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, 30 insertions, 0 deletions

diff --git a/drivers/base/power/sysfs.c b/drivers/base/power/sysfs.c
index 1eca50c8e7ca..e56b4388fe61 100644
--- a/drivers/base/power/sysfs.c
+++ b/drivers/base/power/sysfs.c
@@ -6,6 +6,7 @@
 #include <linux/string.h>
 #include <linux/pm_runtime.h>
 #include <asm/atomic.h>
+#include <linux/jiffies.h>
 #include "power.h"
 
 /*
@@ -111,6 +112,33 @@ static ssize_t control_store(struct device * dev, struct device_attribute *attr,
 
 static DEVICE_ATTR(control, 0644, control_show, control_store);
 
+static ssize_t rtpm_active_time_show(struct device *dev,
+                                struct device_attribute *attr, char *buf)
+{
+        int ret;
+        spin_lock_irq(&dev->power.lock);
+        update_pm_runtime_accounting(dev);
+        ret = sprintf(buf, "%i\n", jiffies_to_msecs(dev->power.active_jiffies));
+        spin_unlock_irq(&dev->power.lock);
+        return ret;
+}
+
+static DEVICE_ATTR(runtime_active_time, 0444, rtpm_active_time_show, NULL);
+
+static ssize_t rtpm_suspended_time_show(struct device *dev,
+                                struct device_attribute *attr, char *buf)
+{
+        int ret;
+        spin_lock_irq(&dev->power.lock);
+        update_pm_runtime_accounting(dev);
+        ret = sprintf(buf, "%i\n",
+                jiffies_to_msecs(dev->power.suspended_jiffies));
+        spin_unlock_irq(&dev->power.lock);
+        return ret;
+}
+
+static DEVICE_ATTR(runtime_suspended_time, 0444, rtpm_suspended_time_show, NULL);
+
 static ssize_t rtpm_status_show(struct device *dev,
                                 struct device_attribute *attr, char *buf)
 {
@@ -254,6 +282,8 @@ 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