SDAA437 July   2026 TDA4VE-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1 Introduction
    1. 1.1 Motivation
    2. 1.2 Scope
    3. 1.3 Target Boot Architecture
  5. 2 Background
    1. 2.1 J721S2 Boot Flow
    2. 2.2 OSPI NOR Flash Overview
    3. 2.3 UBI and UBIFS Overview
  6. 3 OSPI Flash Layout
    1. 3.1 Partition Layout
    2. 3.2 Bootloader Partitions
    3. 3.3 Root Filesystem Partition
  7. 4 Flashing Boot Components
    1. 4.1 Boot Components Overview
    2. 4.2 Identifying OSPI MTD Partitions
    3. 4.3 Flashing Boot Components into OSPI NOR Flash
    4. 4.4 Verifying Boot Components
  8. 5 Creating a UBIFS Root Filesystem
    1. 5.1 Preparing the RootFS Partition
    2. 5.2 Creating a UBI Device
    3. 5.3 Creating a UBIFS Volume
    4. 5.4 Verifying UBIFS Operation
  9. 6 Storing Linux Boot Artifacts in UBIFS
    1. 6.1 Mounting the UBIFS Root Filesystem Volume
    2. 6.2 Creating the Root Filesystem Structure with BusyBox
    3. 6.3 Verifying BusyBox Execution
    4. 6.4 Creating BusyBox Command Links
    5. 6.5 Creating the init Script
    6. 6.6 Testing the Root Filesystem Using chroot
    7. 6.7 Copying the Linux Kernel Image and DTB
  10. 7 Configuring Linux Boot from UBIFS
    1. 7.1 Configuring Boot Arguments
    2. 7.2 Loading the Kernel and DTB from UBIFS
    3. 7.3 Testing Linux Boot
    4. 7.4 Creating a Reusable Boot Command
  11. 8 Booting Linux Entirely from OSPI NOR Flash
    1. 8.1 Automating the Boot Sequence in U-Boot
    2. 8.2 End-to-End Boot Flow
  12. 9 Summary
  13. 10References

3.3 Root Filesystem Partition

The ospi.rootfs partition is used to store all Linux-related software components required for system boot.

Unlike a conventional J721S2 Linux system that stores the kernel image, DTB, and root filesystem on eMMC, this implementation stores all Linux artifacts within a UBIFS volume located in OSPI NOR flash.

Root Filesystem Structure Figure 3-2 Root Filesystem Structure

The partition is formatted as a UBI device and contains a UBIFS volume named rootfs. The volume stores below items.

  • Linux kernel image (Image)
  • Device tree blob (*.dtb)
  • Linux root filesystem
  • Startup scripts and runtime libraries

Both U-Boot and Linux access this same UBIFS volume during the boot process. U-Boot loads the kernel image and DTB from the volume, while Linux subsequently mounts the volume as its root filesystem.

At the completion of the implementation described in this application note, the OSPI NOR flash contains all software components required for Linux boot.

  • tiboot3.bin
  • tispl.bin
  • U-Boot
  • Linux kernel image
  • Device tree blob (DTB)
  • Linux root filesystem

This architecture enables Linux boot without any dependency on SD/eMMC storage.