Kontron SMARC-sAMX8 - Rev. 1.2
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7.5. Bootloader Environment
The bootloader environment is used to control bootloader and OS startup behavior. Environment variables can be used
to control boot timing (e.g. bootdelay), interface properties (e.g. baudrate, ethact) or they define memory locations
where OS images are stored before boot (e.g. loadaddr, fdt_addr). In addition, bootloader shell commands can be
combined to environment scripts.
The bootloader environment is permanently stored in the QSPI flash device at offset 0x400000. During bootloader
operation, the environment is held in RAM memory and can be modified and written back to persistent storage.
Bootloader commands to modify the environment are summed up under the "env" command group:
env default [-f] –a
[forcibly] reset default environment
env default [-f] var [...]
[forcibly] reset variable(s) to their default values
env delete [-f] var [...]
[forcibly] delete variable(s)
env edit name
edit environment variable
env exists name
tests for existence of variable
env print [-a | name ...]
print environment
env run var [...]
run commands in an environment variable
env save
save environment
env set [-f] name [arg ...]
However, the legacy commands for environment handling are still available:
"setenv",
"editenv",
"printenv"
"saveenv".
U-Boot standard environment variables are set up for the SMARC_sAMX8 module as shown below.
Table 13: Standard Environment Variables
Variable
Value
Description
baudrate
115200
Serial line baudrate
bootcmd
run module_mmc_boot || run
carrier_sd_boot || run netboot
Try booting (in this order) from module
eMMC, carrier uSD card, network
bootdelay
3
Wait 3 seconds before executing bootcmd
ethprime
FEC0
Use Ethernet port FEC0 as default
loadaddr
0x80280000
Default memory location for OS boot
A typical user modification would be to set the variable "bootcmd" to change OS boot commands.
7.6. Kontron Bootloader Environment Extensions
To support SMARC_sAMX8 board properly, Kontron adds some environment variables to the standard set of variables
provided by mainline U-Boot. These variables are shown below.
