Building a custom firmware for the Banana Pi BPI-F3

Mon, 13 Jan 2025 01:00:00 +0700

I started building the firmware components for booting the BPI-F3 myself. While SpacemiT provides the source code of the different components the official firmware is built from forks of older versions and without the commit history. In my attempt to build a custom firmware I will use mainline versions where possible and otherwise create my own forks from mainline sources and merge necessary changes into it.

Contents:

Status

name	build	test	comment
bootinfo	✅	✅	generated files are identical to vendor files
fsbl	❌	❌	no build yet
opensbi	✅	✅	boot ok (opensbi messages shown in console)
u-boot	✅	❌	doesn’t boot linux and only detects 4GB RAM

Bootinfo

The first part of the boot process we have control of is the bootinfo binary. In the SpacemiT BSP Bianbu Linux the bootinfo is generated by a Python script during the build of u-boot.

With bpif3_gen_binary I extracted and slightly modified this script and according configuration files to be used independent from the u-boot source tree.

The content of the generated bootinfo is specified in a JSON file and could be modified. However, currently I do not see a need for that.

FSBL (U-Boot SPL)

The FSBL (First Stage Boot Loader) is generated by the same script as the bootinfo but requires u-boot-spl.bin at a path specified in the according JSON configuration file.

While mainline u-boot already has support for the BPI-F3, it only generates a u-boot proper stage but not a u-boot spl stage.

OpenSBI

Mainline OpenSBI does not have support for the SpacemiT K1 (yet). Luckily cyyself already merged support for the SoC into a clean fork of OpenSBI.

With bpif3_opensbi I merged his work on to the latest version of mainline OpenSBI.

U-Boot

Mainline u-boot has support for the BPI-F3. It lacks support for the u-boot spl stage but builds the u-boot proper main stage.