Re: [PATCH 1/2] PCI: Avoid runtime resuming devices if system is shutting down

Rafael J. Wysocki
2023-12-13T18:31:28Z

On Wed, Dec 13, 2023 at 7:27 PM Mario Limonciello
<mario.limonciello@amd.com> wrote:
>
> When the system is going to S5 resuming devices is unnecessary at
> best and may cause problems for power consumption at S5 at worst.
>
> Check the target `system_state` in the pci driver shutdown() callback
> and skip the runtime resume step if the system is being powered off.
>
> Cc: mpearson-lenovo@squebb.ca
> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
> ---
> drivers/pci/pci-driver.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
> index 51ec9e7e784f..5a6f7a786952 100644
> --- a/drivers/pci/pci-driver.c
> +++ b/drivers/pci/pci-driver.c
> @@ -507,7 +507,9 @@ static void pci_device_shutdown(struct device *dev)
> struct pci_dev *pci_dev = to_pci_dev(dev);
> struct pci_driver *drv = pci_dev->driver;
>
> - pm_runtime_resume(dev);
> + /* If system will go to S5, don't wake up PCI devices for shutdown */
> + if (system_state != SYSTEM_POWER_OFF)
> + pm_runtime_resume(dev);

What's the guarantee that the driver's shutdown callback will not
access MMIO regions of a runtime-suspended device?

> if (drv && drv->shutdown)
> drv->shutdown(pci_dev);
> --