i.MX 8M Mini Yocto 5.0 (Scarthgap)

This section is a guideline how to build a Linux image for the i.MX 8M Mini based congatec modules, using the Yocto Project 5.0 (Scarthgap). The first section contains Linux Host Machine preparation, Yocto obtaining, and Linux image build. The second section describes how to include the software development tools in the target Linux image, and the third section describes how to build a cross-SDK for the Linux Host Machine.
For more information see the i.MX Yocto Project User's Guide

1. Linux image build

To get the Yocto Project expected behavior in a Linux Host Machine, the packages and utilities described below must be installed. An important consideration is the hard disk space required in the host machine. For example, when building on a machine running Ubuntu, the minimum hard disk space required is about 50 GB. It is recommended that at least 120 GB is provided, which is enough to compile all backends together.

The recommended minimum Ubuntu version is 20.04 or later. The latest release supports Chromium v91, which requires an increase to the ulimit (number of open files) to 4098.

1.1 Linux Host Machine preparation

Ubuntu 20.04 or newer is recommended but other environments are also possible.

1.1.1 Ubuntu 20.04

The following tools have to be installed

	$ sudo apt-get update
	$  sudo apt install gawk wget git diffstat unzip texinfo gcc build-essential \
		chrpath socat cpio python3 python3-pip python3-pexpect xz-utils debianutils \
		iputils-ping python3-git python3-jinja2 python3-subunit zstd liblz4-tool file \
		locales libacl1

Regarding the repo tool, it may be necessary to use newer version than the one provided via the operating system package above; the following steps are an example how to get access to such a version

$ mkdir -p ~/.bin
$ PATH="${HOME}/.bin:${PATH}"
$ curl https://storage.googleapis.com/git-repo-downloads/repo > ~/.bin/repo
$ chmod a+rx ~/.bin/repo

1.1.2 Configure the local git

	$ git config --global user.email "youremail"
	$ git config --global user.name "Your name"
	$ git lfs install

1.2 Obtaining Yocto

The Google's repo tool is used to obtain Yocto sources; the tool downloads all necessary files as defined in the provided manifest file. The manifest file therefore determines, among other things, specific version of boot loader and kernel that will be included in the target image. The congatec Yocto sources and subsequently the manifest file are derived from a NXP GA release version; the mapping is in the table below, together with information about included boot loader and kernel version. In addition to the the base manifest file may be available manifest files adding specific functionality above the base NXP GA release. They would be also documented in the table.

Kernel Version	U-boot Version	NXP Release Suffix	Repo Manifest File	Derived congatec Releases	Notes

Kernel Version	U-boot Version	NXP Release Suffix	Repo Manifest File	Derived congatec Releases	Notes
6.6.23-2.0.0	2024.4	2.0.0	cgtsx8m__imx-6.6.23-2.0.0.xml	rel_cgtsx8m_25-04-07-0	The base manifest file

The repo tool dowloads all files into the working directory, so it is a good idea to create a dedicated directory for the purpose, e.g.

	$ mkdir ~/yocto
	$ cd ~/yocto

All manifest files reside on the cgtimx8mm__imx-linux-scarthgap-6.6.23-2.0.0 branch of the manifest-imx8-family repository; the repo init command can be instructed to use either the latest version of the provided manifest file (subsection 1.2a) or a specific version (subsection 1.2b).

1.2a Using the latest available version

    $ repo init -u https://git.congatec.com/arm-nxp/imx8-family/yocto/manifest-imx8-family \
-b cgtimx8mm__imx-linux-scarthgap-6.6.23-2.0.0 \
-m <Repo Manifest File>
    $ repo sync

1.2b Using a specific version

    $ repo init -u https://git.congatec.com/arm-nxp/imx8-family/yocto/manifest-imx8-family \
-b <Git Commit SHA String> \
-m <Repo Manifest File>
    $ repo sync

The Git Commit SHA String is SHA of the commit that contains the desired version of Repo Manifest File

Identification of versions of SW components pertinent to a particular software release is done using Git tag placement inside congatec Git repositories. The Git tag is of the same name as the software release.
The repo tool is not able to use the tag directly, so the commit SHA corresponding to the release tag needs to be used; for convenience we provide a table listing commit SHAs from the manifest-imx8-family repository for the official SW releases.

SW Release	Git Commit SHA String

SW Release	Git Commit SHA String
rel_cgtsx8m_25-04-07-0	90a718b0

1.3 Configuration of the build directory and environment

The downloaded Yocto sources contain imx-setup-release.sh script that is used in this step to configure the build directory and build environment. The script takes three inputs in this example - machine the build is being made for (variable MACHINE), distribution to use (variable DISTRO) and name of the build directory (the -b parameter). The Machine Identification is module dependent and is to be determined as per the table below; regarding distribution the options are fsl-imx-xwayland and fsl-imx-wayland

	$ MACHINE='<Machine Identification>' DISTRO=fsl-imx-xwayland source imx-setup-release.sh -b build-dir
	[ ! ] EULA accept needed for next step.

