linux-kernel - Re: [PATCH] PCI/PM: Put devices to low power state on shutdown

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Message-ID: <08bea3c9-89bc-4483-bcf0-81c298fce80b@amd.com>
Date: Thu, 12 Sep 2024 08:10:00 -0500
From: Mario Limonciello <mario.limonciello@....com>
To: Kai-Heng Feng <kai.heng.feng@...onical.com>
Cc: Bjorn Helgaas <helgaas@...nel.org>, bhelgaas@...gle.com,
 mika.westerberg@...ux.intel.com, linux-pci@...r.kernel.org,
 linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org, kaihengfeng@...il.com
Subject: Re: [PATCH] PCI/PM: Put devices to low power state on shutdown

On 9/12/2024 02:02, Kai-Heng Feng wrote:
> On Thu, Sep 12, 2024 at 3:38 AM Mario Limonciello
> <mario.limonciello@....com> wrote:
>>
>> On 9/11/2024 14:16, Mario Limonciello wrote:
>>> On 9/11/2024 14:05, Bjorn Helgaas wrote:
>>>> On Fri, Jul 12, 2024 at 02:24:11PM +0800, Kai-Heng Feng wrote:
>>>>> Some laptops wake up after poweroff when HP Thunderbolt Dock G4 is
>>>>> connected.
>>>>>
>>>>> The following error message can be found during shutdown:
>>>>> pcieport 0000:00:1d.0: AER: Correctable error message received from
>>>>> 0000:09:04.0
>>>>> pcieport 0000:09:04.0: PCIe Bus Error: severity=Correctable,
>>>>> type=Data Link Layer, (Receiver ID)
>>>>> pcieport 0000:09:04.0:   device [8086:0b26] error
>>>>> status/mask=00000080/00002000
>>>>> pcieport 0000:09:04.0:    [ 7] BadDLLP
>>>>>
>>>>> Calling aer_remove() during shutdown can quiesce the error message,
>>>>> however the spurious wakeup still happens.
>>>>>
>>>>> The issue won't happen if the device is in D3 before system shutdown, so
>>>>> putting device to low power state before shutdown to solve the issue.
>>>>>
>>>>> I don't have a sniffer so this is purely guesswork, however I believe
>>>>> putting device to low power state it's the right thing to do.
>>>>
>>>> My objection here is that we don't have an explanation of why this
>>>> should matter or a pointer to any spec language about this situation,
>>>> so it feels a little bit random.
>>>>
>>>> I suppose the problem wouldn't happen if AER interrupts were disabled?
>>>> We already do disable them in aer_suspend(), but maybe that's not used
>>>> in the shutdown path?
>>>>
>>>> My understanding is that .shutdown() should turn off device interrupts
>>>> and stop DMA.  So maybe we need an aer_shutdown() that disables
>>>> interrupts?
>>>>
>>>
>>> IMO I see this commit as two problems with the same solution.
>>>
>>> I don't doubt that cleaning up AER interrupts in the shutdown path would
>>> help AER messages, but you really don't "want" devices to be in D0 when
>>> the system is "off" because even if the system is off some rails are
>>> still active and the device might still be powered.
>>>
>>> A powered device could cause interrupts (IE a spurious wakeup).
>>
>> It's a bit of a stretch, but ACPI 7.4.2.5 and 7.4.2.6 are the closest
>> corollary to a spec I can find.
>>
>> "Devices states are compatible with the current Power Resource states.
>> In other words, all devices are in the D3 state when the system state is
>> S4."
> 
> In addition to that, vendor collected the wave form from the device,
> Windows put the device to D3 while Linux kept the device in D0, and
> that asserted one of the PCIe interrupt line to cause system wakeup.
> 

I did the same collection and confirmed the state as well of many PCI 
devices on the system, elsewhere in this thread.

https://gist.github.com/superm1/f8f81e52f5b1d55b64493fdaec38e31c