U-boot environment

On the SPI flash U-boot has 2 separate binaries. The u-boot binary itself and U-boot's environment. Our default build has 8KB of environment which can be used for variables and scripts to control booting your operating system. These commands are relevant to manipulating the environment:

# Print all environment variables
env print -a

# Sets the variable bootdelay to 5 seconds
env set bootdelay 5;

# Variables can also contain commands
env set hellocmd 'led red on; echo Hello world; led green on;'

# Execute commands saved in a variable
env run hellocmd;

# Commit env changes to the spi flash
# Otherwise changes are lost
env save

# Restore env to default
env default -a

# Remove a variable
env delete emmcboot

For a production environment the best option for setting depends on the number of units. For a smaller number of units it may be simplest to update any required commands manually. For example, a custom cmdline when booting to eMMC may look like this:

env set bootdelay 0;
env set bootcmd 'load mmc 1:1 ${fdtaddr} /boot/imx6q-ts4900-8390.dtb; load mmc 1:1 ${loadaddr} /boot/uImage; env set bootargs 'console=ttymxc0,115200 debug root=/dev/mmcblk1p1 rootwait rw init=/sbin/init'; bootm ${loadaddr} - ${fdtaddr};'
env save

If you are blasting many boards you can use a script to automate this. There are multiple hooks in our default software image. By default we load and source a script from USB or SD/eMMC if either exist.