9.2. Understanding bootloaders in Processor SDK J722S (RTOS/Linux)¶

9.2.1. Introduction¶

There are two bootloaders in Processor SDK J722S (RTOS/Linux). They are:

RTOS Bootloader

Linux Bootloader

This developer note describes about these two bootloaders.

Please reference the MCU+ documentation for more details on the RTOS Bootloader

Linux bootloader uses SPL and uboot to boot various CPUs.

This is included in Processor SDK Linux at below path
```
board-support/ti-u-boot-<version and git tag>
```
This is used when Linux runs on the A53. Most SDK demos like deep learning demos use Linux on the the A53 hence this bootloader is used in many out of box demos.
In this case one would see below files in the SD card

tiboot3.bin - this is the SPL (not SBL) which the ROM bootloader will boot on MCU R5F Core0
tiboot3.bin will boot tifs.bin - this is the SMS firmware binary
tiboot3.bin will boot tispl.bin on the A53 - this is the 1st stage bootloader on the A53 before uboot
tispl.bin on the A53 will boot uboot.img on A72 - this is uboot which will boot Linux
uboot.img will boot non the |arm_core|(such as C7x, R5F) binaries located at below path in rootfs partition of the SD card
```
/lib/firmware/<soc>-<cpu>-fw
```
uboot.img will read a file uEnv.txt which will tell which .dtbo files to apply in addition to below dtb file present in rootfs partition
```
/boot/k3-<soc>-proc-board-tps65917.dtb
```
uboot.img will boot Linux kernel stored in rootfs partition below
```
/boot/Image
```
Linux will use information in the loaded .dtb/dtbo files to configure itself during boot

Note

Vision Apps supports both Linux and QNX running on the A53. (For more information, see LINK).

Both of these HLOS’s are validated using U-boot SPL out of box as default.

This section is not applicable to J722S