Re: [PATCH v3] PCI/PM: Put devices to low power state on shutdown

[Mario Limonciello <superm1@kernel.org>]

On 5/6/2025 10:50 AM, Rafael J. Wysocki wrote:
> On Tue, May 6, 2025 at 6:19 AM Mario Limonciello <superm1@kernel.org> wrote:
>>
>> From: Kai-Heng Feng <kaihengf@nvidia.com>
>>
>> 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.
> 
> That's fine as long as you assume that ->shutdown() is only used for
> implementing ACPI S5, but it is not.

I suppose you're meaning things like:

kernel_restart_prepare()
->device_shutdown()
->->each device's shutdown() CB
->->each driver's shutdown() CB

Is there somewhere "better" to do this so it's truly only tied to 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>
>> Tested-by: Mark Pearson <mpearson-lenovo@squebb.ca>
>> Tested-by: Denis Benato <benato.denis96@gmail.com>
>> Tested-by: Merthan Karakaş <m3rthn.k@gmail.com>
>> Link: https://lore.kernel.org/r/20241208074147.22945-1-kaihengf@nvidia.com
>> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
>> ---
>> v3:
>>   * Pick up tags
>>   * V2 was waiting for Rafael to review, rebase on pci/next and resend.
> 
> Is this change going to break kexec?

There is an explicit check in the below code for kexec_in_progress, so 
my expectation was that kexec kept working.  I didn't explicitly test 
this myself when I tested KH's change before sending it again.

KH, Did you double check that on your side?

> 
>> ---
>>   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 0c5bdb8c2c07b..5bbe8af996390 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
>> --