linux-kernel - Re: [PATCH v2] PCI/PM: Put devices to low power state on shutdown'

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Message-ID: <f95750db-a857-4ba3-9c2d-c48caa9ff16e@kernel.org>
Date: Tue, 22 Apr 2025 10:18:46 -0500
From: Mario Limonciello <superm1@...nel.org>
To: "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc: bhelgaas@...gle.com, mika.westerberg@...ux.intel.com,
 linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
 AceLan Kao <acelan.kao@...onical.com>, linux-pm@...r.kernel.org,
 Kai-Heng Feng <kaihengf@...dia.com>, Bjorn Helgaas <helgaas@...nel.org>
Subject: Re: [PATCH v2] PCI/PM: Put devices to low power state on shutdown'

On 2/19/2025 12:46 PM, Bjorn Helgaas wrote:
> [+to Rafael, +cc linux-pm]
> 
> On Sun, Dec 08, 2024 at 03:41:47PM +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.
> 
> aer_remove() disables AER interrupts, so I guess there must be a
> non-AER interrupt being generated during shutdown?
> 
> If so, AER is a red herring and including the AER details above is a
> distraction from whatever the real interrupt cause is.
> 
>> 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.
>>
>> ACPI Spec 6.5, "7.4.2.5 System \_S4 State" says "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."
>>
>> The following "7.4.2.6 System \_S5 State (Soft Off)" states "The S5
>> state is similar to the S4 state except that OSPM does not save any
>> context." so it's safe to assume devices should be at D3 for S5.
>>
>> Link: https://bugzilla.kernel.org/show_bug.cgi?id=219036
>> Cc: AceLan Kao <acelan.kao@...onical.com>
>> Reviewed-by: Mario Limonciello <mario.limonciello@....com>
>> Tested-by: Mario Limonciello <mario.limonciello@....com>
>> Signed-off-by: Kai-Heng Feng <kaihengf@...dia.com>
>> ---
>>   drivers/pci/pci-driver.c | 8 ++++++++
>>   1 file changed, 8 insertions(+)
>>
>> diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
>> index 35270172c833..248e0c9fd161 100644
>> --- a/drivers/pci/pci-driver.c
>> +++ b/drivers/pci/pci-driver.c
>> @@ -510,6 +510,14 @@ static void pci_device_shutdown(struct device *dev)
>>   	if (drv && drv->shutdown)
>>   		drv->shutdown(pci_dev);
>>   
>> +	/*
>> +	 * If driver already changed device's power state, it can mean the
>> +	 * wakeup setting is in place, or a workaround is used. Hence keep it
>> +	 * as is.
>> +	 */
>> +	if (!kexec_in_progress && pci_dev->current_state == PCI_D0)
>> +		pci_prepare_to_sleep(pci_dev);
> 
> 
> I don't know enough to draw inferences about PCI_D0 meaning a wakeup
> setting is in place or a workaround being used.  That doesn't seem
> like enough to be useful for me to maintain this in the future.  But
> my power management understanding is pretty meager.
> 
> Would like an ack from Rafael for this.

Rafael,

Can you take a look at this patch and provide your thoughts?

Thanks!
> 
>>   	/*
>>   	 * If this is a kexec reboot, turn off Bus Master bit on the
>>   	 * device to tell it to not continue to do DMA. Don't touch
>> -- 
>> 2.47.0
>>
>