[PATCH 6/9] PM / ACPI: Provide option to disable direct_complete for ACPI devices

[Rafael J. Wysocki]

On Wed, Jun 21, 2017 at 9:21 PM, Ulf Hansson <ulf.hansson at linaro.org> wrote:
> In some cases a driver for an ACPI device needs to be able to prevent the
> ACPI PM domain from using the direct_complete path during system sleep.
>
> One typical case is when the driver for the device needs its device to stay
> runtime enabled, during the __device_suspend phase. This isn't the case
> when the direct_complete path is being executed by the PM core, as it then
> disables runtime PM for the device in __device_suspend(). Any following
> attempts to runtime resume the device after that point, just fails.
>
> A workaround to this problem is to let the driver runtime resume its device
> from its ->prepare() callback, as that would prevent the direct_complete
> path from being executed. However, that may often be a waste, especially if
> it turned out that no one really needed the device.
>
> For this reason, invent acpi_dev_disable|enable_direct_complete(), to allow
> drivers to inform the ACPI PM domain to change its default behaviour during
> system sleep, and thus control whether it may use the direct_complete path
> or not.
>
> Typically a driver should call acpi_dev_disable_direct_comlete() during
> ->probe() and acpi_dev_enable_direct_complete() in ->remove().
>
> Signed-off-by: Ulf Hansson <ulf.hansson at linaro.org>
> ---
>  drivers/acpi/device_pm.c | 37 ++++++++++++++++++++++++++++++++++++-
>  include/acpi/acpi_bus.h  |  1 +
>  include/linux/acpi.h     |  4 ++++
>  3 files changed, 41 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/acpi/device_pm.c b/drivers/acpi/device_pm.c
> index ee51e75..2393a1a 100644
> --- a/drivers/acpi/device_pm.c
> +++ b/drivers/acpi/device_pm.c
> @@ -879,6 +879,41 @@ EXPORT_SYMBOL_GPL(acpi_subsys_runtime_resume);
>
>  #ifdef CONFIG_PM_SLEEP
>  /**
> + * acpi_dev_disable_direct_complete - Disable the direct_complete path for ACPI.
> + * @dev: Device to disable the path for.
> + *
> + * Per default the ACPI PM domain tries to use the direct_complete path for its
> + * devices during system sleep. This function allows a user, typically a driver
> + * during probe, to disable the direct_complete path from being used by ACPI.
> + */
> +void acpi_dev_disable_direct_complete(struct device *dev)
> +{
> +       struct acpi_device *adev = ACPI_COMPANION(dev);
> +
> +       if (adev)
> +               adev->no_direct_complete = true;

We have an analogous flag in PCI now and it is called needs_resume, so
it would be good to be consistent with that.

> +}
> +EXPORT_SYMBOL_GPL(acpi_dev_disable_direct_complete);
> +
> +/**
> + * acpi_dev_enable_direct_complete - Enable the direct_complete path for ACPI.
> + * @dev: Device to enable the path for.
> + *
> + * Enable the direct_complete path to be used during system suspend for the ACPI
> + * PM domain, which is the default option. Typically a driver that disabled the
> + * path during ->probe(), must call this function during ->remove() to re-enable
> + * the direct_complete path to be used by ACPI.
> + */
> +void acpi_dev_enable_direct_complete(struct device *dev)
> +{
> +       struct acpi_device *adev = ACPI_COMPANION(dev);
> +
> +       if (adev)
> +               adev->no_direct_complete = false;
> +}
> +EXPORT_SYMBOL_GPL(acpi_dev_enable_direct_complete);
> +
> +/**
>   * acpi_dev_suspend_late - Put device into a low-power state using ACPI.
>   * @dev: Device to put into a low-power state.
>   *
> @@ -967,7 +1002,7 @@ int acpi_subsys_prepare(struct device *dev)
>         if (ret < 0)
>                 return ret;
>
> -       if (!adev || !pm_runtime_suspended(dev))
> +       if (!adev || adev->no_direct_complete || !pm_runtime_suspended(dev))
>                 return 0;
>
>         return !acpi_dev_needs_resume(dev, adev);
> diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
> index 63a90a6..2293d24 100644
> --- a/include/acpi/acpi_bus.h
> +++ b/include/acpi/acpi_bus.h
> @@ -380,6 +380,7 @@ struct acpi_device {
>         struct list_head physical_node_list;
>         struct mutex physical_node_lock;
>         void (*remove)(struct acpi_device *);
> +       bool no_direct_complete;

Also what about adding this to struct acpi_device_power instead?

Thanks,
Rafael