The CM5 Exaviz system uses a multi-stage boot chain that goes from the Raspberry Pi’s built-in EEPROM through UEFI firmware to GRUB and the Linux kernel.
Boot chain
RPi EEPROM (pieeprom)
└── RPI_EFI.fd (worproject/rpi5-uefi v0.3, on ESP)
└── grubaa64.efi (GRUB arm64-efi, on ESP)
└── linux-rpi (kernel, on /boot)
└── initramfs (dracut, on /boot)
└── Arch Linux rootfs (Btrfs @ subvolume)
ESP contents
The EFI System Partition (ESP, mounted at /boot/efi) contains:
| File | Purpose |
|---|
RPI_EFI.fd | UEFI firmware image |
config.txt | RPi firmware configuration |
EFI/ARCH/grubaa64.efi | GRUB EFI binary |
*.dat, *.elf | RPi firmware support files |
config.txt
The config.txt placed on the ESP by cm5-setup.sh:
# RPi5 / CM5 UEFI config
arm_64bit=1
enable_uart=1
uart_2ndstage=1
# CM5 Exaviz carrier — PCIe/SATA will enumerate after UEFI handoff
dtparam=pciex1=on
# Uncomment if using NVMe on CM5:
# dtparam=nvme=on
gpu_mem=16
| Option | Effect |
|---|
arm_64bit=1 | Boot in 64-bit AArch64 mode |
enable_uart=1 | Enable UART0 (ttyAMA0) for console output |
uart_2ndstage=1 | Keep UART enabled during second-stage bootloader |
dtparam=pciex1=on | Enable the PCIe x1 interface on the CM5 (required for Axelera Metis and SATA) |
dtparam=nvme=on | Enable NVMe on the M.2 slot (commented out — uncomment to activate) |
gpu_mem=16 | Reserve only 16 MB for the GPU (headless server use) |
PCIe and NVMe enumeration happens after the UEFI handoff to GRUB. Devices appear as /dev/nvme0n1 or /dev/sdX once the kernel loads.
grub.cfg written by cm5-setup.sh contains three menu entries:
Primary entry
Fallback entry
UEFI settings
menuentry "Arch Linux RPi5 (btrfs @)" {
linux /boot/Image \
root=UUID=<ROOT_UUID> \
rootfstype=btrfs \
rootflags=subvol=@ \
rw \
rd.luks=0 \
rd.md=0 \
rd.dm=0 \
ip=dhcp \
console=ttyAMA0,115200 \
console=tty1 \
quiet
initrd /boot/initramfs-<KERNEL_VER>.img
}
menuentry "Arch Linux RPi5 - Fallback initrd" {
linux /boot/Image \
root=UUID=<ROOT_UUID> \
rootfstype=btrfs \
rootflags=subvol=@ \
rw \
rd.luks=0 \
ip=dhcp \
console=ttyAMA0,115200 \
console=tty1
initrd /boot/initramfs-<KERNEL_VER>-fallback.img
}
menuentry "UEFI Firmware Settings" {
fwsetup
}
Kernel cmdline parameters explained
| Parameter | Purpose |
|---|
root=UUID=<id> | Root device by UUID (stable across renames) |
rootfstype=btrfs | Filesystem type hint for the kernel |
rootflags=subvol=@ | Mount the @ subvolume as root |
rw | Mount root read-write |
rd.luks=0 | Disable dracut LUKS discovery (no encryption configured) |
rd.md=0 | Disable dracut software RAID |
rd.dm=0 | Disable dracut device-mapper |
ip=dhcp | Configure network via DHCP in initramfs (for early SSH) |
console=ttyAMA0,115200 | UART console at 115200 baud |
console=tty1 | Also output to VGA/HDMI if available |
quiet | Suppress most kernel boot messages (primary entry only) |
Updating the UEFI firmware
Updating pieeprom (RPi EEPROM)
The RPi EEPROM bootloader can be updated from within Arch Linux using rpi-eeprom:
sudo rpi-eeprom-update -a
sudo reboot
rpi-eeprom-update updates pieeprom (the RPi5 EEPROM bootloader), not RPI_EFI.fd. These are separate firmware components.
Updating RPI_EFI.fd (UEFI firmware)
To update the worproject rpi5-uefi firmware, download the new release and replace the file on the ESP manually:
# Download new firmware
wget https://github.com/worproject/rpi5-uefi/releases/download/v0.4/RPi5_UEFI_Firmware_v0.4.zip
# Extract
unzip RPi5_UEFI_Firmware_v0.4.zip -d rpi5-uefi/
# Replace on ESP (ESP is mounted at /boot/efi)
sudo cp rpi5-uefi/RPI_EFI.fd /boot/efi/
sudo cp rpi5-uefi/*.dat /boot/efi/ 2>/dev/null || true
sudo cp rpi5-uefi/*.elf /boot/efi/ 2>/dev/null || true
sudo reboot
Do not remove config.txt from the ESP when updating UEFI firmware — this file is required for the RPi to enter UEFI mode.
