As noted at the end of answer this is presumably already on. (Also when Q was posted.)
Also note that the cross post was closed due to no answer – thus most appropriate to post here. And I imagine others can have use of the information.
The doc you linked say (emphasize mine):
Note that the "USB-persist" feature will be applied only to those
devices for which it is enabled. You can enable the feature by doing
echo 1 >/sys/bus/usb/devices/.../power/persist
where the "..." should be filled in the with the device's ID. Disable
the feature by writing 0 instead of 1. For hubs the feature is
automatically and permanently enabled and the power/persist file
doesn't even exist, so you only have to worry about setting it for
devices where it really matters.
In other words: (it seems like) you are trying to set it for a hub, which both is redundant – as it is always set, and not possible as file does not exist.
To see which paths actually has a
persist file do:
$ ls -l /sys/bus/usb/devices/*/power/persist
To check status do:
$ tail /sys/bus/usb/devices/*/power/persist
If you use
lsusb to identify device the correct path is
dmesg, etc. e.g.:
$ dmesg | grep -iA3 "new usb"
You can also verify by e.g.:
$ udevadm info -q all -p /sys/bus/usb/devices/<BUS>-<DEVPATH>
The policy for
persist was changed to
on as default by kernel 2.6.26-rc5.
Some ref's on the change to enabled by default: