Kontron AM4140 U-Boot Bootloader - Manual (Page 34)

U-Boot Usage AM4140 U-Boot Bootloader
Page 34 ID 1052-0281, Rev. 1.0
P R E L I M I N A R Y
5. Environment
The environment is stored in the same flash as U-Boot, usually in the last sector. This provides
the possibility to update U-Boot without changing the environment. The environment can be
modified by the user with the typical commands of the “env” command group: “setenv”,
“editenv”, “printenv” and “saveenv”.
Furthermore, if a larger number of boards require updating, the environment can be updated
by a script, loaded from the SD card, onboard NAND flash, or a network.
A typical user modification would be to set the variable “bootcmd” so that the user’s OS will boot
automatically.
6. Working with U-Boot
6.1 General Operation
Most operations are carried out using the main memory as an intermediate step. It is not pos-
sible, for example, to boot a kernel image directly from a tftp server. Instead, the kernel image
is first loaded to memory and then booted from there with another command.
The same is true when writing new contents to the SPI boot flashes.
This concept is very flexible since it separates the commands which handle the loading of data
from the commands that carry out actions like booting.
6.2 Using the sconf Command
In previous board designs, DIP switches were used to configure the fabric interfaces. In re-
sponse to evolving application requirements, the “sconf” command has been designed to pro-
vide increased configuration flexibility.
The AM4140 is delivered with a default configuration for the external interfaces routed to the
AMC ports. If required, these interfaces may be configured via the “sconf” command according
to the application requirements.
The factory default configuration for the AM4140 is as follows:
• “sconf” base configuration: 0
• SRIO system size: small
• SRIO interface mode: agent
• GbE (AMC port 1): rear
To obtain information about the currently active configuration, invoke the “sconf info” command.