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

[Bjorn Helgaas]

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.

Bjorn