U-Boot

Linux friendly bootloader. Used in various ARM devices like PinePhone and Orange Pi.

Boot process

Definitions

General

• SPL (Secondary Program Loader) is a small binary, generated from U-Boot source, that fits in the SRAM and loads the main U-Boot into system RAM. [1]
• TPL (Tertiary Program Loader) is a tiny SPL which loads moderate-sized middle layer called TPL and that loads the full U-Boot into RAM.

Board-specific

• ATF (ARM Trusted Firmware)

Device Tree

• DTB (Device Tree Blob) TODO: Enhance
• ITB TODO: ???
• FIT (Flat Image Tree) TODO: Enhance

Related

• U-Boot on Allwinner devices
• U-Boot on Orange Pi 4

External

• Presentation of U-Boot and porting to devices [2]
• Get More out of U-Boot (introduction, partitioning, etc.) [3]
• Presentation on TPL: SPL loading SPL (and what is SPL?) [4]