[U-Boot] USB storage with u-boot on RPi B

[Quentin Barbe]

Hello,

I am trying to use u-boot on my raspberry pi model B to boot Linux from 
a usb drive. I followed instructions from http://elinux.org/RPi_U-Boot 
with the mainline git master branch since going through the commit log 
quickly it seems that usb support was added. Unfortunatly it seems that 
my usb drive is not detected by uboot.
Here is the error I get:
usb_new_device: Cannot read configuration, skipping device 058f:6387

Full log:
============================
U-Boot 2015.07-rc1-00148-g4588d61 (May 16 2015 - 18:11:32)

DRAM:  384 MiB
WARNING: Caches not enabled
RPI Model B rev2
MMC:   bcm2835_sdhci: 0
reading uboot.env

** Unable to read "uboot.env" from mmc0:1 **
Using default environment

In:    serial
Out:   lcd
Err:   lcd
Net:   Net Initialization Skipped
No ethernet found.
Hit any key to stop autoboot:  0
U-Boot> usb start
starting USB...
USB0:   Core Release: 2.80a
scanning bus 0 for devices... usb_new_device: Cannot read configuration, 
skipping device 058f:6387
3 USB Device(s) found
        scanning usb for storage devices... 0 Storage Device(s) found
        scanning usb for ethernet devices... 1 Ethernet Device(s) found
U-Boot> usb storage
No storage devices, perhaps not 'usb start'ed..?
U-Boot> usb tree
USB device tree:
   1  Hub (480 Mb/s, 0mA)
   |   U-Boot Root Hub
   |
   +-2  Hub (480 Mb/s, 2mA)
     |
     +-3  Vendor specific (480 Mb/s, 2mA)

U-Boot>
============================

So usb must be somewhat working since the ethernet port seems to be 
detected, but not the drive. Am I missing some configuration or is usb 
storage for rpi just not available yet?

Thanks

--
Quentin