Re: bisected regression, v3.5 -> next-20120724: PCI PM causes USB hotplug failure

[Huang Ying <ying.huang@intel.com>]

Hi, Rafael,

On Wed, 2012-07-25 at 22:02 +0200, Rafael J. Wysocki wrote:
> On Wednesday, July 25, 2012, Bjørn Mork wrote:
> > huang ying <huang.ying.caritas@gmail.com> writes:
> > 
> > > Hi, Bjorn,
> > >
> > > Thank you very much for your detailed information.
> > >
> > > On Wed, Jul 25, 2012 at 5:58 PM, Bjørn Mork <bjorn@mork.no> wrote:
> > >> Huang Ying <ying.huang@intel.com> writes:
> > >>> On Wed, 2012-07-25 at 06:08 +0200, Bjørn Mork wrote:
> > >>>> Enabling autosuspend for USB causes hotplug failure in the current
> > >>>> linux-next. Newly plugged devices are not detected at all until the
> > >>>> port/controller is manually powered on by writing "on" to power/control.
> > >>>> Testing is pretty simple:
> > >>>>
> > >>>>   1) for f in /sys/bus/usb/devices/*/power/control; do echo auto > $f; done
> > >>>
> > >>> Have you done:
> > >>>
> > >>> for f in /sys/bus/pci/devices/*/power/confol; do echo auto > $f; done
> > >>>
> > >>> ?
> > >>>
> > >>> If not, the pci device will not be suspended at all.
> > >>
> > >> Yes, sorry for missing that.  I had it automatically enabled.  Yes,
> > >> autosuspend for the PCI device and all child devices must be enabled for
> > >> the device to be suspended at all, of course.
> > >>
> > >>>>   2) wait for the controllers to suspend
> > >>>>   3) plugin a new USB device
> > >>>
> > >>> After plugin the new USB device, is there anything in dmesg?
> > >>
> > >> No. Absolutely nothing, so the USB devices is not enumerated.  Another
> > >> indication of the same:  Plugging a device like an Android phone, which
> > >> normally detects being connected to a host and presents a device type
> > >> menu to the user, results in the charging LED lighting up but no menu.
> > >>
> > >>
> > >> Trying to show the sequence of events:
> > >>
> > >> 1)  the controllers are suspended:
> > >>
> > >> Jul 25 11:27:12 nemi kernel: [   38.962792] uhci_hcd 0000:00:1a.2: power state changed by ACPI to D2
> > >> Jul 25 11:27:12 nemi kernel: [   39.006718] uhci_hcd 0000:00:1d.0: power state changed by ACPI to D2
> > >> Jul 25 11:27:15 nemi kernel: [   41.808471] uhci_hcd 0000:00:1a.0: power state changed by ACPI to D2
> > >> Jul 25 11:27:15 nemi kernel: [   41.824123] ehci_hcd 0000:00:1a.7: power state changed by ACPI to D2
> > >> Jul 25 11:27:15 nemi kernel: [   41.824194] ehci_hcd 0000:00:1d.7: power state changed by ACPI to D2
> > >
> > > Here uhci controller is put into D2
> > >
> > > [snip]
> > >>
> > >> Doing the same with commit 448bd857d reverted:
> > >>
> > >>
> > >> 1)  the controllers are suspended (to state D3? instead of D2?):
> > >>
> > >> Jul 25 11:34:01 nemi kernel: [   37.064955] uhci_hcd 0000:00:1a.2: power state changed by ACPI to D3
> > >> Jul 25 11:34:01 nemi kernel: [   37.106586] uhci_hcd 0000:00:1d.0: power state changed by ACPI to D3
> > >> Jul 25 11:34:04 nemi kernel: [   39.808329] uhci_hcd 0000:00:1a.0: power state changed by ACPI to D3
> > >> Jul 25 11:34:04 nemi kernel: [   39.840054] ehci_hcd 0000:00:1d.7: power state changed by ACPI to D3
> > >> Jul 25 11:34:04 nemi kernel: [   39.840068] ehci_hcd 0000:00:1a.7: power state changed by ACPI to D3
> > >
> > > With commit reverted, the uhci_controller is put into D3 (ACPI D3cold).
