Turn USB power off/on with BeagleBone Black kernel >= 3.8

Question

I need to:

• turn off -> sleep some seconds -> turn on the USB power of beaglebone black

to be able to hardware-reset a device that is connected to USB (Huawei E220 Modem)

Already tried soft-reset (with unbind/bind and with authorize 0/1), but software reset is not enough to make the device to work well again; the device has some weird bug, that is triggered by a long-time usage (after a few days connected).

Many answers were found using /sys/debug/omap_mux, but this device does not exist anymore in new kernels.

Since this question took a pair of days to get a workable answer, I decided to post it here, with the answer, so it may be useful for others.

Gosselin

Answer 1

Thanks to my friend Cleiton Bueno http://cleitonbueno.wordpress.com/ that found this solution for me:

prerequisites:

• apt-get install devmem2

Code that solved the problem:

devmem2 0x47401c60 b 0x00
sleep 1
echo "usb1" > /sys/bus/usb/drivers/usb/unbind
sleep 20
echo "usb1" > /sys/bus/usb/drivers/usb/bind
sleep 1
devmem2 0x47401c60 b 0x01

The "devmem2" command is responsible to direct access GPIO3_13 of the beaglebone, that controls the IC that powers on/off the USB port.

The "unbind/bind" commands are responsible to tell the usb driver to "rescan" the port after the power.

Gosselin

This is incredibly useful, thanks for figuring this out. The order of operations seems critical, and the sequence is not 100% reliable. I've had better luck with the sequence being 'unbind', 'bind', power-off, power-on. In my case it is specifically to reset a usb hub and all down-stream devices. Reliability may be related to the hub itself, not your sequence here. – Berneta

where that address (0x47401c60) comes from? I wanna understand. – Stonework

@DavideBerra Not a complete answer to your question, but I did dig up a bit of info on the magic value 0x47401c60. See what I wrote in the answer on this question: #37086557 – Gablet

This is exactly what I needed! However, devmem2 isn't in apt, so the install command fails. I found this blog post for getting a compiled binary: scivision.co/devmem2-on-the-beaglebone-black – Copestone