Introduction

SBL booting Linux from eMMC (see SBL EMMC Linux Multistage) is a secondary bootloader application that boots Linux on A53 core and RTOS/NORTOS application on R5, M4 cores.
The bootloader makes use of 5 appimages
- A Linux appimage containing the Linux binaries (ATF, OPTEE, A53 SPL).
- tiboot3.bin with SBL stage1, TIFS, BoardConfig
- Appimage for WKUP R5 with SBL stage2
- Appimage for MCU R5
- Appimage for HSM M4
Boots WKUP-R5F, MCU-R5, HSM-M4 cores and Linux on A53 from eMMC.
SBL booting Linux can be used when early booting of WKUP-R5F, HSM-M4 and MCU-R5 cores are required. When using uBoot, the application will start running on WKUP-R5F, HSM-M4 and MCU-R5 cores only after booting Linux.
The Linux appimage can be generated by using Linux Appimage Generator Tool
The appimages will be flashed to the offset on eMMC specified by SysCfg, the SBL parses the appimages from these locations, loads and run the cores.

Bootflow for SBL booting linux from eMMC

Note: The binaries for WKUP-R5F, MCU-R5 cores need not be in the linux root partition (root/lib/firmware), when SBL is booting Linux.

Bootflow for SBL booting Linux

The stage 2 bootloader and the Device manager application are combined as a single appimage
The SBL stage 1 will self load SBL stage 2 + Device manager application to WKUP-R5 core and run self CPU
Then two threads namely, main thread and SBL stage 2 thread will be created for parallel execution
The main thread will open the drivers required for application, do the SciServer init and run the WKUP-R5 core application
The SBL thread will set the clock and open the drivers for the peripherals used by the SBL.
Then it boots the HSM-M4 core, MCU-R5 core and linux on A53 core.

Note: - The peripherals used by SBL and application are separated by using the sysconfig option 'Instance added by bootloader'.; - For the peripherals used by SBL, the 'Instance added by bootloader' option is enabled in the sysconfig as shown.; Instance added by bootloader - sysconfig option; - These peripherals will be opened/closed in the SBL thread and it will not get opened/closed in the common Drivers_open/Drivers_close function called in the main thread.

Note: The default SD card image for AM62Px-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/am62p-mcu-r5f0_0-fw) will not be used when SBL boots Linux and MCU-R5 core.