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

[Rafael J. Wysocki]

On Thursday, May 3, 2018 11:29:18 PM CEST Rafael J. Wysocki wrote:
> 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.

Something like the appended one (compiled-only at this point).

Joseph, this should be functionally equivalent to the Bjorn's patch except
for the runtime PM part which is irrelevant for the issue in question, but
please ask the reported to test this one too.

If it is confirmed to work, I'll repost it with a proper changelog.

---
 drivers/pci/pci.c |   31 ++++++++++++++++++++++++-------
 1 file changed, 24 insertions(+), 7 deletions(-)

Index: linux-pm/drivers/pci/pci.c
===================================================================
--- linux-pm.orig/drivers/pci/pci.c
+++ linux-pm/drivers/pci/pci.c
@@ -1910,7 +1910,7 @@ void pci_pme_active(struct pci_dev *dev,
 EXPORT_SYMBOL(pci_pme_active);
 
 /**
- * pci_enable_wake - enable PCI device as wakeup event source
+ * __pci_enable_wake - enable PCI device as wakeup event source
  * @dev: PCI device affected
  * @state: PCI state from which device will issue wakeup events
  * @enable: True to enable event generation; false to disable
@@ -1928,7 +1928,7 @@ EXPORT_SYMBOL(pci_pme_active);
  * Error code depending on the platform is returned if both the platform and
  * the native mechanism fail to enable the generation of wake-up events
  */
-int pci_enable_wake(struct pci_dev *dev, pci_power_t state, bool enable)
+static int __pci_enable_wake(struct pci_dev *dev, pci_power_t state, bool enable)
 {
 	int ret = 0;
 
@@ -1969,6 +1969,23 @@ int pci_enable_wake(struct pci_dev *dev,
 
 	return ret;
 }
+
+/**
+ * pci_enable_wake - enable PCI device as wakeup event source
+ * @pci_dev: Target device
+ * @state: PCI state from which device will issue wakeup events
+ * @enable: Whether or not to enable event generation
+ *
+ * If @enable is set and device_may_wakeup() returns false for the device, it
+ * will not be enabled to generate wakeup events.
+ */
+int pci_enable_wake(struct pci_dev *pci_dev, pci_power_t state, bool enable)
+{
+	if (enable && !device_may_wakeup(&pci_dev->dev))
+		return -EINVAL;
+
+	return __pci_enable_wake(pci_dev, state, enable);
+}
 EXPORT_SYMBOL(pci_enable_wake);
 
 /**
@@ -1981,9 +1998,9 @@ EXPORT_SYMBOL(pci_enable_wake);
  * should not be called twice in a row to enable wake-up due to PCI PM vs ACPI
  * ordering constraints.
  *
- * This function only returns error code if the device is not capable of
- * generating PME# from both D3_hot and D3_cold, and the platform is unable to
- * enable wake-up power for it.
+ * This function only returns error code if the device is not allowed to wake
+ * up the system from sleep or it is not capable of generating PME# from both
+ * D3_hot and D3_cold and the platform is unable to enable wake-up power for it.
  */
 int pci_wake_from_d3(struct pci_dev *dev, bool enable)
 {
@@ -2114,12 +2131,12 @@ int pci_finish_runtime_suspend(struct pc
 
 	dev->runtime_d3cold = target_state == PCI_D3cold;
 
-	pci_enable_wake(dev, target_state, pci_dev_run_wake(dev));
+	__pci_enable_wake(dev, target_state, pci_dev_run_wake(dev));
 
 	error = pci_set_power_state(dev, target_state);
 
 	if (error) {
-		pci_enable_wake(dev, target_state, false);
+		__pci_enable_wake(dev, target_state, false);
 		dev->runtime_d3cold = false;
 	}