r8169 Wake-on-LAN causes immediate ACPI GPE wakeup

[Daniel Drake]

Hi,

On the Acer laptop models Aspire ES1-533, Aspire ES1-732, PackardBell
ENTE69AP and Gateway NE533, we are seeing a problem where the system
immediately wakes up after being put into S3 suspend.

This problem has been seen on all kernel versions that we have tried,
including 4.14-rc3.

After disabling wakeup sources one by one, we found that the r8169
ethernet is responsible for these wakeups here, the hardware is:

01:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd.
RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 15)
    Subsystem: Acer Incorporated [ALI] Device 1084
    Flags: bus master, fast devsel, latency 0, IRQ 124
    I/O ports at 1000 [size=256]
    Memory at 91204000 (64-bit, non-prefetchable) [size=4K]
    Memory at 91200000 (64-bit, non-prefetchable) [size=16K]
    Capabilities: [40] Power Management version 3
    Capabilities: [50] MSI: Enable+ Count=1/1 Maskable- 64bit+
    Capabilities: [70] Express Endpoint, MSI 01
    Capabilities: [b0] MSI-X: Enable- Count=4 Masked-
    Capabilities: [100] Advanced Error Reporting
    Capabilities: [140] Virtual Channel
    Capabilities: [160] Device Serial Number 01-00-00-00-68-4c-e0-00
    Capabilities: [170] Latency Tolerance Reporting
    Capabilities: [178] L1 PM Substates
    Kernel driver in use: r8169

This driver enables WOL by default. The system wakes up immediately
when it is put into S3 suspend, even if there is no ethernet cable
plugged in.

The problem was also reproduced with the r8168 vendor driver, however
it does not occur under Windows, where we can suspend the system just
fine and also wake it up with a magic WOL packet.

Further investigation takes us into ACPI-land. The complete DSDT is here:
https://gist.github.com/dsd/62293b6d8c30a5204128709813a55ffb

Both Windows and Linux associate PCI0.RP05.PXSX with this device, so
let's consider this part of the DSDT:

  Device (RP05)
  {
      Method (_ADR, 0, NotSerialized)  // _ADR: Address
      {
          If (RPA5 != Zero)
          {
              Return (RPA5) /* \RPA5 */
          }
          Else
          {
              Return (0x00130002)
          }
      }

      Method (_PRW, 0, NotSerialized)  // _PRW: Power Resources for Wake
      {
          Return (GPRW (0x09, 0x04))
      }

      Device (PXSX)
      {
          Name (_ADR, Zero)  // _ADR: Address
          Name (_PRW, Package (0x02)  // _PRW: Power Resources for Wake
          {
              0x08,
              0x04
          })
      }

  }

RP05 corresponds to
00:13.0 PCI bridge: Intel Corporation Device 5ada (rev fb)

I am not familiar with this subdevice approach, where PXSX (with
address 0) is detected as a child of the PCI bridge, however both
Windows and Linux associate PXSX with the ethernet device, so I guess
it is correct.

Now to focus on the _PRW power resource for wakeup. The PXSX
(ethernet) device says that it will wake up the system using GPE08.
However if you look at the _L08 GPE08 event handler, you will see that
it does not do anything related to RP05/PXSX (it instead calls into
RP02, which does not even physically exist on this platform) -
suspicious.

On the other hand, the RP05 (root port) _PRW says it will wake up the
system via GPE09, and the _L09 handler at least has one codepath which
could potentially do a Notify(PXSX, 2) to indicate an ethernet wakeup.

But in testing:
 - If GPE08 is enabled as a wakeup source, the system will always wake
up as soon as it goes to sleep
 - I have never seen a wakeup on GPE09
 - Disabling GPE08 and all other GPE wakeups, the system sleeps fine,
and Wake-on-LAN works fine too

So in summary, the messy situation is that the DSDT suggests that
GPE08 will be used for ethernet wakeups, however that GPE seems to
fire instantly during suspend, and actually wake-on-LAN does not
appear to use ACPI GPEs to wake the system it all - it must use some
other mechanism. Windows is for some reason ignoring the ethernet
device _PRW information so it does not suffer this issue.

Does anyone have suggestions for how Linux should work with this?

What logic should we use to ignore the _PRW in this case, or how can
we quirk it?

Also, is there a standard behaviour defined for ethernet drivers
regarding wake-on-LAN? r8169 appears to enable wake-on-LAN by default
if it believes the hardware is capable of it, but other ethernet
drivers seem to default to WOL off. (I don't expect users of the
affected consumer laptops here to care about WOL support.)

Daniel