[RFC][PATCH 2/7] PM: Framework for representing PM links between devices

["Rafael J. Wysocki" <rjw@sisk.pl>]

The patch below introduces a framework for representing PM
dependencies between devices.

Every such dependency involves two devices, one of which is a "master"
and the second of which is a "slave", meaning that the "slave" have to
be suspended before the "master" and cannot be resumed before it.  In
principle we could give each device two lists of "dependency
objects", one for the dependencies where the device is the "master"
and the other for the dependencies where the device is the "slave".
Then, each "dependency object" can be represented as

struct pm_link {
    struct device *master;
    struct list_head master_hook;
    struct device *slave;
    struct list_head slave_hook;
};

Add some synchronization, helpers for adding / removing "dependency
objects" etc. and it works.  Instead of checking a device's parent,
walk the list of its "masters", instead of walking the list of a
device's children, walk the list of its "slaves".

The PM core creates these objects for parent-child relationships
automatically, they are also created automatically for ACPI devices
and "regular" devices associated with them.  Other ones will have to
be added by platforms / bus types / drivers etc.

---
 drivers/acpi/glue.c          |    3 
 drivers/base/core.c          |    4 
 drivers/base/power/Makefile  |    2 
 drivers/base/power/common.c  |  201 +++++++++++++++++++++++++++++++++++++++++++
 drivers/base/power/main.c    |   28 +----
 drivers/base/power/power.h   |   33 ++++---
 drivers/base/power/runtime.c |    2 
 include/linux/pm.h           |    4 
 include/linux/pm_link.h      |   30 ++++++
 9 files changed, 266 insertions(+), 41 deletions(-)

Index: linux-2.6/include/linux/pm.h
===================================================================
--- linux-2.6.orig/include/linux/pm.h
+++ linux-2.6/include/linux/pm.h
@@ -408,6 +408,9 @@ enum rpm_request {
 };
 
 struct dev_pm_info {
+	spinlock_t		lock;
+	struct list_head	master_links;
+	struct list_head	slave_links;
 	pm_message_t		power_state;
 	unsigned int		can_wakeup:1;
 	unsigned int		should_wakeup:1;
@@ -420,7 +423,6 @@ struct dev_pm_info {
 	unsigned long		timer_expires;
 	struct work_struct	work;
 	wait_queue_head_t	wait_queue;
-	spinlock_t		lock;
 	atomic_t		usage_count;
 	atomic_t		child_count;
 	unsigned int		disable_depth:3;
Index: linux-2.6/drivers/base/power/power.h
===================================================================
--- linux-2.6.orig/drivers/base/power/power.h
+++ linux-2.6/drivers/base/power/power.h
@@ -1,3 +1,7 @@
+extern void device_pm_init(struct device *dev);
+extern void device_pm_add(struct device *dev);
+extern void device_pm_remove(struct device *dev);
+
 #ifdef CONFIG_PM_RUNTIME
 
 extern void pm_runtime_init(struct device *dev);
@@ -23,7 +27,9 @@ static inline struct device *to_device(s
 	return container_of(entry, struct device, power.entry);
 }
 
-extern void device_pm_init(struct device *dev);
+extern void device_pm_sleep_init(struct device *dev);
+extern void device_pm_list_add(struct device *dev);
+extern void device_pm_list_remove(struct device *dev);
 extern void device_pm_add(struct device *);
 extern void device_pm_remove(struct device *);
 extern void device_pm_move_before(struct device *, struct device *);
@@ -32,17 +38,9 @@ extern void device_pm_move_last(struct d
 
 #else /* !CONFIG_PM_SLEEP */
 
-static inline void device_pm_init(struct device *dev)
-{
-	pm_runtime_init(dev);
-}
-
-static inline void device_pm_remove(struct device *dev)
-{
-	pm_runtime_remove(dev);
-}
-
-static inline void device_pm_add(struct device *dev) {}
+static inline void device_pm_sleep_init(struct device *dev) {}
+static inline void device_pm_list_add(struct device *dev) {}
+static inline void device_pm_list_remove(struct device *dev) {}
 static inline void device_pm_move_before(struct device *deva,
 					 struct device *devb) {}
 static inline void device_pm_move_after(struct device *deva,
@@ -60,7 +58,11 @@ static inline void device_pm_move_last(s
 extern int dpm_sysfs_add(struct device *);
 extern void dpm_sysfs_remove(struct device *);
 
