U-Boot¶

In AM437x the ROM code serves as the 1^st stage bootloader. The 2^nd and the 3^rd stage bootloaders are based on U-Boot.

The binary for the 2^nd stage is referred to as SPL (MLO) and the binary for the 3^rd stage as simply U-Boot. SPL is a non-interactive loader and is a built from the u-boot tree.

The ROM code can load the SPL image from the NAND or SDMMC devices.

Building U-Boot out-of-tree¶

Downloading source code¶

U-Boot sources can be downloaded from https://github.com/varigit/u-boot-VAR-SOM-AMxx.
U-boot is built automatically by bitbake.
This directory already includes Variscite's patches (already applied) to support the VAR-SOM-AM33.

First, clone the git repositories to a local directory, as follows:

$ mkdir ~/varsomam43
$ cd ~/varsomam43
$ git clone https://github.com/varigit/u-boot-VAR-SOM-AMxx.git

Setup Toolchain path¶

$ export PATH=/opt/gcc-linaro-4.9-2015.05-x86_64_arm-linux-gnueabihf/bin/:$PATH

Building U-boot¶

U-boot variant to boot from NAND flash:

$ cd u-boot-VAR-SOM-AMxx
$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- var-som-am43

U-boot variant to boot from SD-Card:

$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- var-som-am43-sd

U-Boot Environment Settings¶

The VAR-SOM-AM43 U-Boot has default environment settings that boot from NAND, SD/MMC card and Ethernet.