These are the instructions to prepare a device for use as a DUT in the Apertis LAVA automated test laboratory. See Reference_Hardware/rpi4_setup for the recommended setup for developers’ devices.

Power control

It is possible to use 5V PSU which can provide at least 2.5A to power the RPi4. According the HAT design guide:

it is possible to power the Pi by supplying 5V through the GPIO header pins 2,4 and GND. The acceptable input voltage range is 5V ±5%.

See the GPIO header pinout at pinout.xyz.

Boot control

The Raspberry Pi 4 OTP first stage bootloader is using a second stage located in the EEPROM chip.

Depending on the boot mode flashed into SPI EEPROM the second stage bootloader is able to boot the DUT from SD-card, USB mass storage device or network.

Flash EEPROM for network boot

Do the initial setup as described in rpi4_setup.

Low level tuning of bootrom is possible with the tools from rpi-eeprom package. A distribution which ships the rpi-eeprom package is needed, for instance NOOBS, Raspbian or Ubuntu. Boot the RPi4 device with a selected distro and proceed in terminal.

Check the list of available stable bootroms and export variable with the last available version, for example:

PI_EEPROM_VERSION=2021-04-29

Download the bootrom:

wget https://github.com/raspberrypi/rpi-eeprom/raw/master/firmware/stable/pieeprom-${PI_EEPROM_VERSION}.bin

Extract and save the default config:

rpi-eeprom-config pieeprom-${PI_EEPROM_VERSION}.bin > bootconf.txt

Change the bootrom configration file bootconf.txt with any editor according documentation.

The configuration below is forcing the board to use network boot only and use bcm2711-rpi-4-b directory on server side to search boot files:

[all]
BOOT_UART=1
WAKE_ON_GPIO=1
POWER_OFF_ON_HALT=0
BOOT_ORDER=0xf2
TFTP_PREFIX=1
TFTP_PREFIX_STR=bcm2711-rpi-4-b/

Generate the bootrom with updated config:

rpi-eeprom-config --out pieeprom-${PI_EEPROM_VERSION}-my.bin --config bootconf.txt pieeprom-${PI_EEPROM_VERSION}.bin

As root user install the bootrom for flashing the device on next boot:

sudo rpi-eeprom-update -d -f ./pieeprom-${PI_EEPROM_VERSION}-my.bin

The above command will put the files below under /boot:

recovery.bin – second stage bootloader capable to flash the FW
pieeprom.upd and pieeprom.sig – prepared FW second stage bootloader to be flashed into EEPROM and its sha256 checksum

After reboot the new bootrom will be flashed.

Second stage bootloader

After setting the configuration as described above, the common directory bcm2711-rpi-4-b will be used on TFTP server to search boot files for all RPi 4 devices.

The boot directory bcm2711-rpi-4-b/ must contain files used for the second stage bootloader (see the contents of /boot from package raspi-firmware).

In addition, the DTB file bcm2711-rpi-4-b.dtb from the kernel used in Apertis and the config.txt boot configuration needs to be copied under the same bcm2711-rpi-4-b/ directory. The description of variables for config.txt is available online. For Apertis we use singe bootable U-Boot image for RPi3 and RPi4, 64b OS and upstream kernel, hence a minimal config.txt file should look like this:

kernel=u-boot.bin

# Switch the CPU from ARMv7 into ARMv8 (aarch64) mode
arm_64bit=1

# Use dtb with upstream names
upstream_kernel=1

# Enable serial console
enable_uart=1

# Forced core frequency to allow correct work of UART both
# for RPi 3 and 4 with DTB from upstream kernel
[pi3]
core_freq=250

[pi4]
core_freq=500
core_freq_min=500

U-Boot binary

We are using U-Boot binary from the package u-boot-rpi with minimal version 2020.04+dfsg-2co3 which has all features required for Apertis. It is possible to use single unified binary /usr/lib/u-boot/rpi_arm64/u-boot.bin suitable for both RPi3 and RPi4 or use a dedicated U-Boot for each board version (need to set the kernel variable separately per board in config.txt file).

The u-boot.bin should be placed alongside the other boot files, so the minimal files subset in the boot directory should contain the following files:

bcm2711-rpi-4-b.dtb
bootcode.bin
config.txt
fixup4.dat
start4.elf
u-boot.bin

OS Boot

With the setup above the U-Boot is responsible for loading kernel and initramfs according the configuration provided by extlinux/extlinux.conf or boot commands for U-Boot set in LAVA job.

For health check the same network boot configuration may be used as we use for Renesas boards with minimal kernel v5.10.x.

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