[Pandaboard] USB Harddisk not detected by uboot

[Studying]

Problem description:

Booting from SD card on Pandaboard with Latest Arch Linux and then in the U-Boot command prompt executing "usb start" results in no storage devices found. Plugging in an USB thumb-drive however is detected.
$this->bbcode_second_pass_code('', '
U-Boot# usb start
(Re)start USB...
USB0: USB EHCI 1.00
scanning bus 0 for devices... 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#
')
Booting rootfs fromthe SD card partiion the USB drive can be seen (e.g use "blkid") and device as /dev/sda and can be mounted. The hardisk uses a USB to SATA interface was used before on the PB with Ubuntu Linux 12.10 for ARM. teste with 2 different 2.5" SATA drives with the same result.
$this->bbcode_second_pass_code('', '
[root@alarm ~]# blkid
/dev/mmcblk0p1: SEC_TYPE="msdos" LABEL="boot" UUID="A3E1-EE61" TYPE="vfat"
/dev/mmcblk0p2: LABEL="ALARM" UUID="1aad41bf-299c-41a4-b592-000f409e21fa" TYPE="ext4"
/dev/sda2: LABEL="rootfs" UUID="b57f55d9-8128-47e0-9ac2-9990d66056b0" TYPE="ext4"
/dev/mmcblk0: PTTYPE="dos"
')
$this->bbcode_second_pass_code('', '
[root@alarm ~]# mount /dev/sda2 /media/sda2
[root@alarm ~]# cd /media/sda2
[root@alarm sda2]# ls
bin dev home lost+found opt root sbin sys usr
boot etc lib mnt proc run srv tmp var
')
Obeservations: When executing "USB start" the HDD is powered down. The LED on the USB/SATA interface also turns off. After this the drive spins up. Potentially uboot does not give the drive enough time to spin up and to identify itself?

Requirement: I wish to use the rootfs from the USB drive. So this is an issue I hope can be resolved.

Others: There is a similar issues reported in this forum: https://community.freescale.com/thread/327088