Yocto Build for Raspberry Pi 4

Info:

At the time of writing, Yocto dunfell was used. Pl use the latest versions wherever applicable. Build was done in Ubuntu 20.04

STEPS:

• Install the necessary tools

sudo apt install build-essential chrpath diffstat gawk libncurses5-dev python3-distutils texinfo wget git-core diffstat unzip texinfo gcc-multilib socat libsdl1.2-dev xterm

• Checkout the necessary repo to have the basic poky setup

mkdir rpi4
cd ~/rpi4
git clone -b dunfell http://git.yoctoproject.org/git/poky
cd poky
git clone -b dunfell git://git.yoctoproject.org/meta-raspberrypi

• Checkout the add on layer so that you can add any additional recipe

git clone git@github.com:ArivuAlamari/meta-rpi4linux-addon.git

• Add the layers at ~/rpi4/poky/build/temp/bblayers.conf as below

BBLAYERS ?= " \
  /home/your_home/rpi4/poky/meta \
  /home/your_home/rpi4/poky/meta-poky \
  /home/your_home/rpi4/poky/meta-yocto-bsp \
  /home/your_home/rpi4/poky/meta-raspberrypi \
  /home/your_home/rpi4/poky/meta-rpi4linux-addon \
  "

• Update the machine name and build controllers in ~/rpi4/poky/build/temp/local.conf

MACHINE ??= "raspberrypi4-64"
BB_NUMBER_THREADS = "4"
PARALLEL_MAKE = "-j 4"

• Build the SW

cd ~/rpi4/poky/
source oe-init-build-env
bitbake rpi4linux-image

The build takes from 45 min up to 4hrs based on your system speed. It will also takes up to 30Gb. Final results will be stores at

cd ~/rpi4/poky/build/tmp/deploy/images/raspberrypi4-64

SD Card Preparation:

Normally dmesg should tell you the card is sdb or sdc where the microSD is mounted. If it is not sdc, please change the drive name below as it mounts in your system.

• Format the SD card as below

fdisk /dev/sdc
# delete all partitions pre exist in the card
#create 2 primary partions
#change partition 1 to FAT32 type
#change partition 2 to ext4 type
# don't forget to write the changes
# make the filesystem and format
sudo mkfs.vfat /dev/sdc1
sudo mkfs.ext4 /dev/sdc2
# create the partion names as below
sudo fatlabel /dev/sdc1 BOOT
sudo e2label /dev/sdc2 ROOT

• Copy the relevant filed to the partitions

#mount the partions
sudo mount /dev/sdc1 /media/BOOT
sudo mount /dev/sdc2 /media/ROOT
# delete any pre existing files 
cd /media/BOOT
rm -rf *
cd /media/ROOT
rm -rf * 
cd ~/rpi4/poky/build/tmp/deploy/images/raspberrypi4-64/
# copy DTB
sudo cp bcm2711-rpi-4-b.dtb /media/BOOT/
# copy the Linux Image
sudo cp Image /media/BOOT/kernel_rpilinux.img
#copy boot files
cd bootfiles
sudo cp * /media/BOOT/
#copy filesystem
cd /media/ROOT/
sudo tar -xvjf ~/rpi4/poky/build/tmp/deploy/images/raspberrypi4-64/rpi4linux-image-raspberrypi4-64.tar.bz2
 

Update Config Files:

• Update boot config as

sudo vi /media/BOOT/config.txt
kernel=kernel_rpilinux.img
arm_64bit=1
enable_uart=1

• Update boot command as

sudo vi /media/BOOT/cmdline.txt
dwc_otg.lpm_enable=0 console=serial0,115200 console=ttyS0 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait

• fstab file needs to be updated as follows

sudo vi /media/ROOT/etc/fstab
proc                    /proc           proc    defaults          0       0
/dev/mmcblk0p1          /boot           vfat    defaults          0       2
/dev/mmcblo0p2          /               ext4    defaults,noatime  0       1

• Alternatively, you could copy the sample files with above changes to the respective locations as below

sudo cp ~/rpi4/poky/meta-rpi4linux-addon/sample/fstab.sample /media/ROOT/etc/fstab
sudo cp ~/rpi4/poky/meta-rpi4linux-addon/sample/config.txt.sample /media/BOOT/config.txt
sudo cp ~/rpi4/poky/meta-rpi4linux-addon/sample/cmdline.txt.sample /media/BOOT/cmdline.txt

• Finally unmount the SD card

cd ~
sudo umount /media/BOOT
sudo umount /media/ROOT

Testing

• if everything goes well, you will get the boot prompt

username : root
password : 
# no password required. Set the password once you successfully login