Using U-Boot With Linux - Boundary Devices Nitrogen series User Manual

5.2 Das U-Boot
The U-Boot variable bootcmd will be stored in persistent memory
content of this command will be executed if no character is received on the console within a time
frame defined by the bootdelay variable.
Environment variables can be saved using the saveenv command.
U-Boot> set bootcmd 'mmcinit && fatload mmc 0 92000000 NK6.nb0 && go 92000000'
U-Boot> savee
U-Boot> print
In the U-Boot shell, single-quotes do not perform variable expansion of the quoted item, but
double-quotes do.
The print command in U-Boot is used to display the content of all environment variables.
5.2.1

Using U-Boot with Linux

When using U-Boot to load Linux, there are two typical use cases for the bootcmd settings to boot
with or without a RAM-disk. In general, we recommend the use of a RAM-disk whenever booting
to SD card so that the RAM disk, or initrd can perform filesystem checking. The Freescale
Ubuntu image is not currently set up to do so. If you're using an NFS root filesystem, you also
won't want a RAM disk.
Generally, we'll set up bootcmd as follows when using a RAM disk:
U-Boot> set bootcmd 'mmcinit &&
fatload mmc 0 92000000 uImage &&
fatload mmc 0 92400000 &&
bootm 92000000 92400000'
U-Boot> saveenv
In English, this says:
mmcinit - Initialize the SD card
&& - If that works
fatload mmc 0 92000000 uImage - Load uImage from SD card 0 fat filesystem to address
92000000
&& - If that works
fatload mmc 0 92400000 initrd.u-boot - Load RAM-disk (initrd.u-boot) at address
92400000
&& - If that works
bootm 92000000 92400000 - Boot Linux with kernel at 92000000 and initrd at 92400000
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SD card or serial EEPROM
March 10, 2011 Revision 1.5
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and loaded at boot time. The
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