Update from original Marvell U-Boot to mainline U-Boot:
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The resulting image including the SPL binary with the
full DDR setup is "u-boot-spl.kwb".

To update the SPI NOR flash, please use the following
command:

=> sf probe;tftpboot 2000000 db-88f6820-gp/u-boot-spl.kwb;\
sf update 2000000 0 60000

Note that the original Marvell U-Boot seems to have
problems with the "sf update" command. This does not
work reliable. So here this command should be used:

=> sf probe;tftpboot 2000000 db-88f6820-gp/u-boot-spl.kwb;\
sf erase 0 60000;sf write 2000000 0 60000