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booteeprom.md

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Raspberry Pi 4 boot EEPROM

The Raspberry Pi 4 has an SPI-attached EEPROM (4MBits/512KB), which contains code to boot up the system and replaces bootcode.bin previously found in the boot partition of the SD card. Note that if a bootcode.bin is present in the boot partition of the SD card in a Pi 4, it is ignored.

Why use an SPI EEPROM?

  • Raspberry Pi 4 bootup procedure and SDRAM setup is considerably more complicated than on the previous Raspberry Pi models, so there is more risk inherent in code that's permanently incorporated in the ROM of the SoC.
  • USB has moved to a PCIe bus, and the Gigabit Ethernet driver is completely different to previous models, so again, having it permanently fixed into the ROM of the SoC was not feasible.
  • A small SPI EEPROM allows bugs to be fixed and features to be added after launch, in the field.
  • The local modifiable state means that OTP bootmode settings will not be required for network or USB mass storage boot on the Raspberry Pi 4. There are no user-modifiable OTP bootmode bits on Pi 4.

Network and USB boot

Support for these additional bootmodes will be added in the future via optional bootloader updates. The current schedule is to release network boot first, then USB boot.

Is the bootloader working correctly?

To check that the bootloader is working correctly, turn off the power, unplug everything from the Raspberry Pi 4, including the SD card, and then turn the power back on. If the green LED blinks with a repeating pattern then the bootloader is running correctly, and indicating that start*.elf has not been found. Any other actions imply that the bootloader is not working correctly and should be reinstalled using recovery.bin.

Recovery image

If the Raspberry Pi is not booting it's possible that the bootloader EEPROM is corrupted. This can easily be reprogrammed using the Recovery image available on the raspberrypi.org downloads page.

Updating the bootloader

We recommend setting up your Pi so that it automatically updates the bootloader: this means you will get new features and bug fixes as they are released. Bootloader updates are performed by the rpi-eeprom package, which installs a service that runs at boot-time to check for critical updates.

sudo apt update
sudo apt full-upgrade
sudo apt install rpi-eeprom

If you wish to control when the updates are applied you can disable the systemd service from running automatically and run rpi-eeprom-update manually.

# Prevent the service from running, this can be run before the
# package is installed to prevent it ever running automatically.
sudo systemctl mask rpi-eeprom-update

# Enable it again
sudo systemctl unmask rpi-eeprom-update

The FREEZE_VERSION option in the EEPROM config file may be used to indicate that the EEPROM should not be updated on this board.

Write protection of EEPROM

There is no software write protection for the boot EEPROM but there will be a mechanism in Raspbian to skip any future updates to the EEPROM. However, it is possible to physically write-protect both EEPROMs via a simple resistor change on the board. Details will be published in the schematics.

EEPROM image files contain a small user-modifiable config file, which may be modified using the rpi-eeprom-config script included in the rpi-eeprom package. See the Bootloader Configuration Page for configuration details.

Checking if an update is available

Running the rpi-eeprom-update command with no parameters indicates whether an update is required. An update is required if the timestamp of the most recent file in the firmware directory (normally /lib/firmware/raspberrypi/bootloader/critical) is newer than that reported by the current bootloader. The images under /lib/firmware/raspberrypi/bootloader are part of the rpi-eeprom package and are only updated via apt update.

sudo rpi-eeprom-update

Reading the current EEPROM configuration

To view the configuration file used by the bootloader at boot time

vcgencmd bootloader_config

Reading the EEPROM version

vcgencmd bootloader_version

Beta firmware

Beta firmware files will be stored in /lib/firmware/raspberrypi/bootloader/beta/. Developers or beta-testers who are comfortable with using the rescue image to fix boot problems can track the beta firmware by editing /etc/default/rpi-eeprom-update

Change FIRMWARE_RELEASE_STATUS="critical"
to FIRMWARE_RELEASE_STATUS="beta"

EEPROM Bootloader configuration options

See the Bootloader Configuration Page for configuration details.

Release Notes