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

[Kai-Heng Feng <kaihengf@nvidia.com>]

On 2025/5/7 1:32 AM, Mario Limonciello wrote:
> External email: Use caution opening links or attachments
> 
> 
> 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?

Alternatively, is it possible to put the change under '#ifdef CONFIG_ACPI' or 
'IS_ENABLED(CONFIG_ACPI)', so it won't affect anything other than ACPI based system?

Kai-Heng

> 
>>
>>> 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?

Kexec remains to work on my setup.

Kai-Heng

> 
>>
>>> ---
>>>   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
>>> -- 
>