Update from original Marvell U-Boot to mainline U-Boot:
-------------------------------------------------------

Generate the U-Boot image with these commands:

$ make helios4_defconfig
$ make

The resulting image including the SPL binary with the
full DDR setup is "u-boot-spl.kwb".

Now all you need to do is copy this image on a SD card.
For example with this command:

$ sudo dd if=u-boot-spl.kwb of=/dev/sdX bs=512 seek=1

Please use the correct device node for your setup instead
of "/dev/sdX" here!

Boot selection:
---------------

Before powering up the board, boot selection should be done via the SW1 dip
switch (0: OFF, 1: ON):

 - SPI:     00010
 - SD/eMMC: 00111
 - SATA1:   11100
 - UART:    11110

Boot from UART:
---------------

Connect the on-board micro-USB (CF Pro: CON11, CF Base: CON5)
to your host.

Set the SW1 DIP switches to UART boot (see above).

Run the following command to initiate U-Boot download:

  ./tools/kwboot -p -b u-boot-spl.kwb /dev/ttyUSBX

Use the correct UART device node for /dev/ttyUSBX.

When download finishes start your favorite terminal emulator
on /dev/ttyUSBX.