PM: Introduce core framework for run-time PM of I/O devices (rev. 17)

Introduce a core framework for run-time power management of I/O
devices.  Add device run-time PM fields to 'struct dev_pm_info'
and device run-time PM callbacks to 'struct dev_pm_ops'.  Introduce
a run-time PM workqueue and define some device run-time PM helper
functions at the core level.  Document all these things.

Special thanks to Alan Stern for his help with the design and
multiple detailed reviews of the pereceding versions of this patch
and to Magnus Damm for testing feedback.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Magnus Damm <damm@igel.co.jp>

1 files changed, 98 insertions, 3 deletions

diff --git a/include/linux/pm.h b/include/linux/pm.h
index b3f74764a586..2b6e20df0e52 100644
--- a/include/linux/pm.h
+++ b/include/linux/pm.h
@@ -22,6 +22,10 @@
 #define _LINUX_PM_H
 
 #include <linux/list.h>
+#include <linux/workqueue.h>
+#include <linux/spinlock.h>
+#include <linux/wait.h>
+#include <linux/timer.h>
 
 /*
  * Callbacks for platform drivers to implement.
@@ -165,6 +169,28 @@ typedef struct pm_message {
  * It is allowed to unregister devices while the above callbacks are being
  * executed.  However, it is not allowed to unregister a device from within any
  * of its own callbacks.
+ *
+ * There also are the following callbacks related to run-time power management
+ * of devices:
+ *
+ * @runtime_suspend: Prepare the device for a condition in which it won't be
+ *      able to communicate with the CPU(s) and RAM due to power management.
+ *      This need not mean that the device should be put into a low power state.
+ *      For example, if the device is behind a link which is about to be turned
+ *      off, the device may remain at full power.  If the device does go to low
+ *      power and if device_may_wakeup(dev) is true, remote wake-up (i.e., a
+ *      hardware mechanism allowing the device to request a change of its power
+ *      state, such as PCI PME) should be enabled for it.
+ *
+ * @runtime_resume: Put the device into the fully active state in response to a
+ *      wake-up event generated by hardware or at the request of software.  If
+ *      necessary, put the device into the full power state and restore its
+ *      registers, so that it is fully operational.
+ *
+ * @runtime_idle: Device appears to be inactive and it might be put into a low
+ *      power state if all of the necessary conditions are satisfied.  Check
+ *      these conditions and handle the device as appropriate, possibly queueing
+ *      a suspend request for it.  The return value is ignored by the PM core.
  */
 
 struct dev_pm_ops {
@@ -182,6 +208,9 @@ struct dev_pm_ops {
         int (*thaw_noirq)(struct device *dev);
         int (*poweroff_noirq)(struct device *dev);
         int (*restore_noirq)(struct device *dev);
+        int (*runtime_suspend)(struct device *dev);
+        int (*runtime_resume)(struct device *dev);
+        int (*runtime_idle)(struct device *dev);
 };
 
 /**
@@ -315,14 +344,80 @@ enum dpm_state {
         DPM_OFF_IRQ,
 };
 
+/**
+ * Device run-time power management status.
+ *
+ * These status labels are used internally by the PM core to indicate the
+ * current status of a device with respect to the PM core operations.  They do
+ * not reflect the actual power state of the device or its status as seen by the
+ * driver.
+ *
+ * RPM_ACTIVE           Device is fully operational.  Indicates that the device
+ *                      bus type's ->runtime_resume() callback has completed
+ *                      successfully.
+ *
+ * RPM_SUSPENDED        Device bus type's ->runtime_suspend() callback has
+ *                      completed successfully.  The device is regarded as
+ *                      suspended.
+ *
+ * RPM_RESUMING         Device bus type's ->runtime_resume() callback is being
+ *                      executed.
+ *
+ * RPM_SUSPENDING       Device bus type's ->runtime_suspend() callback is being
+ *                      executed.
+ */
+
+enum rpm_status {
+        RPM_ACTIVE = 0,
+        RPM_RESUMING,
+        RPM_SUSPENDED,
+        RPM_SUSPENDING,
+};
+
+/**
+ * Device run-time power management request types.
+ *
+ * RPM_REQ_NONE         Do nothing.
+ *
+ * RPM_REQ_IDLE         Run the device bus type's ->runtime_idle() callback
+ *
+ * RPM_REQ_SUSPEND      Run the device bus type's ->runtime_suspend() callback
+ *
+ * RPM_REQ_RESUME       Run the device bus type's ->runtime_resume() callback
+ */
+
+enum rpm_request {
+        RPM_REQ_NONE = 0,
+        RPM_REQ_IDLE,
+        RPM_REQ_SUSPEND,
+        RPM_REQ_RESUME,
+};
+
 struct dev_pm_info {
         pm_message_t            power_state;
-        unsigned                can_wakeup:1;
-        unsigned                should_wakeup:1;
+        unsigned int            can_wakeup:1;
+        unsigned int            should_wakeup:1;
         enum dpm_state          status;         /* Owned by the PM core */
-#ifdef  CONFIG_PM_SLEEP
+#ifdef CONFIG_PM_SLEEP
         struct list_head        entry;
 #endif
+#ifdef CONFIG_PM_RUNTIME
+        struct timer_list       suspend_timer;
+        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;
+        unsigned int            ignore_children:1;
+        unsigned int            idle_notification:1;
+        unsigned int            request_pending:1;
+        unsigned int            deferred_resume:1;
+        enum rpm_request        request;
+        enum rpm_status         runtime_status;
+        int                     runtime_error;
+#endif
 };
 
 /*