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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
env default [-f] var [...]
env delete [-f] var [...]
env edit name
env exists name
env print [-a | name ...]
env run var [...]
env save
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
baudrate
115200
bootcmd
run module_mmc_boot || run
carrier_sd_boot || run netboot
bootdelay
3
ethprime
FEC0
loadaddr
0x80280000
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.
www.kontron.com
[forcibly] reset default environment
[forcibly] reset variable(s) to their default values
[forcibly] delete variable(s)
edit environment variable
tests for existence of variable
print environment
run commands in an environment variable
save environment
Kontron SMARC-sAMX8 - Rev. 1.2
Description
Serial line baudrate
Try booting (in this order) from module
eMMC, carrier uSD card, network
Wait 3 seconds before executing bootcmd
Use Ethernet port FEC0 as default
Default memory location for OS boot
// 52
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