-#else /* CONFIG_PM */
+/* drivers/base/power/link.c */
+extern int pm_link_init(void);
+extern void pm_link_remove_all(struct device *dev);
+
+#else /* !CONFIG_PM */
 
 static inline int dpm_sysfs_add(struct device *dev)
 {
@@ -71,4 +73,7 @@ static inline void dpm_sysfs_remove(stru
 {
 }
 
-#endif
+static inline int pm_link_init(void) { return 0; }
+static inline void pm_link_remove_all(struct device *dev) {}
+
+#endif  /* !CONFIG_PM */
Index: linux-2.6/drivers/base/core.c
===================================================================
--- linux-2.6.orig/drivers/base/core.c
+++ linux-2.6/drivers/base/core.c
@@ -1252,9 +1252,13 @@ int __init devices_init(void)
 	sysfs_dev_char_kobj = kobject_create_and_add("char", dev_kobj);
 	if (!sysfs_dev_char_kobj)
 		goto char_kobj_err;
+	if (pm_link_init())
+		goto pm_link_err;
 
 	return 0;
 
+ pm_link_err:
+	kobject_put(sysfs_dev_char_kobj);
  char_kobj_err:
 	kobject_put(sysfs_dev_block_kobj);
  block_kobj_err:
Index: linux-2.6/include/linux/pm_link.h
===================================================================
--- /dev/null
+++ linux-2.6/include/linux/pm_link.h
@@ -0,0 +1,30 @@
+/*
+ * include/linux/pm_link.h - PM links manipulation core.
+ *
+ * Copyright (c) 2009 Rafael J. Wysocki <rjw@sisk.pl>, Novell Inc.
+ *
+ * This file is released under the GPLv2.
+ */
+
+#ifndef _LINUX_PM_LINK_H
+#define _LINUX_PM_LINK_H
+
+#include <linux/list.h>
+
+struct device;
+
+struct pm_link {
+	struct device *master;
+	struct list_head master_hook;
+	struct device *slave;
+	struct list_head slave_hook;
+};
+
+extern int pm_link_add(struct device *slave, struct device *master);
+extern void pm_link_remove(struct device *dev, struct device *master);
+extern int device_for_each_master(struct device *slave, void *data,
+			   int (*fn)(struct device *dev, void *data));
+extern int device_for_each_slave(struct device *master, void *data,
+			  int (*fn)(struct device *dev, void *data));
+
+#endif
Index: linux-2.6/drivers/base/power/Makefile
===================================================================
--- linux-2.6.orig/drivers/base/power/Makefile
+++ linux-2.6/drivers/base/power/Makefile
@@ -1,4 +1,4 @@
-obj-$(CONFIG_PM)	+= sysfs.o
+obj-$(CONFIG_PM)	+= sysfs.o common.o
 obj-$(CONFIG_PM_SLEEP)	+= main.o
 obj-$(CONFIG_PM_RUNTIME)	+= runtime.o
 obj-$(CONFIG_PM_TRACE_RTC)	+= trace.o
Index: linux-2.6/drivers/base/power/runtime.c
===================================================================
--- linux-2.6.orig/drivers/base/power/runtime.c
+++ linux-2.6/drivers/base/power/runtime.c
@@ -972,8 +972,6 @@ EXPORT_SYMBOL_GPL(pm_runtime_enable);
  */
 void pm_runtime_init(struct device *dev)
 {
-	spin_lock_init(&dev->power.lock);
-
 	dev->power.runtime_status = RPM_SUSPENDED;
 	dev->power.idle_notification = false;
 
Index: linux-2.6/drivers/base/power/main.c
===================================================================
--- linux-2.6.orig/drivers/base/power/main.c
+++ linux-2.6/drivers/base/power/main.c
@@ -21,6 +21,7 @@
 #include <linux/kallsyms.h>
 #include <linux/mutex.h>
 #include <linux/pm.h>
+#include <linux/pm_link.h>
 #include <linux/pm_runtime.h>
 #include <linux/resume-trace.h>
 #include <linux/rwsem.h>
@@ -50,17 +51,6 @@ static DEFINE_MUTEX(dpm_list_mtx);
 static bool transition_started;
 
 /**
- * device_pm_init - Initialize the PM-related part of a device object.
- * @dev: Device object being initialized.
- */
-void device_pm_init(struct device *dev)
-{
-	dev->power.status = DPM_ON;
-	spin_lock_init(&dev->power.lock);
-	pm_runtime_init(dev);
-}
-
-/**
  * device_pm_lock - Lock the list of active devices used by the PM core.
  */
 void device_pm_lock(void)
@@ -77,14 +67,11 @@ void device_pm_unlock(void)
 }
 
