PM / Runtime: Add runtime PM statistics (v3)

In order for PowerTOP to be able to report how well the new runtime PM is
working for the various drivers, the kernel needs to export some basic
statistics in sysfs.

This patch adds two sysfs files in the runtime PM domain that expose the
total time a device has been active, and the time a device has been
suspended.

With this PowerTOP can compute the activity percentage

Active %age = 100 * (delta active) / (delta active + delta suspended)

and present the information to the user.

I've written the PowerTOP code (slated for version 1.12) already, and the
output looks like this:

Runtime Device Power Management statistics
Active  Device name
 10.0%	06:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8101E/RTL8102E PCI Express Fast Ethernet controller

[version 2: fix stat update bugs noticed by Alan Stern]
[version 3: rebase to -next and move the sysfs declaration]

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>

1 files changed, 47 insertions, 7 deletions

diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index b0ec0e9..b78c401 100644
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -123,6 +123,45 @@ int pm_runtime_idle(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(pm_runtime_idle);
 
+
+/**
+ * update_pm_runtime_accounting - Update the time accounting of power states
+ * @dev: Device to update the accounting for
+ *
+ * In order to be able to have time accounting of the various power states
+ * (as used by programs such as PowerTOP to show the effectiveness of runtime
+ * PM), we need to track the time spent in each state.
+ * update_pm_runtime_accounting must be called each time before the
+ * runtime_status field is updated, to account the time in the old state
+ * correctly.
+ */
+void update_pm_runtime_accounting(struct device *dev)
+{
+	unsigned long now = jiffies;
+	int delta;
+
+	delta = now - dev->power.accounting_timestamp;
+
+	if (delta < 0)
+		delta = 0;
+
+	dev->power.accounting_timestamp = now;
+
+	if (dev->power.disable_depth > 0)
+		return;
+
+	if (dev->power.runtime_status == RPM_SUSPENDED)
+		dev->power.suspended_jiffies += delta;
+	else
+		dev->power.active_jiffies += delta;
+}
+
+static void __update_runtime_status(struct device *dev, enum rpm_status status)
+{
+	update_pm_runtime_accounting(dev);
+	dev->power.runtime_status = status;
+}
+
 /**
  * __pm_runtime_suspend - Carry out run-time suspend of given device.
  * @dev: Device to suspend.
@@ -197,7 +236,7 @@ int __pm_runtime_suspend(struct device *dev, bool from_wq)
 		goto repeat;
 	}
 
-	dev->power.runtime_status = RPM_SUSPENDING;
+	__update_runtime_status(dev, RPM_SUSPENDING);
 	dev->power.deferred_resume = false;
 
 	if (dev->bus && dev->bus->pm && dev->bus->pm->runtime_suspend) {
@@ -228,7 +267,7 @@ int __pm_runtime_suspend(struct device *dev, bool from_wq)
 	}
 
 	if (retval) {
-		dev->power.runtime_status = RPM_ACTIVE;
+		__update_runtime_status(dev, RPM_ACTIVE);
 		if (retval == -EAGAIN || retval == -EBUSY) {
 			if (dev->power.timer_expires == 0)
 				notify = true;
@@ -237,7 +276,7 @@ int __pm_runtime_suspend(struct device *dev, bool from_wq)
 			pm_runtime_cancel_pending(dev);
 		}
 	} else {
-		dev->power.runtime_status = RPM_SUSPENDED;
+		__update_runtime_status(dev, RPM_SUSPENDED);
 		pm_runtime_deactivate_timer(dev);
 
 		if (dev->parent) {
@@ -381,7 +420,7 @@ int __pm_runtime_resume(struct device *dev, bool from_wq)
 		goto repeat;
 	}
 
-	dev->power.runtime_status = RPM_RESUMING;
+	__update_runtime_status(dev, RPM_RESUMING);
 
 	if (dev->bus && dev->bus->pm && dev->bus->pm->runtime_resume) {
 		spin_unlock_irq(&dev->power.lock);
@@ -411,10 +450,10 @@ int __pm_runtime_resume(struct device *dev, bool from_wq)
 	}
 
 	if (retval) {
-		dev->power.runtime_status = RPM_SUSPENDED;
+		__update_runtime_status(dev, RPM_SUSPENDED);
 		pm_runtime_cancel_pending(dev);
 	} else {
-		dev->power.runtime_status = RPM_ACTIVE;
+		__update_runtime_status(dev, RPM_ACTIVE);
 		if (parent)
 			atomic_inc(&parent->power.child_count);
 	}
@@ -848,7 +887,7 @@ int __pm_runtime_set_status(struct device *dev, unsigned int status)
 	}
 
  out_set:
-	dev->power.runtime_status = status;
+	__update_runtime_status(dev, status);
 	dev->power.runtime_error = 0;
  out:
 	spin_unlock_irqrestore(&dev->power.lock, flags);
@@ -1077,6 +1116,7 @@ void pm_runtime_init(struct device *dev)
 	dev->power.request_pending = false;
 	dev->power.request = RPM_REQ_NONE;
 	dev->power.deferred_resume = false;
+	dev->power.accounting_timestamp = jiffies;
 	INIT_WORK(&dev->power.work, pm_runtime_work);
 
 	dev->power.timer_expires = 0;