Debugging testusb problems

Hi Aik,

We have a board with two USB ports. One of them is configured as "gadget", the other as host.

In the "other machine" (laptop) test scenario. We connect the board' gadget USB to the USB port of the laptop. The laptop recognizes the USB device. On the laptop, we can execute the `usbtest`. This means that the laptop is performing the test steps. This works fine.

/--------------\                     /-----------\
| Laptop       | host         gadget |     Board |
|              |======= USB =======> |           |
|   $ usbtest  |                     | g_zero    |
\--------------/                     \-----------/

In the "board-only" test scenario. We connect the board' gadget USB to the board' host USB. The logs indicate that the USB device is correctly recognized. But executing `usbtest` on the board, leads to some successful and some failed test steps.

/--------------\
| Board        | gadget
|       g_zero |=====\\
|              |      \\
|              |      || USB
| $ usbtest    |      //
|              |=====//
|              | host
\--------------/

I hope this makes it more clear.

Thomas