 /**
- * device_pm_add - Add a device to the PM core's list of active devices.
+ * device_pm_list_add - Add a device to the PM core's list of active devices.
  * @dev: Device to add to the list.
  */
-void device_pm_add(struct device *dev)
+void device_pm_list_add(struct device *dev)
 {
-	pr_debug("PM: Adding info for %s:%s\n",
-		 dev->bus ? dev->bus->name : "No Bus",
-		 kobject_name(&dev->kobj));
 	mutex_lock(&dpm_list_mtx);
 	if (dev->parent) {
 		if (dev->parent->power.status >= DPM_SUSPENDING)
@@ -98,24 +85,19 @@ void device_pm_add(struct device *dev)
 		 */
 		dev_WARN(dev, "Parentless device registered during a PM transaction\n");
 	}
-
 	list_add_tail(&dev->power.entry, &dpm_list);
 	mutex_unlock(&dpm_list_mtx);
 }
 
 /**
- * device_pm_remove - Remove a device from the PM core's list of active devices.
+ * device_pm_list_remove - Remove a device from the PM core's list of devices.
  * @dev: Device to be removed from the list.
  */
-void device_pm_remove(struct device *dev)
+void device_pm_list_remove(struct device *dev)
 {
-	pr_debug("PM: Removing info for %s:%s\n",
-		 dev->bus ? dev->bus->name : "No Bus",
-		 kobject_name(&dev->kobj));
 	mutex_lock(&dpm_list_mtx);
 	list_del_init(&dev->power.entry);
 	mutex_unlock(&dpm_list_mtx);
-	pm_runtime_remove(dev);
 }
 
