Building a Yocto Image for RPi CM4 Integrating the Sona IF573 PCIe Wi-Fi Module

Purpose

This document provides step-by-step guidance on how to build a Linux image with Yocto release Scarthgap for the Raspberry Pi CM4 Compute Module including Ezurio's Sona IF573 PCIe Wi-Fi M2 card (Part Number 453-00120).

Scope

This document concentrates on Wi-Fi functionality. Integrating Bluetooth functionality will be addressed in subsequent revisions.

Prerequisites

This document assumes that the user has basic knowledge about Linux and Yocto software and Raspberry Pi hardware.

Required Hardware

Ubuntu 22.04 PC with internet connection for cross-compiling the Yocto image
Raspberry Pi CM4 IO board with CM4 module
(https://www.raspberrypi.com/products/compute-module-4-io-board/)
Sona IF573 DVK
(https://www.ezurio.com/part/453-00120-k1)
https://www.ezurio.com/wireless-modules/wifi-modules-bluetooth/sona-if573-wi-fi-6e-bluetooth-core-6-0-module
Note: The Sona-IF573 M2 Wi-Fi module requires a 32kHz SUSCLK signal on pin50 which is not supplied by the CM4. This DVK provides that signal to the module.
1xPCIe to miniPCIe adapter
https://www.conrad.com/en/p/renkforce-gbic-1x-mini-pci-express-1x-pci-express-408870.html
miniPCIe to M2 E-key adapter
https://www.delock.de/produkt/63909/merkmale.html?setLanguage=en

Note: both of the above adapters were used on top of each to connect the Sona-IF573 M2 card to the PCIe slot of the RPi CM4 IO board. There might be a single adapter solution in the market though.

USB to serial converter to attach to the debug UART of the Raspberry Pi
For example: https://www.berrybase.de/usb-ttl-uart-rs232-adapterkabel-mit-pl2303hx-chipsatz/

Complete hardware setup

Software Installation

Preparation of Yocto build environment and first build

Update build PC

sudo apt update
sudo apt install gawk wget git diffstat unzip texinfo gcc-multilib \
build-essential chrpath socat cpio python3 python3-pip python3-pexpect \
xz-utils debianutils iputils-ping python3-git python3-jinja2 libegl1-mesa \
libsdl1.2-dev pylint xterm

Clone Yocto environment

mkdir -p ~/yocto/cm4
cd ~/yocto/cm4
git clone -b scarthgap git://git.yoctoproject.org/poky
cd poky
git clone -b scarthgap https://github.com/agherzan/meta-raspberrypi.git 
git clone -b scarthgap git://git.openembedded.org/meta-openembedded

Configuration for first boot

Enter build environment

source oe-init-build-env

Add layers to conf/bblayers.conf by executing these commands in the build directory

bitbake-layers add-layer ../meta-openembedded/meta-oe
bitbake-layers add-layer ../meta-openembedded/meta-python
bitbake-layers add-layer ../meta-openembedded/meta-networking
bitbake-layers add-layer ../meta-raspberrypi

Set machine and options by editing conf/local.conf

At the end of local.conf add:

# added for CM4 build
MACHINE = "raspberrypi4-64"
ENABLE_UART = "1"
ENABLE_SPI_BUS = "1"
ENABLE_I2C = "1"
IMAGE_INSTALL:append = " python3"

Build image

bitbake core-image-minimal

Note: This will take quite a while. Fetch errors can often be overcome by simply repeating the bitbake process.

Successful build:

Integrating the Sona IF573

Placing Ezurio meta-layer

cd ..
git clone https://github.com/Ezurio/meta-summit-radio/ 
cd meta-summit-radio
git checkout lrd-12.103.0.x
cd ..
source oe-init-build-env

Note: at the time of using this document newer releases might be available. Feel free to use the latest: https://github.com/Ezurio/Connectivity_Stack_Release_Packages/releases

Adding Ezurio meta-layer to conf/bblayers.conf

execute this command in the build directory:

bitbake-layers add-layer ../meta-summit-radio/meta-summit-radio

Patches

Two patches are required for running the Sona-IF573 on the Raspberry Pi CM4:

0001-PATCH-PCIe-Bring-up-for-Rpi-CM4.patch
0002-PATCH-brcmfmac-Set-PCI-dma-mask-to-64-bits.patch

https://www.ezurio.com/documentation/rpi-cm4-patches

Download the patches and extract them to:

../poky/meta-summit-radio/meta-summit-radio/recipes-bsp/summit-backports/files

Modify to add the patches:

../poky/meta-summit-radio/meta-summit-radio/recipes-bsp/summit-backports/summit-backports.inc

The following section must be modified as shown in the second code block:

SRC_URI += "\
    ${SUMMIT_URI}/summit-backports-${PV}.tar.bz2;name=summit-backports \
    file://0001-fix-genlmsg_multicast_allns.patch \
    file://0002-Fixed-UBSAN-out-of-bounds-errors.patch \
    file://0003-brcmcfmac-Demote-DPC-error-message.patch \
    file://0004-Fix-stop-shutdown-mode-entry.patch \
    "

