USB: Export suspend statistics

This patch exports two statistics to userspace:
/sys/bus/usb/device/.../power/connected_duration
/sys/bus/usb/device/.../power/active_duration

connected_duration is the total time (in msec) that the device has
been connected.  active_duration is the total time the device has not
been suspended.  With these two statistics, tools like PowerTOP can
calculate the percentage time that a device is active, i.e. not
suspended or auto-suspended.

Users can also use the active_duration to check if a device is actually
autosuspended.  Currently, they can set power/level to auto and
power/autosuspend to a positive timeout, but there's no way to know from
userspace if a device was actually autosuspended without looking at the
dmesg output.  These statistics will be useful in creating an automated
userspace script to test autosuspend for USB devices.

Signed-off-by: Sarah Sharp <sarah.a.sharp@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
index bc5edacb0c3..fdb444d8127 100644
--- a/drivers/usb/core/usb.c
+++ b/drivers/usb/core/usb.c
@@ -339,6 +339,8 @@ usb_alloc_dev(struct usb_device *parent, struct usb_bus *bus, unsigned port1)
         mutex_init(&dev->pm_mutex);
         INIT_DELAYED_WORK(&dev->autosuspend, usb_autosuspend_work);
         dev->autosuspend_delay = usb_autosuspend_delay * HZ;
+        dev->connect_time = jiffies;
+        dev->active_duration = -jiffies;
 #endif
         if (root_hub)   /* Root hub always ok [and always wired] */
                 dev->authorized = 1;