On 09/06/16 06:47, Adrian Chadd wrote: > missing some bus > barriers for ARM or something? FYI: Most of the USB control and data memory is coherently allocated and don't need barriers. You can try capturing a trace using usbdump, of the traffic on your device, and see where it hangs: usbdump -i usbusX -f Y -s 65536 --HPS