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

[Bjorn Helgaas]

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.

Probably a dumb question, but would it make sense to restore the
device_may_wakeup() check in pci_enable_wake(), e.g.,

diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index e597655a5643..9fa64c175f92 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1932,6 +1932,9 @@ int pci_enable_wake(struct pci_dev *dev, pci_power_t state, bool enable)
 {
 	int ret = 0;
 
+	if (enable && !device_may_wakeup(&dev->dev))
+		return -EINVAL;
+
 	/*
 	 * Bridges can only signal wakeup on behalf of subordinate devices,
 	 * but that is set up elsewhere, so skip them.