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authorKevin Strasser <kevin.strasser@linux.intel.com>2015-06-16 20:35:30 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2015-07-23 01:45:03 +0300
commit655fe4effe0f1f40e4f6ca6b3cc64a7fe0032183 (patch)
tree00e7be3af68a08b25e6688fc8d4571124b81d704 /Documentation/usb/power-management.txt
parenteb4861c3cef7f745df0d2a26b0f4287da0190424 (diff)
downloadlinux-655fe4effe0f1f40e4f6ca6b3cc64a7fe0032183.tar.xz
usbcore: add sysfs support to xHCI usb3 hardware LPM
Add a sysfs node to make it easier to verify if LPM is supported and being enabled for USB 3.0 devices. Signed-off-by: Kevin Strasser <kevin.strasser@linux.intel.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'Documentation/usb/power-management.txt')
-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
----------------------