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CP6940 User Guide
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4.3.2
Bootloader Shell Options
The boot process can be interrupted by entering the bootstopkey phrase “stop”. This will open a bootloader shell session.
Entering "?" provides a list of possible built-in commands, "printenv" provides a list of current environment settings. The
bootloader shell allows to customize boot options and system startup by changing some of its environment variables. A
list of available environment variables and its description can be seen in the table below..
There are three different types of bootloader environment variables:
•
Script: The variable is a set of consecutive (more simple) bootloader commands to perform a specific task. A boot-
loader environment script is executed using the ‘run <script>’ syntax.
•
Var: The variable controls a specific behaviour of the bootloader startup sequence. E.g. the ‘bootdelay’ variable con-
trols 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.
It is possible to modify environment variables and start the pre-defined scripts form the bootloader shell. It is strongly
discouraged to modify the pre-defined script variables. However, definition and execution of user-defined script vari-
ables can be done.
Table 14: Bootloader Environment Variables
Name
Type
Description
baudrate
Var
Serial line baudrate
default: 115200
bootargs
Var
Default kernel arguments. (quiet postresult=0x${postresult}
${vram_kinfo})
bootcmd
Script
This variable defines a command string that is automatically
executed when the initial countdown is not interrupted.
This command is only executed when the variable bootdelay
is also defined!
bootdelay
Var
After reset, U-Boot will wait this number of seconds before it
executes the contents of the bootcmd variable. During this
time a countdown is printed, which can be interrupted by
pressing any key.
Set this variable to 0 boots without delay. Be careful: depend-
ing on the contents of your bootcmd variable, this can prevent
you from entering interactive commands again forever!
Set this variable to -1 to disable autoboot.
default: 3 for boot monitor, 10 for boot write-protected boot
firmware.
bootstopkey
Var
Defines the key phrase that the user needs to type to drop
into the bootloader command line interface during startup.
not set – use string “stop” as bootstop key phrase (default)
<any> - use string <any> as bootstop key phrase
ethaddr
Auto
contains the default base MAC address of the board which is
read from VPD area. If ethaddr environment variable is
changed and stored using 'saveenv', this value will override
VPD setting after board restart.
loadaddr
Var
Default load address for network transfers. This is used as a
temporary storage for netbooting and firmware updates.
default: 0x20000000
setbootargs
Script
This command is used before execution of the boot command
to setup kernel command line properly with current post-
result and vram_kinfo values
