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

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Date:   Mon, 18 Feb 2019 16:30:35 +0100
From:   Kai Heng Feng <kai.heng.feng@...onical.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
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 Feb 4, 2019, at 6:20 PM, Bjorn Helgaas <helgaas@...nel.org> wrote:
> 
> 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.

Unfortunately no.

> 
>> 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.

I am sure the latest driver is loaded under Windows.

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

I think that’s the case.

> 
> 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.

Yea, that’s why my original idea is to workaround it in PCI/ACPI.

> 
>> 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.

Thanks.

Kai-Heng

> 
> Bjorn