_wake() directly from ->shutdown() and I would
>>> make these calls conditional on device_may_wakeup().
>> I took a quick look with
>>
>>   git grep -E "pci_enable_wake\(.*[^0]\);|device_may_wakeup"
>>
>> and didn't notice any pci_enable_wake() callers that called
>> device_may_wakeup() first.
> I've just look at a bunch of network drivers doing that.
>
> It looks like I may need to restore __pci_enable_wake() with an extra
> "runtime" argument for internal use.
>
> Joseph, can you ask the reporter to test the Bjorn's patch, please?

Yes, I'll get him a test kernel and respond with the results.