7.36. Raspberry Pi 5

The Raspberry Pi 5 is a single-board computer that contains four Arm Cortex-A76 cores.

This port is a minimal BL31 implementation capable of booting 64-bit EL2 payloads such as Linux and EDK2.

IMPORTANT NOTE: This port isn’t secure. All of the memory used is DRAM, which is available from both the Non-secure and Secure worlds. The SoC does not seem to feature a secure memory controller of any kind, so portions of DRAM can’t be protected properly from the Non-secure world.

7.36.1. Build

To build this platform, run:

CROSS_COMPILE=aarch64-linux-gnu- make PLAT=rpi5 DEBUG=1

The firmware will be generated at build/rpi5/debug/bl31.bin.

The following build options are supported:

  • RPI3_DIRECT_LINUX_BOOT: Enabled by default. Allows direct boot of the Linux kernel from the firmware.

  • PRELOADED_BL33_BASE: Used to specify the fixed address of a BL33 binary that has been preloaded by earlier boot stages (VPU). Useful for bundling BL31 and BL33 in the same armstub image (e.g. TF-A + EDK2).

  • RPI3_PRELOADED_DTB_BASE: This option allows to specify the fixed address of a DTB in memory. Can only be used if device_tree_address= is present in config.txt.

  • RPI3_RUNTIME_UART: Indicates whether TF-A should use the debug UART for runtime messages or not. -1 (default) disables the option, any other value enables it.

7.36.2. Usage

Copy the firmware binary to the first FAT32 partition of a supported boot media (SD, USB) and append armstub=bl31.bin to config.txt, or just rename the file to armstub8-2712.bin.

No other config options or files are required by the firmware alone, this will depend on the payload you intend to run.

For Linux, you must also place an appropriate DTB and kernel in the boot partition. This has been validated with a copy of Raspberry Pi OS.

The VPU will preload a BL33 AArch64 image named either kernel_2712.img or kernel8.img, which can be overridden by adding a kernel=filename option to config.txt.

Kernel and DTB load addresses are also chosen by the VPU and can be changed with kernel_address= and device_tree_address= in config.txt. If TF-A was built with PRELOADED_BL33_BASE or RPI3_PRELOADED_DTB_BASE, setting those config options may be necessary.

By default, all boot stages print messages to the dedicated UART debug port. Configuration is 115200 8n1.

7.36.3. Design

This port is largely based on the RPi 4 one.

The boot process is essentially the same, the only notable difference being that all VPU blobs have been moved into EEPROM (former start4.elf & fixup4.dat). There’s also a custom BL31 TF-A armstub included for PSCI, which can be replaced with this port.