Module	Machine Identification

Module	Machine Identification
conga-SMX8-Mini Rev A.1/A.2/B.0	imx8mm-cgt-sx8m

Note: The configured environment is not persistent; it can be re-configured using command source setup-environment build-dir

1.4. The fsl-image-validation-imx image building

The last step is the image build itself; the bitbake tool does that, taking at least one parameter - the name of the image to build (i.e. the bitbake image name).

$ bitbake imx-image-core

The available i.MX images are

Image name	Target	Provided by layer

Image name	Target	Provided by layer
core-image-minimal	A small image that only allows a device to boot.	poky
core-image-base	A console-only image that fully supports the target device hardware.	poky
core-image-sato	An image with Sato, a mobile environment and visual style for mobile devices. The image supports a Sato theme and uses Pimlico applications. It contains a terminal, an editor and a file manager.	poky
imx-image-core	An i.MX image with i.MX test applications to be used for Wayland backends. This image is used by our daily core testing.	meta-imx/meta-imx-sdk
fsl-image-machine-test	An FSL Community i.MX core image with console environment - no GUI interface.	meta-freescale-distro
imx-image-multimedia	Builds an i.MX image with a GUI without any Qt content.	meta-imx/meta-imx-sdk
imx-image-full	Builds an opensource Qt 6 image with Machine Learning features.	meta-imx/meta-imx-sdk

After the bitbake finishes, the following files can be found in the tmp/deploy/images/<Machine Identification> subdirectory of the build folder.

File Name	Description

File Name	Description
<bitbake image name>-<Machine Identification>.wic.zst	the complete Linux SD card image
Image	Linux kernel image
<Kernel Default DTB>	the default device tree file

Note that this table does not contain all files in the subdirectory

2. Include SDK in the target image (optional)

Development tools and libraries can be included in the target Linux image, which makes software development on the module itself possible. Yocto's features tools-sdk and dev-pkgs are available for the purpose - after the build directory and environment are configured (i.e. after the step 1.3), the features need to be added to the EXTRA_IMAGE_FEATURES variable in theconf/local.conf file. An example that shows the default variable after the update follows

EXTRA_IMAGE_FEATURES ?= "debug-tweaks tools-sdk dev-pkgs"

The development tools and libraries will be included during the subsequent bitbake run.

3. Build, install, and use the cross-SDK on the Linux Host Machine

The Yocto system is able to build a cross-SDK that can be used for software development on the Linux Host Machine. The command that builds an installation package for the SDK can be invoked after the 1.3 or 1.4 steps.

3.1 Build the cross-SDK installation package

$ bitbake imx-image-core -c populate_sdk

Note: The installation package is located in the tmp/deploy/sdk subdirectory after the build

3.2 Install the SDK

	$ ./tmp/deploy/sdk/fsl-imx-xwayland-glibc-x86_64-core-image-minimal-armv8a-<Machine Identification>-toolchain-6.6-scarthgap.sh

3.3 Source the SDK toolchain

To use the cross-SDK on the Linux Host Machine, the SDK setup file needs to be sourced as follows

	$ source /opt/fsl-imx-xwayland/6.6-scarthgap/environment-setup-armv8a-poky-linux
	$ unset LDFLAGS

Note: The /opt/fsl-imx-xwayland is the default destination directory as proposed by the SDK installer

4. Boot from FSPI

With the above created Linux SD card image the system boots from SD card. It is possible to boot from FSPI onmodule flash if the FSPI bootcontainer is flashed inside the first mtd partition.

A valid FSPI bootcontainer can be built using the Yocto; add the line

UBOOT_CONFIG = "fspi"

into the conf/local.conf Yocto configuration file and run

$ bitbake -C configure imx-boot

The FSPI bootcontainer will be then in the tmp/deploy/images/<Machine Identification> subdirectory, named imx-boot-imx8mm-cgt-sx8m-fspi.bin-flash_evk_flexspi.

Note: The UBOOT_CONFIG line has to be removed then, as it would cause non-booting SD card image after subsequent bitbake runs

Flashing to FSPI could be done in different ways, e.g. from running Linux on module

Copy the bootcontainer to the SD-card to boot from
Boot the system
Erase bootloader partition of SPI-Flash:
$ flash_erase /dev/mtd0 0 0
Copy bootcontainer to flash
$ dd if=<FSPI bootcontainer file> of=/dev/mtd0

i.MX 8 Documentation