Re: [PATCH][v3] PCI / PM: Avoid resuming PCI devices during system suspend

[Bjorn Helgaas]

On Tue, Jan 20, 2015 at 7:17 PM, Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
>
> Commit f25c0ae2b4c4 (ACPI / PM: Avoid resuming devices in ACPI PM
> domain during system suspend) modified the ACPI PM domain's system
> suspend callbacks to allow devices attached to it to be left in the
> runtime-suspended state during system suspend so as to optimize
> the suspend process.
>
> This was based on the general mechanism introduced by commit
> aae4518b3124 (PM / sleep: Mechanism to avoid resuming runtime-suspended
> devices unnecessarily).
>
> Extend that approach to PCI devices by modifying the PCI bus type's
> ->prepare callback to return 1 for devices that are runtime-suspended
> when it is being executed and that are in a suitable power state and
> need not be resumed going forward.
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>

I don't profess to understand this, and it seems like something you
could merge via your PM tree.  So I trust you to do the right thing
with it :)

Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>

> ---
>
> This version actually builds and need not be an RFC any more I suppose.
>
> ---
>  drivers/pci/pci-acpi.c   |   17 +++++++++++++++++
>  drivers/pci/pci-driver.c |   11 ++++++-----
>  drivers/pci/pci.c        |   26 ++++++++++++++++++++++++++
>  drivers/pci/pci.h        |    6 ++++++
>  4 files changed, 55 insertions(+), 5 deletions(-)
>
> Index: linux-pm/drivers/pci/pci.c
> ===================================================================
> --- linux-pm.orig/drivers/pci/pci.c
> +++ linux-pm/drivers/pci/pci.c
> @@ -521,6 +521,11 @@ static inline int platform_pci_run_wake(
>                         pci_platform_pm->run_wake(dev, enable) : -ENODEV;
>  }
>
> +static inline bool platform_pci_need_resume(struct pci_dev *dev)
> +{
> +       return pci_platform_pm ? pci_platform_pm->need_resume(dev) : false;
> +}
> +
>  /**
>   * pci_raw_set_power_state - Use PCI PM registers to set the power state of
>   *                           given PCI device
> @@ -1999,6 +2004,27 @@ bool pci_dev_run_wake(struct pci_dev *de
>  }
>  EXPORT_SYMBOL_GPL(pci_dev_run_wake);
>
> +/**
> + * pci_dev_keep_suspended - Check if the device can stay in the suspended state.
> + * @pci_dev: Device to check.
> + *
> + * Return 'true' if the device is runtime-suspended, it doesn't have to be
> + * reconfigured due to wakeup settings difference between system and runtime
> + * suspend and the current power state of it is suitable for the upcoming
> + * (system) transition.
> + */
> +bool pci_dev_keep_suspended(struct pci_dev *pci_dev)
> +{
> +       struct device *dev = &pci_dev->dev;
> +
> +       if (!pm_runtime_suspended(dev)
> +           || (device_can_wakeup(dev) && !device_may_wakeup(dev))
> +           || platform_pci_need_resume(pci_dev))
> +               return false;
> +
> +       return pci_target_state(pci_dev) == pci_dev->current_state;
> +}
> +
>  void pci_config_pm_runtime_get(struct pci_dev *pdev)
>  {
>         struct device *dev = &pdev->dev;
> Index: linux-pm/drivers/pci/pci.h
> ===================================================================
> --- linux-pm.orig/drivers/pci/pci.h
> +++ linux-pm/drivers/pci/pci.h
> @@ -50,6 +50,10 @@ int pci_probe_reset_function(struct pci_
>   *             for given device (the device's wake-up capability has to be
>   *             enabled by @sleep_wake for this feature to work)
>   *
> + * @need_resume: returns 'true' if the given device (which is currently
> + *             suspended) needs to be resumed to be configured for system
> + *             wakeup.
> + *
>   * If given platform is generally capable of power managing PCI devices, all of
>   * these callbacks are mandatory.
>   */
> @@ -59,6 +63,7 @@ struct pci_platform_pm_ops {
>         pci_power_t (*choose_state)(struct pci_dev *dev);
>         int (*sleep_wake)(struct pci_dev *dev, bool enable);
>         int (*run_wake)(struct pci_dev *dev, bool enable);
> +       bool (*need_resume)(struct pci_dev *dev);
>  };
>
>  int pci_set_platform_pm(struct pci_platform_pm_ops *ops);
> @@ -67,6 +72,7 @@ void pci_power_up(struct pci_dev *dev);
>  void pci_disable_enabled_device(struct pci_dev *dev);
>  int pci_finish_runtime_suspend(struct pci_dev *dev);
>  int __pci_pme_wakeup(struct pci_dev *dev, void *ign);
> +bool pci_dev_keep_suspended(struct pci_dev *dev);
>  void pci_config_pm_runtime_get(struct pci_dev *dev);
>  void pci_config_pm_runtime_put(struct pci_dev *dev);
>  void pci_pm_init(struct pci_dev *dev);
> Index: linux-pm/drivers/pci/pci-acpi.c
> ===================================================================
> --- linux-pm.orig/drivers/pci/pci-acpi.c
> +++ linux-pm/drivers/pci/pci-acpi.c
> @@ -501,12 +501,29 @@ static int acpi_pci_run_wake(struct pci_
>         return 0;
>  }
>
> +static bool acpi_pci_need_resume(struct pci_dev *dev)
> +{
> +       struct acpi_device *adev = ACPI_COMPANION(&dev->dev);
> +
> +       if (!adev || !acpi_device_power_manageable(adev))
> +               return false;
> +
> +       if (device_may_wakeup(&dev->dev) != !!adev->wakeup.prepare_count)
> +               return true;
> +
> +       if (acpi_target_system_state() == ACPI_STATE_S0)
> +               return false;
> +
> +       return !!adev->power.flags.dsw_present;
> +}
> +
>  static struct pci_platform_pm_ops acpi_pci_platform_pm = {
>         .is_manageable = acpi_pci_power_manageable,
>         .set_state = acpi_pci_set_power_state,
>         .choose_state = acpi_pci_choose_state,
>         .sleep_wake = acpi_pci_sleep_wake,
>         .run_wake = acpi_pci_run_wake,
> +       .need_resume = acpi_pci_need_resume,
>  };
>
>  void acpi_pci_add_bus(struct pci_bus *bus)
> Index: linux-pm/drivers/pci/pci-driver.c
> ===================================================================
> --- linux-pm.orig/drivers/pci/pci-driver.c
> +++ linux-pm/drivers/pci/pci-driver.c
> @@ -653,7 +653,6 @@ static bool pci_has_legacy_pm_support(st
>  static int pci_pm_prepare(struct device *dev)
>  {
>         struct device_driver *drv = dev->driver;
> -       int error = 0;
>
>         /*
>          * Devices having power.ignore_children set may still be necessary for
> @@ -662,10 +661,12 @@ static int pci_pm_prepare(struct device
>         if (dev->power.ignore_children)
>                 pm_runtime_resume(dev);
>
> -       if (drv && drv->pm && drv->pm->prepare)
> -               error = drv->pm->prepare(dev);
> -
> -       return error;
> +       if (drv && drv->pm && drv->pm->prepare) {
> +               int error = drv->pm->prepare(dev);
> +               if (error)
> +                       return error;
> +       }
> +       return pci_dev_keep_suspended(to_pci_dev(dev));
>  }
>
>
>
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