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

[Denis Benato <benato.denis96@gmail.com>]

On 17/01/25 21:31, 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@canonical.com>
>> Reviewed-by: Mario Limonciello <mario.limonciello@amd.com>
>> Tested-by: Mario Limonciello <mario.limonciello@amd.com>
>> Signed-off-by: Kai-Heng Feng <kaihengf@nvidia.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@squebb.ca>
> 
> Mark

Hello,

I have helped an user affected by the issue this patch solves (FA507NV).

The issue has been solved by this patch.

I also tested this patch with two unaffected laptops: my own (G634JZ) and my brother's (FX507ZE): neither showed sign of any regressions.

Tested-by: Merthan Karakaş <m3rthn.k@gmail.com>
Tested-by: Denis Benato <benato.denis96@gmail.com>