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usb: core: lpm: add sysfs node for usb3 lpm permit

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USB3 LPM is default on in Linux kernel if both xHCI host controller
and the USB devices declare to be LPM-capable. Unfortunately, some
devices are known to work well with LPM disabled, but to be broken
if LPM is enabled, although it declares the LPM capability.  Users
won't be able to use this kind of devices, until someone puts them
in the kernel blacklist and gets the kernel upgraded.

This patch adds a sysfs node to permit or forbit USB3 LPM U1 or U2
entry for a port. The settings apply to both before and after device
enumeration. Supported values are "0" - neither u1 nor u2 permitted,
"u1" - only u1 is permitted, "u2" - only u2 is permitted, "u1_u2" -
both u1 and u2 are permitted. With this interface, users can use an
LPM-unfriendly USB device on a released Linux kernel.

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Zhuang Jin Can <jin.can.zhuang@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Lu Baolu
2015-11-14 16:26:33 +08:00
committed by Greg Kroah-Hartman
parent bf5ce5bf3c
commit 513072d90a
4 changed files with 116 additions and 4 deletions
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11
Documentation/ABI/testing/sysfs-bus-usb
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@@ -189,6 +189,17 @@ Description:
The file will read "hotplug", "wired" and "not used" if the
information is available, and "unknown" otherwise.
What: /sys/bus/usb/devices/.../(hub interface)/portX/usb3_lpm_permit
Date: November 2015
Contact: Lu Baolu <baolu.lu@linux.intel.com>
Description:
Some USB3.0 devices are not friendly to USB3 LPM. usb3_lpm_permit
attribute allows enabling/disabling usb3 lpm of a port. It takes
effect both before and after a usb device is enumerated. Supported
values are "0" if both u1 and u2 are NOT permitted, "u1" if only u1
is permitted, "u2" if only u2 is permitted, "u1_u2" if both u1 and
u2 are permitted.
What: /sys/bus/usb/devices/.../power/usb2_lpm_l1_timeout
Date: May 2013
Contact: Mathias Nyman <mathias.nyman@linux.intel.com>