linux-kernel - Re: [PATCH] PCI / ACPI: Don't clear pme_poll on device that has unreliable ACPI wake

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Message-ID: <20190204172057.GB9160@google.com>
Date:   Mon, 4 Feb 2019 11:20:57 -0600
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Kai Heng Feng <kai.heng.feng@...onical.com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>, jeffrey.t.kirsher@...el.com,
        intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
        linux-acpi@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI / ACPI: Don't clear pme_poll on device that has
 unreliable ACPI wake

On Sun, Feb 03, 2019 at 01:46:50AM +0800, Kai Heng Feng wrote:
> > On Jan 28, 2019, at 3:51 PM, Kai Heng Feng <kai.heng.feng@...onical.com> wrote:
> 
> >> If I understand correctly, the bugzilla lspci
> >> (https://bugzilla.kernel.org/attachment.cgi?id=280691) was collected
> >> at point 8, and it shows PME_Status=1 when it should be 0.
> >> 
> >> If we write a 1 to PME_Status to clear it, and it remains set, that's
> >> obviously a hardware defect, and Intel should document that in an
> >> erratum, and a quirk would be the appropriate way to work around it.
> >> But I doubt that's what's happening.
> > 
> > I’ll ask them if they can provide an erratum.
> 
> Got confirmed with e1000e folks, I219 (the device in question) doesn’t
> really support runtime D3.

Did you get a reference, e.g., an intel.com URL for that?  Intel
usually publishes errata for hardware defects, which is nice because
it means every customer doesn't have to experimentally rediscover
them.

> I also checked the behavior of the device under Windows, and it
> stays at D0 all the time even when it’s not in use.

I think there are two possible explanations for this:

  1) This device requires a Windows or a driver update with a
  device-specific quirk similar to what you're proposing for Linux.

  2) Windows correctly detects that this device doesn't support D3,
  and Linux has a bug and does not detect that.

Obviously nobody wants to require OS or driver updates just for minor
device changes, and the PCI and ACPI specs are designed to allow
generic, non device-specific code to detect D3 support, so the first
case should be a result of a hardware defect.

> So I sent a patch [1] to disable it.
> 
> [1] https://lkml.org/lkml/2019/2/2/200

OK.  Since that's in drivers/net/..., I have no objection and the
e1000e maintainers would deal with that.

Bjorn