Commit 7490e442 authored by Alan Stern's avatar Alan Stern Committed by Rafael J. Wysocki
Browse files

PM / Runtime: Add no_callbacks flag 



Some devices, such as USB interfaces, cannot be power-managed
independently of their parents, i.e., they cannot be put in low power
while the parent remains at full power.  This patch (as1425) creates a
new "no_callbacks" flag, which tells the PM core not to invoke the
runtime-PM callback routines for the such devices but instead to
assume that the callbacks always succeed.  In addition, the
non-debugging runtime-PM sysfs attributes for the devices are removed,
since they are pretty much meaningless.

The advantage of this scheme comes not so much from avoiding the
callbacks themselves, but rather from the fact that without the need
for a process context in which to run the callbacks, more work can be
done in interrupt context.

Signed-off-by: default avatarAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: default avatarRafael J. Wysocki <rjw@sisk.pl>
parent 140a6c94

Documentation/power/runtime_pm.txt

+37 −0
Original line number Diff line number Diff line 
Run-time Power Management Framework for I/O Devices



(C) 2009 Rafael J. Wysocki <rjw@sisk.pl>, Novell Inc.

(C) 2010 Alan Stern <stern@rowland.harvard.edu>



1. Introduction
@@ -230,6 +231,11 @@ defined in include/linux/pm.h: 
      interface; it may only be modified with the help of the pm_runtime_allow()

      and pm_runtime_forbid() helper functions



  unsigned int no_callbacks;

    - indicates that the device does not use the run-time PM callbacks (see

      Section 8); it may be modified only by the pm_runtime_no_callbacks()

      helper function



All of the above fields are members of the 'power' member of 'struct device'.



4. Run-time PM Device Helper Functions
@@ -349,6 +355,11 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h: 
      counter (used by the /sys/devices/.../power/control interface to

      effectively prevent the device from being power managed at run time)



  void pm_runtime_no_callbacks(struct device *dev);

    - set the power.no_callbacks flag for the device and remove the run-time

      PM attributes from /sys/devices/.../power (or prevent them from being

      added when the device is registered)



It is safe to execute the following helper functions from interrupt context:



pm_request_idle()
@@ -524,3 +535,29 @@ poweroff and run-time suspend callback, and similarly for system resume, thaw, 
restore, and run-time resume, can achieve this with the help of the

UNIVERSAL_DEV_PM_OPS macro defined in include/linux/pm.h (possibly setting its

last argument to NULL).



8. "No-Callback" Devices



Some "devices" are only logical sub-devices of their parent and cannot be

power-managed on their own.  (The prototype example is a USB interface.  Entire

USB devices can go into low-power mode or send wake-up requests, but neither is

possible for individual interfaces.)  The drivers for these devices have no

need of run-time PM callbacks; if the callbacks did exist, ->runtime_suspend()

and ->runtime_resume() would always return 0 without doing anything else and

->runtime_idle() would always call pm_runtime_suspend().



Subsystems can tell the PM core about these devices by calling

pm_runtime_no_callbacks().  This should be done after the device structure is

initialized and before it is registered (although after device registration is

also okay).  The routine will set the device's power.no_callbacks flag and

prevent the non-debugging run-time PM sysfs attributes from being created.



When power.no_callbacks is set, the PM core will not invoke the

->runtime_idle(), ->runtime_suspend(), or ->runtime_resume() callbacks.

Instead it will assume that suspends and resumes always succeed and that idle

devices should be suspended.



As a consequence, the PM core will never directly inform the device's subsystem

or driver about run-time power changes.  Instead, the driver for the device's

parent must take responsibility for telling the device's driver when the

parent's power state changes.

drivers/base/power/power.h

+1 −0
Original line number Diff line number Diff line
@@ -60,6 +60,7 @@ static inline void device_pm_move_last(struct device *dev) {} 


extern int dpm_sysfs_add(struct device *);

extern void dpm_sysfs_remove(struct device *);

extern void rpm_sysfs_remove(struct device *);



#else /* CONFIG_PM */

drivers/base/power/runtime.c

+53 −1
Original line number Diff line number Diff line
@@ -10,8 +10,10 @@ 
#include <linux/sched.h>

#include <linux/pm_runtime.h>

#include <linux/jiffies.h>

#include "power.h"



static int rpm_resume(struct device *dev, int rpmflags);

static int rpm_suspend(struct device *dev, int rpmflags);



