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

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Message-ID: <d914e3c5-f38c-4e2f-b46b-8edb1e8940d1@kernel.org>
Date: Tue, 18 Feb 2025 21:56:42 -0600
From: Mario Limonciello <superm1@...nel.org>
To: Bjorn Helgaas <bhelgaas@...gle.com>
Cc: linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
 AceLan Kao <acelan.kao@...onical.com>,
 "Limonciello, Mario" <mario.limonciello@....com>,
 Mark Pearson <mpearson-lenovo@...ebb.ca>, Kai-Heng Feng
 <kaihengf@...dia.com>, mika.westerberg@...ux.intel.com
Subject: Re: [PATCH v2] PCI/PM: Put devices to low power state on shutdown



On 1/17/25 14:31, Mark Pearson wrote:
> Hi,
> 
> On Sun, Dec 8, 2024, at 2:41 AM, 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.
>>
>> 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);
>> +
>>   	/*
>>   	 * 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
> 
> Just a note that we've tested this in the Lenovo Linux team and confirmed that it reduces the power draw on a powered off Z16 G2 by 0.6W.
> This is enough to bring Linux inline with Windows, and more importantly allow the platform to pass e-star energy certification (which it otherwise fails). We suspect other platforms will show similar benefits.
> 
> Let me know if there's anything we can do to help get this patch moving along - I think it's important.
> 
> Tested-by: Mark Pearson <mpearson-lenovo@...ebb.ca>
> 
> Mark
> 

Bjorn,

Anything else that you would like to see for this patch?
Or different direction you would like to see it go?

Thanks,