Updating image u boot
You must be sure that you load and install a functional U-Boot binary, which is always a tricky thing when you develop customisations to U-Boot.If something goes wrong, you can re-install the release U-Boot binary as documented in Installing U-Boot to the STM32F7 Discovery Board.When we restore defaults some variables will become unset, and this can lead to other things not working such as findfdt that rely on these run-time set variables.
With this LCPD release all boards are required to use a device tree to boot.
Installing U-Boot to the STM32F7 Discovery Board explains how to install the U-Boot firmware to the board for the first time.
Having installed U-Boot, U-Boot is immediatelly available on the STM32F7 as a primary firmware monitor.
Everything runs well when Kernels u Image got flashed with u-boot and tftp.
I tried ti update the Kernel from within Kernel-prompt using: Loading from NAND 512Mi B 3,3V 8-bit, offset 0x200000 Image Name: Linux-3.9.0 Image Type: ARM Linux Kernel Image (uncompressed) Data Size: 1897760 Bytes = 1.8 MB Load Address: 20008000 Entry Point: 20008000 NAND read from offset 3c0000 failed 0 ** Read error Wrong Image Format for bootm command ERROR: can't get kernel image!