U-Boot

In AM335x the ROM code serves as the 1st stage bootloader. The 2nd and the 3rd stage bootloaders are based on U-Boot.

The binary for the 2nd stage is referred to as SPL (MLO) and the binary for the 3rd 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 git://github.com/varigit/u-boot-VAR-SOM-AM33-SDK7.git.
U-boot is built automatically by bitbake.
This directory already includes Variscite's patches (already applied) to support the VAR-SOM-AM33.
Based on the open source repositorie: https://git.ti.com/ti-u-boot/ti-u-boot/trees/ti-u-boot-2013.01.01-amsdk-06.00.00.00, commit: 540aa6fbb0c9274bda598f7e8819ed28259cad6b.

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

$ mkdir ~/varsomam33
$ cd ~/varsomam33
$ git clone git://github.com/varigit/u-boot-VAR-SOM-AM33-SDK7.git

Setup Toolchain path

$ export PATH=/opt/gcc-linaro-5.3.1-2016.05-x86_64_arm-linux-gnueabihf/bin:$PATH

Building U-boot

U-boot variant to boot from NAND flash:

$ cd u-boot-VAR-SOM-AM33-SDK7
$ git checkout krogoth
$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- var-som-am33

U-boot variant to boot from SD-Card:

$ make ARCH=arm CROSS_COMPILE=arm-linux-gnueabihf- var-som-am33-sd

U-Boot Environment Settings

The VAR-SOM-AM33 U-Boot has default environment settings that boot from NAND, SD/MMC card and Ethernet.

VAR-SOM-AM33 Yocto Krogoth Build u-boot out of tree

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