Basic u-Boot usage
Contents |
Introduction
Your first question may be "What is u-Boot ?". The answer is short : u-Boot is a free software bootloader. Conceptually it has the same function as a desktop computer BIOS : it can launch hardware diagnostics as well as boot a kernel using various methods.
Marvell uses a patched version of u-Boot in the SheevaPlug and therefore, it may not be up to date and not have as many features as the mailine version. U-Boot homepage is located at : http://www.denx.de/wiki/U-Boot.
Working with the environment
The environment refers to the whole of environment variables. Environment variables influence the behaviour of most u-Boot commands.
Printing the environment
The command 'printenv', when used alone, displays all of the environment variables.
You can also use 'printenv toto' to only display the value of 'toto'
Setting an environment variable =
You can use 'set' or 'setenv' to define the value of an environment variable. Typing 'setenv toto 12345' will set the value of 'toto' to '12345' Typing 'setenv toto' will clear the environment variable 'toto' (destroying any existing vaue!)
The dangerous command 'resetenv' clears the environment memory and sets it to default values...
Some useful environment variables
The most important variables to set are :
baudrate=115200 -> transmission speed on JTAG port (terminal) loadaddr=0x02000000 -> RAM address where uImage would be loaded
ipaddr=192.168.0.22 -> Local ip of your plug serverip=192.168.0.102 -> ip address of your tftp server netmask=255.255.255.0 -> mask for your private network
