Updating the Raspberry Pi 4 bootloader

[kkaempf]

Reading the Raspberry Pi documentation I came across updating the bootloader which is stored in an EEPROM on RPi4.

(adding documentation label as this needs to be clearly documented)

Is your feature request related to a problem? Please describe.

RPi 3 has the bootloader in bootcode.bin on the first FAT partition. Updating it just needs a new cOS image.

However, RPi4 stores the bootloader in an on-board EEPROM and needs to run a bootloader-update binary.

Describe the solution you'd like

• cOS needs to treat the bootloader as part of the operating system layer and flag new versions as OS updates
• probably needs to report the bootloader version as part of the OS layer software manifest (?)
• booting cOS (on RPi4 !) with a new bootloader needs to
  • detect that a new bootloader is present
  • run the update-bootloader binary to store the update in EEPROM
  • reboot (with the new bootloader)

Describe alternatives you've considered

None

Additional context

See links above

[dragonchaser]

I am not sure if we should implement that, the bootloaders are usually fine for ages. Messing with peoples hardware might have unwanted implications. If somebody wants to update the firmware of the device, it is usually easy to quickly run a official raspbian image and do that through raspi-config.

[kkaempf]

Well, we should at least have documentation and a plan, in case someone wants to mass-deploy RPi4s (or similar edge systems).

[kkaempf]

Further down in the docs, I find this:

recovery.bin

At power on, the BCM2711 ROM looks for a file called recovery.bin in the root directory of the boot partition on the SD card. If a valid recovery.bin is found then the ROM executes this instead of the contents of the EEPROM. This mechanism ensures that the bootloader EEPROM can always be reset to a valid image with factory default settings.

This would mean it's sufficient to provide the latest bootcode in recovery.bin