> > >
> > > And the uhci controller on your system may not work properly under D2
> > > state, while OK in D3 state, and the commit will make uhci controller
> > > choose D2 instead of D3.
> > >
> > > Please try following command line before testing.
> > >
> > > for f in /sys/bus/pci/devices/*/d3cold_allowed; do echo 1 > $f; done
> > 
> > That made it work.  The USB controllers ended up in D4 though:
> > 
> > Jul 25 15:52:33 nemi kernel: [  152.753280] uhci_hcd 0000:00:1a.0: power state changed by ACPI to D0
> > Jul 25 15:52:33 nemi kernel: [  152.753453] uhci_hcd 0000:00:1a.0: setting latency timer to 64
> > Jul 25 15:52:33 nemi kernel: [  152.753619] uhci_hcd 0000:00:1a.0: power state changed by ACPI to D4
> > Jul 25 15:52:33 nemi kernel: [  152.753875] uhci_hcd 0000:00:1a.1: setting latency timer to 64
> > Jul 25 15:52:33 nemi kernel: [  152.754153] uhci_hcd 0000:00:1a.2: power state changed by ACPI to D0
> > Jul 25 15:52:33 nemi kernel: [  152.754279] uhci_hcd 0000:00:1a.2: setting latency timer to 64
> > Jul 25 15:52:33 nemi kernel: [  152.754432] uhci_hcd 0000:00:1a.2: power state changed by ACPI to D4
> > Jul 25 15:52:33 nemi kernel: [  152.754668] ehci_hcd 0000:00:1a.7: setting latency timer to 64
> > Jul 25 15:52:33 nemi kernel: [  152.768089] ehci_hcd 0000:00:1a.7: power state changed by ACPI to D4
> > Jul 25 15:52:33 nemi kernel: [  152.768573] uhci_hcd 0000:00:1d.0: power state changed by ACPI to D0
> > Jul 25 15:52:33 nemi kernel: [  152.768726] uhci_hcd 0000:00:1d.0: setting latency timer to 64
> > Jul 25 15:52:33 nemi kernel: [  152.768891] uhci_hcd 0000:00:1d.0: power state changed by ACPI to D4
> > Jul 25 15:52:33 nemi kernel: [  152.769144] uhci_hcd 0000:00:1d.1: setting latency timer to 64
> > Jul 25 15:52:33 nemi kernel: [  152.769530] uhci_hcd 0000:00:1d.2: setting latency timer to 64
> > Jul 25 15:52:33 nemi kernel: [  152.769902] ehci_hcd 0000:00:1d.7: setting latency timer to 64
> > Jul 25 15:52:33 nemi kernel: [  152.784189] ehci_hcd 0000:00:1d.7: power state changed by ACPI to D4
> > 
> > 
> > was that expected?  Anyway, waking up the controller from this state by
> > plugging a USB device works, so it's a perfectly OK workaround.  Is this
> > something that could/should be implemented as a system specific quirk,
> > or is the problem more generic?  Even if it is a ACPI implementation
> > issue I would expect it to be common to a number of Lenovo laptops of
> > the same generation as mine (~2008).
> > 
> > > And please provide the output of the following command line.
> > >
> > > acpidump
> > 
> > Attached.  Thanks a lot for all your help debugging this issue.
> 
> This is not really necessary.  The problem is the change of behavior I was
> worried about some time ago.
> 
> Namely, the device in question apparently doesn't support ACPI D3_hot,
> so acpi_pm_device_sleep_state() returns D2 as the target state, where it
> would return D3(cold) before the commit in question.
> 
> To fix the regression, we'd need to reverse the current initial value of
> the d3cold_allowed flag so that it is set to "true" by default and only
> set to "false" for devices where we suspect there may be problems with
> D3_cold (like PCI Express ports).

Yes.  This is a good way to fix this issue and keep original behavior
for most devices.  I will work out a fix.

Best Regards,
Huang Ying