3.10. ARM Trusted Firmware-A

Overview

Trusted Firmware-A (TF-A) provides a reference implementation of secure world software for Armv7-A and Armv8-A, including a Secure Monitor executing at Exception Level 3 (EL3).

ATF is used as the initial start code on ARMv8-A cores for all K3 platforms. After setting up the initial core state and applying any needed errata fixes it sets up itself as the EL3 monitor handler. Following that, it installs the secure world software (OP-TEE) and passes execution on to either the Linux kernel or U-Boot in the non-secure world.

Getting the ATF Source Code

The pre-built TF-A binary should be packaged in TI Processor SDK: <path-to-processor-sdk>/board-support/prebuilt-images/<optional-build-machine-name>/bl31.bin. Use this binary since it has been tested with TI Processor SDK.

If it is not possible to use pre-build binary, use the following:

$ git clone https://git.trustedfirmware.org/TF-A/trusted-firmware-a.git
$ git checkout <hash>

Where <hash> is the commit shown here: TF-A.

Setting up the toolchain paths

Before compiling any of the sources referenced in this document, set the cross compiler paths to the toolchains packaged in the Processor SDK [Recommended] as shown below. Refer to Yocto-built SDK Toolchains section for more details on usage.

host# export CROSS_COMPILE_64="${SDK_INSTALL_DIR}/linux-devkit/sysroots/x86_64-arago-linux/usr/bin/aarch64-oe-linux/aarch64-oe-linux-"
host# export SYSROOT_64="${SDK_INSTALL_DIR}/linux-devkit/sysroots/aarch64-oe-linux"
host# export CC_64="${CROSS_COMPILE_64}gcc --sysroot=${SYSROOT_64}"
host# export CROSS_COMPILE_32="${SDK_INSTALL_DIR}/k3r5-devkit/sysroots/x86_64-arago-linux/usr/bin/arm-oe-eabi/arm-oe-eabi-"

If the Processor SDK is not installed, the Arm GNU toolchains can be downloaded and setup. Refer to ARM toolchains section for more details on usage.

Building ATF

$ make CROSS_COMPILE="$CROSS_COMPILE_64" ARCH=aarch64 PLAT=k3 TARGET_BOARD=j784s4 SPD=opteed K3_USART=0x8

Default load locations

+---------------------------+------------+
| ATF image                 | 0x70000000 |
+---------------------------+------------+
| OP-TEE image              | 0x9e800000 |
+---------------------------+------------+
| U-Boot/Linux kernel image | 0x80080000 |
+---------------------------+------------+
| DTB                       | 0x82000000 |
+---------------------------+------------+