As we know, the bootloader stores its configuration into an area of the flash called the environment. The environment is basically stored as a sequence of null-terminated strings, with a little header containing a checksum at the beginning. Using the “printenv”, “setenv” and “saveenv” commands in U-Boot, while this environment can easily be manipulated. It is sometimes desirable to be able to generate a binary image of an environment that can be directly flashed next to the bootloader, kernel and root filesystem into the device’s flash memory.

In order to modify the U-Boot environment variables from user space, the program called “mkenvimage” is needed, this program can be generated from the U-Boot sources, follow the instructions in the tools/env/README file.

make env

This will get the program “mkenvimage”, the program is executed in host computer, not the target board. The text file “uboot-env.txt” describing the environment is needed like:

git-bash

bootargs=console=ttyS0,115200 bootcmd=tftp 22000000 Image [...]

Then use mkenvimage as follows:

./mkenvimage -s 0x40000 -o uboot-env.bin uboot-env.txt

The -s option allows to specify the size of the image to create. It must match the size of the flash area reserved for the U-Boot environment.

Before using the new uboot-env.bin, the old bin file should be restored by the following commands:

dd if=/dev/mtd7 of=uboot-env.bin

Then, flashing the new bin file in /dev/mtd7 by the following commands:

 

flash_eraseall /dev/mtd7 flashcp uboot-env.bin /dev/mtd7

Or, the Lauterbach Debugger is also a good tool to flash the Hyper-Flash.