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

[Rafael J. Wysocki]

On Thu, May 3, 2018 at 9:11 PM, Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote:
> On Thu, May 03, 2018 at 02:29:02PM -0400, Joseph Salisbury wrote:
>> On 05/02/2018 06:41 AM, Rafael J. Wysocki wrote:
>> > On Tue, May 1, 2018 at 9:55 PM, Bjorn Helgaas <helgaas@xxxxxxxxxx> 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@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx> 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@xxxxxxxxxxxxx> 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?
>>
>> The bug reporter has testing Bjorn's patch.  It did in fact resolve the
>> bug.  Thanks for the quick help, Rafael and Bjorn!
>
> Just as a word of caution, I think Rafael said my patch was not the
> right fix because it would break something else.  So I would wait for
> a better patch from Rafael before actually resolving this issue.

I'll do my best to provide one in the next couple of days.