/**

 * update_pm_runtime_accounting - Update the time accounting of power states
@@ -148,6 +150,12 @@ static int rpm_idle(struct device *dev, int rpmflags) 
	/* Pending requests need to be canceled. */

	dev->power.request = RPM_REQ_NONE;



	if (dev->power.no_callbacks) {

		/* Assume ->runtime_idle() callback would have suspended. */

		retval = rpm_suspend(dev, rpmflags);

		goto out;

	}



	/* Carry out an asynchronous or a synchronous idle notification. */

	if (rpmflags & RPM_ASYNC) {

		dev->power.request = RPM_REQ_IDLE;
@@ -254,6 +262,10 @@ static int rpm_suspend(struct device *dev, int rpmflags) 
		goto repeat;

	}



	dev->power.deferred_resume = false;

	if (dev->power.no_callbacks)

		goto no_callback;	/* Assume success. */



	/* Carry out an asynchronous or a synchronous suspend. */

	if (rpmflags & RPM_ASYNC) {

		dev->power.request = RPM_REQ_SUSPEND;
@@ -265,7 +277,6 @@ static int rpm_suspend(struct device *dev, int rpmflags) 
	}



	__update_runtime_status(dev, RPM_SUSPENDING);

	dev->power.deferred_resume = false;



	if (dev->bus && dev->bus->pm && dev->bus->pm->runtime_suspend) {

		spin_unlock_irq(&dev->power.lock);
@@ -305,6 +316,7 @@ static int rpm_suspend(struct device *dev, int rpmflags) 
			pm_runtime_cancel_pending(dev);

		}

	} else {

 no_callback:

		__update_runtime_status(dev, RPM_SUSPENDED);

		pm_runtime_deactivate_timer(dev);
@@ -409,6 +421,23 @@ static int rpm_resume(struct device *dev, int rpmflags) 
		goto repeat;

	}



	/*

	 * See if we can skip waking up the parent.  This is safe only if

	 * power.no_callbacks is set, because otherwise we don't know whether

	 * the resume will actually succeed.

	 */

	if (dev->power.no_callbacks && !parent && dev->parent) {

		spin_lock(&dev->parent->power.lock);

		if (dev->parent->power.disable_depth > 0

		    || dev->parent->power.ignore_children

		    || dev->parent->power.runtime_status == RPM_ACTIVE) {

			atomic_inc(&dev->parent->power.child_count);

			spin_unlock(&dev->parent->power.lock);

			goto no_callback;	/* Assume success. */

		}

		spin_unlock(&dev->parent->power.lock);

	}



	/* Carry out an asynchronous or a synchronous resume. */

	if (rpmflags & RPM_ASYNC) {

		dev->power.request = RPM_REQ_RESUME;
@@ -449,6 +478,9 @@ static int rpm_resume(struct device *dev, int rpmflags) 
		goto repeat;

	}



	if (dev->power.no_callbacks)

		goto no_callback;	/* Assume success. */



	__update_runtime_status(dev, RPM_RESUMING);



	if (dev->bus && dev->bus->pm && dev->bus->pm->runtime_resume) {
@@ -482,6 +514,7 @@ static int rpm_resume(struct device *dev, int rpmflags) 
		__update_runtime_status(dev, RPM_SUSPENDED);

		pm_runtime_cancel_pending(dev);

	} else {

 no_callback:

		__update_runtime_status(dev, RPM_ACTIVE);

		if (parent)

			atomic_inc(&parent->power.child_count);
@@ -954,6 +987,25 @@ void pm_runtime_allow(struct device *dev) 
}

EXPORT_SYMBOL_GPL(pm_runtime_allow);



/**

 * pm_runtime_no_callbacks - Ignore run-time PM callbacks for a device.

 * @dev: Device to handle.

 *

 * Set the power.no_callbacks flag, which tells the PM core that this

 * device is power-managed through its parent and has no run-time PM

 * callbacks of its own.  The run-time sysfs attributes will be removed.

 *

 */

void pm_runtime_no_callbacks(struct device *dev)

{

	spin_lock_irq(&dev->power.lock);

	dev->power.no_callbacks = 1;

	spin_unlock_irq(&dev->power.lock);

	if (device_is_registered(dev))

		rpm_sysfs_remove(dev);

}

EXPORT_SYMBOL_GPL(pm_runtime_no_callbacks);



/**

 * pm_runtime_init - Initialize run-time PM fields in given device object.

