Re: [PATCH v2] PM / Sleep: Add pm_generic functions to re-use runtime PM callbacks

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On Monday, November 25, 2013 01:40:21 PM Ulf Hansson wrote:
> To put devices into low power state during sleep, it sometimes makes
> sense at subsystem-level to re-use device's runtime PM callbacks.
> 
> The PM core will at device_suspend_late disable runtime PM, after that
> we can safely operate on these callbacks. At suspend_late the device
> will be put into low power state by invoking the device's
> runtime_suspend callback, unless the runtime status is already
> suspended. At resume_early the state is restored by invoking the
> device's runtime_resume callback. Soon after the PM core will re-enable
> runtime PM before returning from device_resume_early.
> 
> The new pm_generic functions are named pm_generic_suspend_late_runtime
> and pm_generic_resume_early_runtime, they are supposed to be used in
> pairs.

What happens if the subsystem uses the new functions as its late suspend/
early resume callbacks, but some of its drivers implement .suspend_late()
and .resume_early()?

Also, these are system suspend/resume callbacks, so the "runtime" part of
the names is kind of confusing.  I have no idea for better naming at this
point, but still.

> Do note that these new generic callbacks will work smothly even with
> and without CONFIG_PM_RUNTIME, as long as the runtime PM callbacks are
> implemented inside CONFIG_PM instead of CONFIG_PM_RUNTIME.
> 
> A special thanks to Alan Stern who came up with this idea.
> 
> Cc: Kevin Hilman <khilman@xxxxxxxxxx>
> Cc: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
> ---
>  drivers/base/power/generic_ops.c |   86 ++++++++++++++++++++++++++++++++++++++
>  include/linux/pm.h               |    2 +
>  2 files changed, 88 insertions(+)
> 
> diff --git a/drivers/base/power/generic_ops.c b/drivers/base/power/generic_ops.c
> index 5ee030a..3132768 100644
> --- a/drivers/base/power/generic_ops.c
> +++ b/drivers/base/power/generic_ops.c
> @@ -93,6 +93,49 @@ int pm_generic_suspend_late(struct device *dev)
>  EXPORT_SYMBOL_GPL(pm_generic_suspend_late);
>  
>  /**
> + * pm_generic_suspend_late_runtime - Generic suspend_late callback for
> + * subsystems that wants to use runtime_suspend callbacks at suspend_late.

This has to be one line.  You can add more description below the @dev line.

> + * @dev: Device to suspend.
> + */
> +int pm_generic_suspend_late_runtime(struct device *dev)
> +{
> +	int (*callback)(struct device *);
> +	int ret = 0;
> +
> +	/*
> +	 * PM core has disabled runtime PM in device_suspend_late, thus we can
> +	 * safely check the device's runtime status and decide whether
> +	 * additional actions are needed to put the device into low power state.
> +	 * If so, we invoke the device's runtime_suspend callback.
> +	 * For the !CONFIG_PM_RUNTIME case, pm_runtime_status_suspended() always
> +	 * returns false and therefore the runtime_suspend callback will be
> +	 * invoked.
> +	 */
> +	if (pm_runtime_status_suspended(dev))
> +		return 0;
> +
> +	if (dev->pm_domain)
> +		callback = dev->pm_domain->ops.runtime_suspend;
> +	else if (dev->type && dev->type->pm)
> +		callback = dev->type->pm->runtime_suspend;
> +	else if (dev->class && dev->class->pm)
> +		callback = dev->class->pm->runtime_suspend;
> +	else if (dev->bus && dev->bus->pm)
> +		callback = dev->bus->pm->runtime_suspend;
> +	else
> +		callback = NULL;
> +
> +	if (!callback && dev->driver && dev->driver->pm)
> +		callback = dev->driver->pm->runtime_suspend;
> +
> +	if (callback)
> +		ret = callback(dev);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(pm_generic_suspend_late_runtime);
> +
> +/**
>   * pm_generic_suspend - Generic suspend callback for subsystems.
>   * @dev: Device to suspend.
>   */
> @@ -237,6 +280,49 @@ int pm_generic_resume_early(struct device *dev)
>  EXPORT_SYMBOL_GPL(pm_generic_resume_early);
>  
>  /**
> + * pm_generic_resume_early_runtime - Generic resume_early callback for
> + * subsystems that wants to use runtime_resume callbacks at resume_early.

Same here.

> + * @dev: Device to resume.
> + */
> +int pm_generic_resume_early_runtime(struct device *dev)
> +{
> +	int (*callback)(struct device *);
> +	int ret = 0;
> +
> +	/*
> +	 * PM core has not yet enabled runtime PM in device_resume_early,
> +	 * thus we can safely check the device's runtime status and restore the
> +	 * previous state we had in device_suspend_late. If restore is needed
> +	 * we invoke the device's runtime_resume callback.
> +	 * For the !CONFIG_PM_RUNTIME case, pm_runtime_status_suspended() always
> +	 * returns false and therefore the runtime_resume callback will be
> +	 * invoked.
> +	 */
> +	if (pm_runtime_status_suspended(dev))
> +		return 0;
> +
> +	if (dev->pm_domain)
> +		callback = dev->pm_domain->ops.runtime_resume;
> +	else if (dev->type && dev->type->pm)
> +		callback = dev->type->pm->runtime_resume;
> +	else if (dev->class && dev->class->pm)
> +		callback = dev->class->pm->runtime_resume;
> +	else if (dev->bus && dev->bus->pm)
> +		callback = dev->bus->pm->runtime_resume;
> +	else
> +		callback = NULL;
> +
> +	if (!callback && dev->driver && dev->driver->pm)
> +		callback = dev->driver->pm->runtime_resume;
> +
> +	if (callback)
> +		ret = callback(dev);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(pm_generic_resume_early_runtime);
> +
> +/**
>   * pm_generic_resume - Generic resume callback for subsystems.
>   * @dev: Device to resume.
>   */
> diff --git a/include/linux/pm.h b/include/linux/pm.h
> index a224c7f..5bce0d4 100644
> --- a/include/linux/pm.h
> +++ b/include/linux/pm.h
> @@ -656,9 +656,11 @@ extern void dpm_for_each_dev(void *data, void (*fn)(struct device *, void *));
>  
>  extern int pm_generic_prepare(struct device *dev);
>  extern int pm_generic_suspend_late(struct device *dev);
> +extern int pm_generic_suspend_late_runtime(struct device *dev);
>  extern int pm_generic_suspend_noirq(struct device *dev);
>  extern int pm_generic_suspend(struct device *dev);
>  extern int pm_generic_resume_early(struct device *dev);
> +extern int pm_generic_resume_early_runtime(struct device *dev);
>  extern int pm_generic_resume_noirq(struct device *dev);
>  extern int pm_generic_resume(struct device *dev);
>  extern int pm_generic_freeze_noirq(struct device *dev);

Thanks!

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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