linux-kernel - Re: [PATCH 2/2] PCI/portdrv: Place PCIe port hierarchy into D3cold at shutdown

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Message-ID: <766d621c-695d-4ae7-87cf-690cb8d066df@amd.com>
Date:   Wed, 13 Dec 2023 12:42:04 -0600
From:   Mario Limonciello <mario.limonciello@....com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     Bjorn Helgaas <bhelgaas@...gle.com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        linux-pci@...r.kernel.org, linux-acpi@...r.kernel.org,
        linux-kernel@...r.kernel.org, mpearson-lenovo@...ebb.ca
Subject: Re: [PATCH 2/2] PCI/portdrv: Place PCIe port hierarchy into D3cold at
 shutdown

On 12/13/2023 12:38, Rafael J. Wysocki wrote:
> On Wed, Dec 13, 2023 at 7:27 PM Mario Limonciello
> <mario.limonciello@....com> wrote:
>>
>> When a system is being powered off it's important that PCIe ports
>> have been put into D3cold as there is no other software to turn
>> off the devices at S5.
>>
>> If PCIe ports are left in D0 then any GPIOs toggled by the ACPI
>> power resources may be left enabled and devices may consume excess
>> power.
> 
> Isn't that a platform firmware issue?
> 
> It is the responsibility of the platform firmware to properly put the
> platform into S5, including power removal from devices that are not
> armed for power-on.

The specific issues that triggered this series were tied to the PCIe 
ports for dGPUs.  There is a GPIO that is toggled by _ON or _OFF.

Windows calls _OFF as part of S5..

> 
>> Cc: mpearson-lenovo@...ebb.ca
>> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
>> ---
>>   drivers/pci/pcie/portdrv.c | 11 ++++++++---
>>   1 file changed, 8 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/pci/pcie/portdrv.c b/drivers/pci/pcie/portdrv.c
>> index 14a4b89a3b83..08238680c481 100644
>> --- a/drivers/pci/pcie/portdrv.c
>> +++ b/drivers/pci/pcie/portdrv.c
>> @@ -734,9 +734,14 @@ static void pcie_portdrv_remove(struct pci_dev *dev)
>>   static void pcie_portdrv_shutdown(struct pci_dev *dev)
>>   {
>>          if (pci_bridge_d3_possible(dev)) {
>> -               pm_runtime_forbid(&dev->dev);
>> -               pm_runtime_get_noresume(&dev->dev);
>> -               pm_runtime_dont_use_autosuspend(&dev->dev);
>> +               /* whole hierarchy goes into a low power state for S5 */
>> +               if (system_state == SYSTEM_POWER_OFF) {
>> +                       pci_set_power_state(dev, PCI_D3cold);
>> +               } else {
>> +                       pm_runtime_forbid(&dev->dev);
>> +                       pm_runtime_get_noresume(&dev->dev);
>> +                       pm_runtime_dont_use_autosuspend(&dev->dev);
>> +               }
>>          }
> 
> Wouldn't it be better to remove power from the port after running the
> code below?
> 

Yes; I think you're right.  I'll do some more testing with this.

>>          pcie_port_device_remove(dev);
>> --