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usbcore: add sysfs support to xHCI usb3 hardware LPM

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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>
This commit is contained in:
Kevin Strasser
2015-06-16 10:35:30 -07:00
committed by Greg Kroah-Hartman
parent eb4861c3ce
commit 655fe4effe
4 changed files with 62 additions and 2 deletions
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15
Documentation/usb/power-management.txt
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@@ -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
----------------------