Introduction

SBL booting Linux (see SBL OSPI Linux) is a secondary bootloader application that boots Linux on A53 core and RTOS/NORTOS application on R5, M4 cores.
The bootloader makes use of two appimages
- One containing the application images(RTOS/NORTOS) for R5, M4 cores
- Other containing the Linux binaries(ATF, OPTEE, SPL) for A53 core.
The Linux appimage can be generated by using Linux Appimage Generator Tool
The appimages will be flashed to the offset specified by SysCfg, the SBL parses the appimages from these locations, loads and run the cores.

Features Supported

Boots R5, M4 cores and Linux on A53 from OSPI.
SBL booting Linux can be used when early booting of R5 and M4 cores are required. When using uBoot to run R5 and M4 cores the application will start running on R5, M4 cores only after booting Linux

SBL booting Linux supports only booting from OSPI and eMMC (see SBL EMMC Linux).
If SD card or other boot modes are required, user might need to switch to booting Linux using Linux uBoot.

Note: The binaries for R5, M4 cores need not be in the linux root partition (root/lib/firmware), when SBL is booting Linux.

Bootflow for SBL booting Linux

Note: The memory load address for core applications must not overlap with one other

Attention: The load address for R5 and M4 core applications must be consistant with the memory layout in Linux dts

SRAM memory map for SBL booting Linux

Note: The flash address R5, M4 appimages and Linux appimages can be configured using Syscfg

OSPI memory map for SBL booting Linux

Note: The default SD card image for AM64x-evm can be used to boot Linux using SBL; The tiboot3.bin, tispl.bin will not be used for booting Linux when using SBL booting Linux.; The R5 binaries in the root partition (eg : root/lib/firmware/am64-main-r5f0_0-fw) will not be used when SBL boots Linux and R5,M4 cores.