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-rw-r--r--Documentation/usb/power-management.txt15
1 files changed, 13 insertions, 2 deletions
diff --git a/Documentation/usb/power-management.txt b/Documentation/usb/power-management.txt
index b5f83911732a..4a15c90bc11d 100644
--- a/Documentation/usb/power-management.txt
+++ b/Documentation/usb/power-management.txt
@@ -521,10 +521,10 @@ enabling hardware LPM, the host can automatically put the device into
lower power state(L1 for usb2.0 devices, or U1/U2 for usb3.0 devices),
which state device can enter and resume very quickly.
-The user interface for controlling USB2 hardware LPM is located in the
+The user interface for controlling hardware LPM is located in the
power/ subdirectory of each USB device's sysfs directory, that is, in
/sys/bus/usb/devices/.../power/ where "..." is the device's ID. The
-relevant attribute files is usb2_hardware_lpm.
+relevant attribute files are usb2_hardware_lpm and usb3_hardware_lpm.
power/usb2_hardware_lpm
@@ -537,6 +537,17 @@ relevant attribute files is usb2_hardware_lpm.
can write y/Y/1 or n/N/0 to the file to enable/disable
USB2 hardware LPM manually. This is for test purpose mainly.
+ power/usb3_hardware_lpm
+
+ When a USB 3.0 lpm-capable device is plugged in to a
+ xHCI host which supports link PM, it will check if U1
+ and U2 exit latencies have been set in the BOS
+ descriptor; if the check is is passed and the host
+ supports USB3 hardware LPM, USB3 hardware LPM will be
+ enabled for the device and this file will be created.
+ The file holds a string value (enable or disable)
+ indicating whether or not USB3 hardware LPM is
+ enabled for the device.
USB Port Power Control
----------------------