 /**
Index: linux-2.6/drivers/base/power/common.c
===================================================================
--- /dev/null
+++ linux-2.6/drivers/base/power/common.c
@@ -0,0 +1,201 @@
+/*
+ * drivers/base/power/common.c - device PM common functions.
+ *
+ * Copyright (c) 2009 Rafael J. Wysocki <rjw@sisk.pl>, Novell Inc.
+ *
+ * This file is released under the GPLv2.
+ */
+
+#include <linux/rculist.h>
+#include <linux/device.h>
+#include <linux/srcu.h>
+#include <linux/pm_link.h>
+
+#include "power.h"
+
+/**
+ * device_pm_init - Initialize the PM-related part of a device object
+ * @dev: Device object being initialized.
+ */
+void device_pm_init(struct device *dev)
+{
+	dev->power.status = DPM_ON;
+	spin_lock_init(&dev->power.lock);
+	INIT_LIST_HEAD(&dev->power.master_links);
+	INIT_LIST_HEAD(&dev->power.slave_links);
+	pm_runtime_init(dev);
+}
+
+void device_pm_add(struct device *dev)
+{
+	pr_debug("PM: Adding info for %s:%s\n",
+		 dev->bus ? dev->bus->name : "No Bus",
+		 kobject_name(&dev->kobj));
+	pm_link_add(dev, dev->parent);
+	device_pm_list_add(dev);
+}
+
+void device_pm_remove(struct device *dev)
+{
+	pr_debug("PM: Removing info for %s:%s\n",
+		 dev->bus ? dev->bus->name : "No Bus",
+		 kobject_name(&dev->kobj));
+	device_pm_list_remove(dev);
+	pm_runtime_remove(dev);
+	pm_link_remove_all(dev);
+}
+
+static struct srcu_struct pm_link_ss;
+static DEFINE_MUTEX(pm_link_mtx);
+
+int pm_link_add(struct device *slave, struct device *master)
+{
+	struct pm_link *link;
+	int error = -ENODEV;
+
+	if (!get_device(master))
+		return error;
+
+	if (!get_device(slave))
+		goto err_slave;
+
+	link = kzalloc(sizeof(*link), GFP_KERNEL);
+	if (!link)
+		goto err_link;
+
+	dev_dbg(slave, "PM: Creating PM link to (master) %s %s\n",
+		dev_driver_string(master), dev_name(master));
+
+	link->master = master;
+	INIT_LIST_HEAD(&link->master_hook);
+	link->slave = slave;
+	INIT_LIST_HEAD(&link->slave_hook);
+
+	spin_lock_irq(&master->power.lock);
+	list_add_tail_rcu(&link->master_hook, &master->power.master_links);
+	spin_unlock_irq(&master->power.lock);
+
+	spin_lock_irq(&slave->power.lock);
+	list_add_tail_rcu(&link->slave_hook, &slave->power.slave_links);
+	spin_unlock_irq(&slave->power.lock);
+
+	return 0;
+
+ err_link:
+	error = -ENOMEM;
+	put_device(slave);
+
+ err_slave:
+	put_device(master);
+
+	return error;
+}
+EXPORT_SYMBOL_GPL(pm_link_add);
+
+static void __pm_link_remove(struct pm_link *link)
+{
+	struct device *master = link->master;
+	struct device *slave = link->slave;
+
+	dev_dbg(slave, "PM: Removing PM link to (master) %s %s\n",
+		dev_driver_string(master), dev_name(master));
+
+	spin_lock_irq(&master->power.lock);
+	list_del_rcu(&link->master_hook);
+	spin_unlock_irq(&master->power.lock);
+
+	spin_lock_irq(&slave->power.lock);
+	list_del_rcu(&link->slave_hook);
+	spin_unlock_irq(&slave->power.lock);
+
+	synchronize_srcu(&pm_link_ss);
+
+	kfree(link);
+
+	put_device(master);
+	put_device(slave);
+}
+
+void pm_link_remove_all(struct device *dev)
+{
+	struct pm_link *link, *n;
+
+	mutex_lock(&pm_link_mtx);
+
+	list_for_each_entry_safe(link, n, &dev->power.master_links, master_hook)
+		__pm_link_remove(link);
+
+	list_for_each_entry_safe(link, n, &dev->power.slave_links, slave_hook)
+		__pm_link_remove(link);
+
+	mutex_unlock(&pm_link_mtx);
+}
+
+void pm_link_remove(struct device *dev, struct device *master)
+{
+	struct pm_link *link, *n;
+
+	mutex_lock(&pm_link_mtx);
+
+	list_for_each_entry_safe(link, n, &dev->power.slave_links, slave_hook) {
+		if (link->master != master)
+			continue;
+
+		__pm_link_remove(link);
+		break;
+	}
+
+	mutex_unlock(&pm_link_mtx);
+}
+EXPORT_SYMBOL_GPL(pm_link_remove);
+
+int device_for_each_master(struct device *slave, void *data,
+			   int (*fn)(struct device *dev, void *data))
+{
+	struct pm_link *link;
+	int idx;
+	int error = 0;
+
+	idx = srcu_read_lock(&pm_link_ss);
+
+	list_for_each_entry(link, &slave->power.slave_links, slave_hook) {
+		struct device *master = link->master;
+
+		error = fn(master, data);
+		if (error)
+			break;
+	}
+
+	srcu_read_unlock(&pm_link_ss, idx);
+
+	return error;
+}
+EXPORT_SYMBOL_GPL(device_for_each_master);
+
+int device_for_each_slave(struct device *master, void *data,
+			  int (*fn)(struct device *dev, void *data))
+{
+	struct pm_link *link;
+	int idx;
+	int error = 0;
+
+	idx = srcu_read_lock(&pm_link_ss);
+
+	list_for_each_entry(link, &master->power.master_links, master_hook) {
+		struct device *slave = link->slave;
+
+		error = fn(slave, data);
+		if (error)
+			break;
+	}
+
+	srcu_read_unlock(&pm_link_ss, idx);
+
+	return error;
+}
+EXPORT_SYMBOL_GPL(device_for_each_slave);
+
+int __init pm_link_init(void)
+{
+	return init_srcu_struct(&pm_link_ss);
+}
Index: linux-2.6/drivers/acpi/glue.c
===================================================================
--- linux-2.6.orig/drivers/acpi/glue.c
+++ linux-2.6/drivers/acpi/glue.c
@@ -11,6 +11,7 @@
 #include <linux/device.h>
 #include <linux/rwsem.h>
 #include <linux/acpi.h>
+#include <linux/pm_link.h>
 
 #define ACPI_GLUE_DEBUG	0
 #if ACPI_GLUE_DEBUG
@@ -170,6 +171,7 @@ static int acpi_bind_one(struct device *
 			device_set_wakeup_enable(dev,
 						acpi_dev->wakeup.state.enabled);
 		}
+		pm_link_add(dev, &acpi_dev->dev);
 	}
 
 	return 0;
@@ -189,6 +191,7 @@ static int acpi_unbind_one(struct device
 					&acpi_dev)) {
 			sysfs_remove_link(&dev->kobj, "firmware_node");
 			sysfs_remove_link(&acpi_dev->dev.kobj, "physical_node");
+			pm_link_remove(dev, &acpi_dev->dev);
 		}
 
 		acpi_detach_data(dev->archdata.acpi_handle,