 * @dev: Device object to initialize.

drivers/base/power/sysfs.c

+49 −7
Original line number Diff line number Diff line
@@ -81,6 +81,9 @@ 
static const char enabled[] = "enabled";

static const char disabled[] = "disabled";



const char power_group_name[] = "power";

EXPORT_SYMBOL_GPL(power_group_name);



#ifdef CONFIG_PM_RUNTIME

static const char ctrl_auto[] = "auto";

static const char ctrl_on[] = "on";
@@ -390,12 +393,6 @@ static DEVICE_ATTR(async, 0644, async_show, async_store); 
#endif /* CONFIG_PM_ADVANCED_DEBUG */



static struct attribute * power_attrs[] = {

#ifdef CONFIG_PM_RUNTIME

	&dev_attr_control.attr,

	&dev_attr_runtime_status.attr,

	&dev_attr_runtime_suspended_time.attr,

	&dev_attr_runtime_active_time.attr,

#endif

	&dev_attr_wakeup.attr,

#ifdef CONFIG_PM_SLEEP

	&dev_attr_wakeup_count.attr,
@@ -409,6 +406,7 @@ static struct attribute * power_attrs[] = { 
#ifdef CONFIG_PM_ADVANCED_DEBUG

	&dev_attr_async.attr,

#ifdef CONFIG_PM_RUNTIME

	&dev_attr_runtime_status.attr,

	&dev_attr_runtime_usage.attr,

	&dev_attr_runtime_active_kids.attr,

	&dev_attr_runtime_enabled.attr,
@@ -417,10 +415,52 @@ static struct attribute * power_attrs[] = { 
	NULL,

};

static struct attribute_group pm_attr_group = {

	.name	= "power",

	.name	= power_group_name,

	.attrs	= power_attrs,

};



#ifdef CONFIG_PM_RUNTIME



static struct attribute *runtime_attrs[] = {

#ifndef CONFIG_PM_ADVANCED_DEBUG

	&dev_attr_runtime_status.attr,

#endif

	&dev_attr_control.attr,

	&dev_attr_runtime_suspended_time.attr,

	&dev_attr_runtime_active_time.attr,

	NULL,

};

static struct attribute_group pm_runtime_attr_group = {

	.name	= power_group_name,

	.attrs	= runtime_attrs,

};



int dpm_sysfs_add(struct device *dev)

{

	int rc;



	rc = sysfs_create_group(&dev->kobj, &pm_attr_group);

	if (rc == 0 && !dev->power.no_callbacks) {

		rc = sysfs_merge_group(&dev->kobj, &pm_runtime_attr_group);

		if (rc)

			sysfs_remove_group(&dev->kobj, &pm_attr_group);

	}

	return rc;

}



void rpm_sysfs_remove(struct device *dev)

{

	sysfs_unmerge_group(&dev->kobj, &pm_runtime_attr_group);

}



void dpm_sysfs_remove(struct device *dev)

{

	rpm_sysfs_remove(dev);

	sysfs_remove_group(&dev->kobj, &pm_attr_group);

}



#else /* CONFIG_PM_RUNTIME */



int dpm_sysfs_add(struct device * dev)

{

	return sysfs_create_group(&dev->kobj, &pm_attr_group);
@@ -430,3 +470,5 @@ void dpm_sysfs_remove(struct device * dev) 
{

	sysfs_remove_group(&dev->kobj, &pm_attr_group);

}



#endif

include/linux/pm.h

+7 −0
Original line number Diff line number Diff line
@@ -41,6 +41,12 @@ extern void (*pm_power_off_prepare)(void); 


struct device;



#ifdef CONFIG_PM

extern const char power_group_name[];		/* = "power" */

#else

#define power_group_name	NULL

#endif



typedef struct pm_message {

	int event;

} pm_message_t;
@@ -475,6 +481,7 @@ struct dev_pm_info { 
	unsigned int		deferred_resume:1;

	unsigned int		run_wake:1;

	unsigned int		runtime_auto:1;

	unsigned int		no_callbacks:1;

	enum rpm_request	request;

	enum rpm_status		runtime_status;

	int			runtime_error;

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