usb: add usb2 Link PM variables to sysfs and usb_device

Adds abitilty to tune L1 timeout (inactivity timer for usb2 link sleep)
and BESL (best effort service latency)via sysfs.

This also adds a new usb2_lpm_parameters structure with those variables to
struct usb_device.

Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>

1 files changed, 27 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-bus-usb b/Documentation/ABI/testing/sysfs-bus-usb
index f093e59cbe5f..9759b8c91332 100644
--- a/Documentation/ABI/testing/sysfs-bus-usb
+++ b/Documentation/ABI/testing/sysfs-bus-usb
@@ -236,3 +236,30 @@ Description:
                 This attribute is to expose these information to user space.
                 The file will read "hotplug", "wired" and "not used" if the
                 information is available, and "unknown" otherwise.
+
+What:           /sys/bus/usb/devices/.../power/usb2_lpm_l1_timeout
+Date:           May 2013
+Contact:        Mathias Nyman <mathias.nyman@linux.intel.com>
+Description:
+                USB 2.0 devices may support hardware link power management (LPM)
+                L1 sleep state. The usb2_lpm_l1_timeout attribute allows
+                tuning the timeout for L1 inactivity timer (LPM timer), e.g.
+                needed inactivity time before host requests the device to go to L1 sleep.
+                Useful for power management tuning.
+                Supported values are 0 - 65535 microseconds.
+
+What:           /sys/bus/usb/devices/.../power/usb2_lpm_besl
+Date:           May 2013
+Contact:        Mathias Nyman <mathias.nyman@linux.intel.com>
+Description:
+                USB 2.0 devices that support hardware link power management (LPM)
+                L1 sleep state now use a best effort service latency value (BESL) to
+                indicate the best effort to resumption of service to the device after the
+                initiation of the resume event.
+                If the device does not have a preferred besl value then the host can select
+                one instead. This usb2_lpm_besl attribute allows to tune the host selected besl
+                value in order to tune power saving and service latency.
+
+                Supported values are 0 - 15.
+                More information on how besl values map to microseconds can be found in
+                USB 2.0 ECN Errata for Link Power Management, section 4.10)