Building yocto image for RPi CM4

[Sourabh1107]

Hello All,

This is help request and not a bug/issue reporting.

I recently got my hands on a RPi CM4 Lite and now I want to build Yocto image with barebox as bootloader. I have few doubts before I get started.

1. How should I do the Barebox configuration? For example, for raspberrypi3 we can have machine config in conf/local.conf as:

BAREBOX_CONFIG_raspberrypi3 = "rpi_defconfig"
BAREBOX_IMAGE_SRC_raspberrypi3 = "images/barebox-raspberry-pi-3.img"
COMPATIBLE_MACHINE_pn-barebox_raspberrypi3 = "raspberrypi3"

For RPi CM4, I am using MACHINE="raspberrypi4-64". How should this be used for barebox config?

2. In order to boot from uSD (for CM4 Lite) how should I copy the bootloader files? Will there be any difference between BCM283x RPi like RPi2/3 and BCM2711 based RPi CM4 Lite?

My goal is to build an update with RAUC and Barebox.

Your help will be much appreciated.

Thanks in advance.

[menschel-d]

Hello there, and sorry for the late reply.

After searching through the source code and git history, it seems to me that barebox does not yet support the Raspberry Pi 4 and its variants.

The most recent hint that I've found concerning the support for the Raspberry Pi 4 is the following commit¹ from January 14th.
Its commit message states (among other things):

[...]
The Raspberry Pi 4 support will be ARM64.
[...]

So it seems that support for the Raspberry Pi 4 is still being worked on.

As for your question about where to copy the bootloader files, the official documentation states that the boot process differs from the previous models² and that there is an extra section about the "Raspberry Pi 4 Boot Flow"³.

That should get you started.
Hope it helps.

Remember to tell us the solution once you've found it.

Footnotes

1. https://git.pengutronix.de/cgit/barebox/commit/?id=b267578d0567d26b1bd05d44901f983e0cd167a6 ↩

2. https://www.raspberrypi.com/documentation/computers/raspberry-pi.html#boot-sequence ↩

3. https://www.raspberrypi.com/documentation/computers/raspberry-pi.html#raspberry-pi-4-boot-flow ↩

[a3f]

Raspberry Pi 4 support is included in recent releases like v2022.09.0 provided by meta-barebox. If you know how to build barebox for Raspberry Pi 3, it's exactly the same, but tick Raspberry Pi 4 support as well. The resulting barebox-raspberry-pi.img can be booted on both. You can build barebox for either 32-bit or 64-bit. Not everything works, but SD/Network do (no USB yet though).

To get barebox console working, you'll need to tell the VideoCore about your UART. See the integration in DistroKit for reference:

• https://git.pengutronix.de/cgit/DistroKit/commit/?h=next&id=ae5b35986593310c419bc33eebd9ae7a06de3ffa

It's called rpi2, because it works for all 32-bit targets from 2 onwards, including Raspberry Pi 4. For 64-bit, you just enable CONFIG_64BIT. I didn't have a CM4 to test on, but if you are willing to help out, drop by at the barebox channel on Libera.Chat/Matrix.

Cheers,

[menschel-d]

@Sourabh1107 Have you found a solution by now that you'd like to share with the rest of us?
Is this topic still relevant to you?
If not, I think we can close this help request (after more than 2 years).