usb: core: lpm: add sysfs node for usb3 lpm permit
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: NLu Baolu <baolu.lu@linux.intel.com> Signed-off-by: NZhuang Jin Can <jin.can.zhuang@intel.com> Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
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