> On May 22, 2019, at 9:48 PM, Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote: > > On Wed, May 22, 2019 at 11:42:14AM +0800, Kai Heng Feng wrote: >> at 6:23 AM, Bjorn Helgaas <helgaas@xxxxxxxxxx> wrote: >>> On Wed, May 22, 2019 at 12:31:04AM +0800, Kai-Heng Feng wrote: >>>> There's an xHC device that doesn't wake when a USB device gets plugged >>>> to its USB port. The driver's own runtime suspend callback was called, >>>> PME signaling was enabled, but it stays at PCI D0. >>> >>> This looks like it's fixing a bug? If so, please include a link to >>> the bug report, and make sure the bug report has "lspci -vv" output >>> attached to it. > > I see your bug report (https://bugzilla.kernel.org/show_bug.cgi?id=203673) > but it doesn't say anything about what this looks like to a user. > Presumably somebody complained about something not working. The bug > report should include that information about what isn't working. > Ideally, a user experiencing a problem should be able to google for > the symptoms and find the bug report. Sorry about that. I’ve added a comment to describe the symptom. > >>>> A PCI device can be runtime suspended to D0 when it supports D0 PME and >>>> its _S0W reports D0. Theoratically this should work, but as [1] >>>> specifies, D0 doesn't have wakeup capability. >>> >>> What does "runtime suspended to D0" mean? > > If I understand correctly, Linux normally clears PME-Enable while > devices are in D0, but sets PME-Enable if a device is "runtime > suspended to D0”. Yes, this is what happens here. > > I'm not sure I'd describe that as "suspended", since the power > management state is exactly D0 and the only difference is that a PME > interrupt is enabled. It sounds to me like the xHCI controller is > basically using PME as a hotplug interrupt to say "something happened > on my secondary (USB) interface". But that's more a question for > Rafael. Runtime suspend routines are called successfully, so I think it’s still logically suspended. > > And I guess this patch basically means we wouldn't call the driver's > suspend callback if we're merely going to stay at D0, so the driver > would have no idea anything happened. That might match > Documentation/power/pci.txt better, because it suggests that the > suspend callback is related to putting a device in a low-power state, > and D0 is not a low-power state. Yes, the patch is to let the device stay at D0 and don’t run driver’s own runtime suspend routine. I guess I’ll just proceed to send a V2 with updated commit message? Kai-Heng > > Maybe we should also update Documentation/power/pci.txt to say "PCI > devices ... can be programmed to generate PMEs while in any state > (D0-D3)" instead of "a low-power state (D1-D3)”. > > Anyway, this is all Rafael's area, so I'll defer to him. > >>>> Signed-off-by: Kai-Heng Feng <kai.heng.feng@xxxxxxxxxxxxx> >>>> --- >>>> drivers/pci/pci-driver.c | 5 +++++ >>>> drivers/pci/pci.c | 2 +- >>>> include/linux/pci.h | 3 +++ >>>> 3 files changed, 9 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c >>>> index cae630fe6387..15a6310c5d7b 100644 >>>> --- a/drivers/pci/pci-driver.c >>>> +++ b/drivers/pci/pci-driver.c >>>> @@ -1251,6 +1251,11 @@ static int pci_pm_runtime_suspend(struct >>>> device *dev) >>>> return 0; >>>> } >>>> >>>> + if (pci_target_state(pci_dev, device_can_wakeup(dev)) == PCI_D0) { >>>> + dev_dbg(dev, "D0 doesn't have wakeup capability\n"); >>>> + return -EBUSY; >>>> + } >>>> + >>>> pci_dev->state_saved = false; >>>> if (pm && pm->runtime_suspend) { >>>> error = pm->runtime_suspend(dev); >>>> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c >>>> index 8abc843b1615..ceee6efbbcfe 100644 >>>> --- a/drivers/pci/pci.c >>>> +++ b/drivers/pci/pci.c >>>> @@ -2294,7 +2294,7 @@ EXPORT_SYMBOL(pci_wake_from_d3); >>>> * If the platform can't manage @dev, return the deepest state from which it >>>> * can generate wake events, based on any available PME info. >>>> */ >>>> -static pci_power_t pci_target_state(struct pci_dev *dev, bool wakeup) >>>> +pci_power_t pci_target_state(struct pci_dev *dev, bool wakeup) >>>> { >>>> pci_power_t target_state = PCI_D3hot; >>>> >>>> diff --git a/include/linux/pci.h b/include/linux/pci.h >>>> index 4a5a84d7bdd4..91e8dc4d04aa 100644 >>>> --- a/include/linux/pci.h >>>> +++ b/include/linux/pci.h >>>> @@ -1188,6 +1188,7 @@ bool pci_pme_capable(struct pci_dev *dev, >>>> pci_power_t state); >>>> void pci_pme_active(struct pci_dev *dev, bool enable); >>>> int pci_enable_wake(struct pci_dev *dev, pci_power_t state, bool enable); >>>> int pci_wake_from_d3(struct pci_dev *dev, bool enable); >>>> +pci_power_t pci_target_state(struct pci_dev *dev, bool wakeup); >>>> int pci_prepare_to_sleep(struct pci_dev *dev); >>>> int pci_back_from_sleep(struct pci_dev *dev); >>>> bool pci_dev_run_wake(struct pci_dev *dev); >>>> @@ -1672,6 +1673,8 @@ static inline int pci_set_power_state(struct >>>> pci_dev *dev, pci_power_t state) >>>> { return 0; } >>>> static inline int pci_wake_from_d3(struct pci_dev *dev, bool enable) >>>> { return 0; } >>>> +pci_power_t pci_target_state(struct pci_dev *dev, bool wakeup) >>>> +{ return PCI_D0; } >>>> static inline pci_power_t pci_choose_state(struct pci_dev *dev, >>>> pm_message_t state) >>>> { return PCI_D0; } >>>> -- >>>> 2.17.1 >> >>
