Kontron AM4211 User Manual
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There are 3 different types of bootloader environment variables:
•
Script: The variable is a set of consecutive (more simple) bootloader commands to perform a specific
task. A command script is invoked using the ‘run <script>’ syntax. E.g. the ‘run nuke_env’
command would erase the bootloader environment sectors causing the bootloader to use its
default environment upon next restart.
•
Var: The variable controls a specific behavior of the bootloader startup sequence. E.g. the
‘bootdelay’ variable controls the time u-boot waits before execution of the bootcmd which
normally loads and starts the Linux kernel.
•
Auto: The variable is automatically set during bootloader startup sequence. E.g. the ‘postresult’
variable stores the result of the POST.
It is possible to modify environment variables and start the pre-defined scripts from the bootloader shell. It
is strongly recommended not to modify the pre-defined script variables. However, definition and execution
of user-defined script variables can be done.
For additional information about u-boot, refer to
Modification of bootloader environment variables is done using the ‘setenv’ and ‘saveenv’ bootloader CLI
commands. In the following example, the new environment script variable ‘bootcmdmyscript’ is defined. In
addition, bootdelay is increased to 10. Finally, all changes are stored into flash environment sector.
Kontron T5519# setenv bootcmdmyscript ‘bootp; tftpboot ${loadaddr} myimg.multi; bootm ${loadaddr}’
Kontron T5519# setenv bootdelay 10
Kontron T5519# saveenv
watchdogos
Var
0 – disable OS load watchdog (default)
15...n – timeout in seconds before load OS watchdog fires
Note: This is the pOSWD watchdog
ignoreposterr
Var
0 – stop boot process if power on self test errors are detected
1 – continue boot in the presence of power on self test errors (default)
postresult
Auto
Contains the power on self tests results:
0 - POST successful (default),
1 - POST failed
memtest
Var
0 = no DRAM test during POST
1 - quick DRAM test (default)
2 - full DRAM test
bootstopkey
Var
string to wait for during startup. If this string is entered, U-Boot will interrupt the
boot process, stop the watchdog and will start its internal command line interface.
default: “stop”
CAUTION
Changing bootloader environment variables must be taken very carefully. It will
change system behavior and can lead to a non-booting system
Name
Type
Description