Edit it as shown below:

SRC_URI += "\
    ${SUMMIT_URI}/summit-backports-${PV}.tar.bz2;name=summit-backports \
    file://0001-fix-genlmsg_multicast_allns.patch \
    file://0002-Fixed-UBSAN-out-of-bounds-errors.patch \
    file://0003-brcmcfmac-Demote-DPC-error-message.patch \
    file://0004-Fix-stop-shutdown-mode-entry.patch \
    file://0001-PATCH-PCIe-Bring-up-for-Rpi-CM4.patch \
    file://0002-PATCH-brcmfmac-Set-PCI-dma-mask-to-64-bits.patch \
    "

Configure Backports

bitbake -c menuconfig kernel-module-lwb-if-backports

enableCustom PCIE BAR window size support for FullMac driver

Navigate the menu as follows:

Wireless LAN --->Broadcom devices----Custom PCIE BAR window size support for FullMAC driver

Configure Linux kernel

bitbake -c menuconfig virtual/kernel

Choose disable Bluetooth subsystem support as it is put into the kernel by Backports.

Navigate the menu as follows:

Networking support --->Bluetooth subsystem support ----

Next, set Wireless <M>

Navigate the menu as follows:

Networking support --->Wireless --->cfg80211 - wireless configuration API

remove other Wireless LAN drivers (but NOT the subsystem “Wireless LAN”)

Adding required Ezurio recipes to conf/local.conf

At the end of local.conf add:

# added for IF573
IMAGE_OVERHEAD_FACTOR = "6" 

CORE_IMAGE_EXTRA_INSTALL += "\
	packagegroup-tools-bluetooth \
	pulseaudio \
	hostapd \
	iptables \
	iperf3 \
	tftp-hpa \
	htop \
	lighttpd \
	libedit \
	libnl \
	libnl-route \
	tcpdump \
	dhcpcd \
	bridge-utils \
	openssl \
	ebtables \
	iw \
	ethtool \
	pciutils \
    usbutils \
	kernel-module-lwb-if-backports \
	if573-pcie-firmware \
	summit-supplicant-lwb-if \
	summit-networkmanager-lwb-if \
"
# Note: not all of above packages are a hard requirement but they can make the life easy.

PREFERRED_RPROVIDER_wpa-supplicant = "summit-supplicant-lwb-if"
PREFERRED_RPROVIDER_wpa-supplicant-cli = "summit-supplicant-lwb-if-cli"
PREFERRED_RPROVIDER_wpa-supplicant-passphrase = "summit-supplicant-lwb-if-passphrase"

PREFERRED_PROVIDER_wireless-regdb-static = "wireless-regdb"

LWB_REGDOMAIN = "ETSI"

#not needed when using serdev for Bluetooth
BT_SERIAL_PORT = "/dev/ttyUSB0"

Please note, the summit-supplicant is named ”sdcsupp”, not “wpa_supplicant”.

Building RPi CM4 Linux image for Sona-IF573

bitbake core-image-minimal

This will take another while. Again, fetch errors can often be overcome with another try.

Successful build:

Flashing Linux image to CM4 eMMC memory

Compiling usbboot to mount eMMC memory as USB drive

Make sure you have the libusb library installed:sudo apt install libusb-1.0-0-dev

Download the Raspberry Pi usbboot repository:

$ git clone --depth=1 https://github.com/raspberrypi/usbboot

Change directory into the usbboot directory and build rpiboot:

$ cd usbboot
$ make

Now there should be an rpiboot executable in the directory.

Flashing the CM4

For this the CM4 must be put into USB mass storage mode.

Place a jumper on J2 across pins 1 and 2 and connect the microUSB port of the IO board to your Ubuntu development PC.

To mount the eMMC storage, run:

$ sudo ./rpiboot

Then, with lsblk you should see that your CM4 eMMC memory is mounted as a block device (sdb in this case):

Locate the generated Linux image:

../poky/build/tmp/deploy/images/raspberrypi4-64
ls *.wic.bz2 -al
-rw-r--r-- 2 alex alex 92657639 Jun 24 17:07 core-image-minimal-raspberrypi4-64.rootfs-20250624144522.wic.bz2
lrwxrwxrwx 2 alex alex       64 Jun 24 17:07 core-image-minimal-raspberrypi4-64.rootfs.wic.bz2 -> core-image-minimal-raspberrypi4-64.rootfs-20250624144522.wic.bz2

Unpack it as follows:

bunzip2 -f core-image-minimal-raspberrypi4-64.rootfs.wic.bz2

Use dd to flash the memory.

Make sure to select the block device that was created for your Raspberry Pi!

sudo dd if=core-image-minimal-raspberrypi4-64.rootfs.wic of=/dev/sdb bs=1M conv=sync

After successful download of the image, carefully remove the jumper on J2 and the microUSB cable and remove power.

Set up hardware and apply power to both boards:

With iw dev you now should see that the Wi-Fi interface was created: