3.3. Build U-Boot¶

During Linux development, the U-Boot source code may need to be modified and recompiled. For example, U-Boot must be recompiled if:

Enabling features which are disabled in the U-Boot defconfig
Disabling features which are enabled in the U-Boot defconfig
Modifying U-Boot source code to port U-Boot to a custom board

This section explains how to rebuild the U-Boot source code provided in the Processor SDK Linux package on the Development Host.

Once the Processor SDK Linux package is installed, the U-Boot source code is under <SDK_INSTALL_DIR>/board-support/u-boot-<version>/ (referred as UBOOT_DIR/ below). The compile instructions below also use some prebuilt binaries which are provided in the Processor SDK Linux package under <SDK_INSTALL_DIR>/board-support/prebuilt-images/.

As explained in the previous section Linux Boot Flow, there are multiple U-Boot images running on AM64x R5 and ARM64 cores. Therefore, both 32bit and 64bit ARM cross-compile toolchains are required to compile U-Boot. The toolchains are provided in the Processor SDK Linux package.

Note

It is strongly recommended to use the toolchain provided in Processor SDK Linux package that corresponds to the U-Boot release. Using different versions of the toolchains could cause unexpected behavior.

Set Toolchain Path

$ export PATH=$PATH:<SDK_INSTALL_DIR>/linux-devkit/sysroots/x86_64-arago-linux/usr/bin

Compile R5 Image

$ cd <UBOOT_DIR>/
$ export ARCH=arm
$ export CROSS_COMPILE=arm-none-linux-gnueabihf-
$ make am64x_evm_r5_defconfig O=build/r5
$ make O=build/r5
$ cd ../k3-image-gen-<version>/
$ make SOC=am64x SBL=<UBOOT_DIR>/build/r5/spl/u-boot-spl.bin SYSFW_PATH=../prebuilt-images/<TI-SYSFW.bin>

where <TI-SYSFW.bin> is ti-sci-firmware-am64x-gp.bin for AM64x devices.

Note

The directory in parameter O=build/r5 can be changed to a different location.

Compile ARM64 Image

$ cd <UBOOT_DIR>/
$ export ARCH=arm
$ export CROSS_COMPILE=aarch64-none-linux-gnu-
$ make am64x_evm_a53_defconfig O=build/arm64

$ make ATF=$(pwd)/../prebuilt-images/bl31.bin TEE=$(pwd)/../prebuilt-images/bl32.bin O=build/arm64

Note

The directory in parameter O=build/arm64 can be changed to a different location.

Target Images

The steps above will generate the following U-Boot images.

tiboot3.bin
Located under folder <SDK_INSTALL_DIR>/board-support/k3-image-gen-<version>/. This is the first stage of the boot loader running on R5F core.

tispl.bin
Located under folder <UBOOT_DIR>/build/arm64/. This is the first stage of the boot loader running on A53 core.

u-boot.img
Located under folder <UBOOT_DIR>/build/arm64/. This is the second stage of the boot loader running on A53 core.

Update U-Boot on SD Card

After the U-Boot images are generated, they can be copied to an SD card that has already been flashed with a bootable Linux image. The SD card has two partitions, boot and root. The U-Boot images should be copied to the boot partition. Insert the SD card into a card reader and plug the card reader into a Linux PC. Then, copy the U-Boot images to the card. Assuming that the SD card boot partition is mounted to /media/<username>/boot:

$ ls /media/<username>/boot
  tiboot3.bin  tispl.bin  uboot.env  u-boot.img  uEnv.txt  wificfg
$ cd <UBOOT_DIR>
$ sudo cp ../k3-image-gen-<version>/tiboot3.bin /media/<username>/boot/
$ sudo cp build/arm64/tispl.bin /media/<username>/boot/
$ sudo cp build/arm64/u-boot.img /media/<username>/boot/
$ sudo umount /media/<username>/boot

Now insert the SD card into the EVM. The EVM should boot with the updated U-Boot.

	Linux Academy for AM64X