Jetson TX2 Boot Flow

NVIDIA Tegra Linux Driver Package

Development Guide

32.1 Release

BootROM

Bootloader Components

TegraBoot

C-Boot

U-Boot

The flow of control in the boot software is as follows.

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BootROM

The NVIDIA® Jetson™ TX2 BootROM (BR) is hard-wired in the Tegra chip. It initializes the Boot Media and loads Microboot1 (MB1) from the Boot Media.

Multiple copies of the BootROM Boot Configuration Table (BR-BCT) may be stored at the start of the Boot-Media. The BR-BCT contains configuration parameters used by the BootROM for hardware initialization.

The BCT also contains information about the bootloader (BL), including:

• Size

• Entry point

• Load address

• Hash

The BootROM uses this information to verify and load the bootloader. The boot flow is as follows:

$C:\sw\swdocs\mobile\tegra\images\bdk_bootrom_flow.jpg$

Bootloader Components

The Jetson TX2 bootloader and flash components are:

• Common Driver Framework (CDF)

• Microboot1 (MB1)

• TBoot-BPMP (MB2)

• CPU-BL

• TBoot-CPU

• C‑Boot

• U-Boot

Common Driver Framework

MB1, TegraBoot-BPMP, and TegraBoot-CPU/C‑Boot each needs to use one of several drivers. Moreover, some libraries are common across the bootloader components. Instead of using separate sets of drivers and libraries, the binaries share a common pool of drivers and libraries called the Common Driver Framework (CDF).

Note:

Since U-Boot is built separately from the NVIDIA-proprietary bootloader software, it does not support or use CDF.

The software design architecture using the Common Driver Framework is as follows:

Common Driver Framework consists of:

• Storage drivers like eMMC, QSPI, mSATA, and UFS

• Host interface drivers like UART, USB

• Display drivers

• Debug and Console library

• Libraries of other modules such as:

• Clock

• SE

• PMIC

• Timer

• Fuse

• GPIO

• PWM

• EEPROM

• Keyboard

• PSCI

• Software libraries such as:

• Cryptographic

• Transport

• Partition manager

• Sparse

• Transport libraries

• A decompression library that supports LZF, Zlib, and LZ4

• clib, a dynamic memory allocation library, and a cache library

The CDF is provided at:

<top>/vendor/nvidia/tegra/bootloader/partner/common/

<top>/vendor/nvidia/tegra/bootloader/partner/t18x/common/

Microboot1

Jetson TX2 Microboot1 (MB1) is the first boot software component loaded by BR in SysRAM, and runs on BPMP. MB1 is considered as an extension to BR. MB1 provides extensive flexibility to alter or fix the boot sequence. This component also implements some delicate functionality like Denver initialization and security fabric changes.

Because MB1 is an extension to BootROM, it is signed and encrypted by an NVIDIA owned key (separate keys residing in BootROM). The following diagram shows the flow of control in MB1.

$C:\sw\swdocs\mobile\tegra\images\bdk_microboot.jpg$

MB1 is responsible for:

• Firmware initialization, include MTS preboot, SPE, and CAN

• Platform configuration which includes:

• Configuring pinmux

• Configuring GPIO

• Pad settings

• Prod settings

• Initializing rails including those required by CPU, memory, GPU, etc.

• PMIC commands required by BR

• Configuring SCR

• Initialize the SDRAM based on the MB1 boot configuration table (MB1-BCT)

• Load the firmware that initializes the CPU complex (CCplex)

• Set the security settings

• Configure pinmux/GPIO for the SoC

• Program the PMIC for the VDD_CPU and VDD_DDR rails

• Create carveouts

• Support flashing, available as a different mb1_recovery.bin binary

• Support RCM boot by downloading a blob that contains the binaries, and loading binaries from that blob

• Load the next stage bootloader, TBoot-BPMP (MB2)

• Support SC7

MB1 is owned by NVIDIA, and so is provided as a binary in the BSP package. Although it is provided as a binary, you can configure its behavior for a specific platform using its Boot Configuration Table, called MB1-BCT. MB1 reads MB1-BCT to configure the platform.

For information on MB1, see MB1 BCT .

TegraBoot

Jetson TX2 TegraBoot is the bootloader component that executes after MB1. This component is divided into two portions:

• TBoot-BPMP (MB2)

• TBoot-CPU

The processor on which they are executing determines which component runs. Both are released to OEMs as source code for reference implementation.

TegraBoot-BPMP

This portion of Jetson TX2 TegraBoot runs on BPMP (tboot-BPMP). There are two variants of TegraBoot-BPMP (MB2):

• One used for cold boot

• One for recovery boot

Both are generated using different configuration files and make files.

TBoot-BPMP is responsible for:

• Loading and initializing firmware (FW) components

• Creating carveouts

• Completing CPU initialization

• Loading the next stage bootloader

• Supporting flashing

• Supporting RCM boot; which is the TegraBoot-BPMP (MB2) recovery boot

• Reading PMIC reset reason

• Loading the bootloader device tree and passing the device tree load address to CPU-BL

• Giving control to BPMP-FW

The components of TBoot-BPMP are as follows:

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TegraBoot-CPU

Jetson TX2 TegraBoot-CPU is responsible for:

• Flashing

• RCM boot

The flow for RCM boot is similar to a cold boot except that the binaries are transferred from the host over USB and loaded directly to SDRAM. TOS and BPMP-FW are not loaded in this path.

Note:

As soon as the CPU starts running, it starts in EL3 mode. The TOS monitor code completes its initialization and gives control to the TegraBoot-CPU. It then initializes the USB and starts the 3P protocol to flash the device.

• For normal flashing TegraBoot-CPU takes the binaries from the host one-by-one and flashes them to the device.

• In RCM boot, TegraBoot-CPU takes the binaries from the blob downloaded by MB1. The binaries are not flashed onto the device.

TBoot-CPU can also support cold boot by integrating the relevant libraries such as linuxboot, etc. This version of TBoot-CPU is not tested or maintained, though.

The components of TBoot-CPU are as follows:

C-Boot

Jetson TX2 C‑Boot is the primary CPU bootloader used on mobile platforms in the cold boot path. C‑Boot is feature-rich bootloader that:

• Boots the kernel

• Supports display, boot logo, and Verified boot

• Based on the Little Kernel (LK) open source bootloader

• Uses the interrupt and scheduling frameworks of LKC

• Uses CDF for frameworks, drivers, and libraries

Note:

As soon as the CPU starts running, it starts in EL3 mode and begins executing TOS. TOS completes its initialization and passes control to C‑Boot in EL2 mode.

BL and Kernel use separate device trees stored in separate partitions. C‑Boot is responsible for:

• Parsing the CPU-BL parameters and initializing the bootloader device tree

• Booting to the kernel or chaining to U-Boot to boot the kernel

• Supporting the update mechanism

• Loading the recovery kernel

• Verified boot

The components of C‑Boot are as follows:

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The source code for C‑Boot is available to the public at:

https://developer.nvidia.com/embedded/downloads

The source code is in a file named cboot_src.tbz2. It includes instructions for users.

U-Boot

U-Boot is the default bootloader for NVIDIA® Tegra® Linux Driver Package.

For more information, see:

• U-Boot Customization

• TX2 MB1 Platform Configuration