View source for Building the Linux Kernel - Cross-compiling for a BeagleBone Black

__NOTOC__
== Building the Linux Kernel - Cross-compiling for a BeagleBone Black ==
=== Install GNU toolchain for the A-Profile Architecture ===
$ cd ~/Downloads<br />
$ Download GNU Toolchain for the A-profile Architecture: 9.2-2019.12 from [https://armkeil.blob.core.windows.net/developer/Files/downloads/gnu-a/9.2-2019.12/binrel/gcc-arm-9.2-2019.12-x86_64-arm-none-linux-gnueabihf.tar.xz here]<br />
$ sudo tar xvf ~/Downloads/gcc-arm-9.2-2019.12-x86_64-arm-none-linux-gnueabihf.tar.xz -C /opt/<br />
$ export CC=/opt/gcc-arm-9.2-2019.12-x86_64-arm-none-linux-gnueabihf/bin/arm-none-linux-gnueabihf-

=== Install Dependencies ===
 $ sudo apt-get install bison flex lzop lzma libmpc-dev u-boot-tools libncurses5-dev:amd64 gettext

 $ mkdir ~/bbb_build
 $ cd ~/bbb_build

=== Test Cross Compiler ===
 $ ${CC}gcc --version
arm-none-linux-gnueabihf-gcc (GNU Toolchain for the A-profile Architecture 9.2-2019.12 (arm-9.10)) 9.2.1 20191025<br />
Copyright (C) 2019 Free Software Foundation, Inc.<br />
This is free software; see the source for copying conditions.  There is NO<br />
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.<br />

=== Bootloader: U-Boot ===
Das U-Boot – the Universal Boot Loader: [http://www.denx.de/wiki/U-Boot U-Boot]<br />
eewiki.net patch archive: [https://github.com/eewiki/u-boot-patches u-boot-patches]<br />

==== Download ====

 $ cd ~/bbb_build
 $ git clone https://github.com/u-boot/u-boot
 $ cd u-boot/
 $ git checkout v2019.04 -b v2019.04

==== Patches ====

 $ cd ~/bbb_build/u-boot
 $ wget -c https://github.com/eewiki/u-boot-patches/raw/master/v2019.04/0001-am335x_evm-uEnv.txt-bootz-n-fixes.patch
 $ wget -c https://github.com/eewiki/u-boot-patches/raw/master/v2019.04/0002-U-Boot-BeagleBone-Cape-Manager.patch
  
 $ patch -p1 < 0001-am335x_evm-uEnv.txt-bootz-n-fixes.patch
 $ patch -p1 < 0002-U-Boot-BeagleBone-Cape-Manager.patch

==== Configure and Build ====

 $ make ARCH=arm CROSS_COMPILE=${CC} distclean
 $ make ARCH=arm CROSS_COMPILE=${CC} am335x_evm_defconfig
 $ make ARCH=arm CROSS_COMPILE=${CC}

=== Linux Kernel ===

<big>This script will build the kernel, modules, device tree binaries and copy them to the deploy directory.</big>

==== Mainline - Download ====
 $ cd ~/bbb_build
 $ git clone https://github.com/RobertCNelson/bb-kernel
 $ cd bb-kernel/


<big>For am33x-rt-v5.4 (Longterm 5.4.x + Real-Time Linux):</big>

 $ git checkout origin/am33x-rt-v5.4 -b am33x-rt-v5.4

==== Build ====
 $ ./build_kernel.sh

=== Development/Hacking: ===

first run (to setup baseline tree): ''./build_kernel.sh'' then modify files under KERNEL directory then run (to rebuild with your changes): ''./tools/rebuild.sh''

=== TI BSP ===
'''Download:'''

 $ cd ~/bbb_build
 $ git clone https://github.com/RobertCNelson/ti-linux-kernel-dev.git
 $ cd ti-linux-kernel-dev/

==== For TI v5.4.x: Real-Time ====

 $ git checkout origin/ti-linux-rt-5.4.y -b tmp

===== Build =====

 $ ./build_kernel.sh

=== Root File System ===
==== Debian 9 ====

User : debian<br />
Password : temppwd

==== Download ====

 $ cd ~/bbb_build
 $ wget -c https://rcn-ee.com/rootfs/eewiki/minfs/debian-10.4-minimal-armhf-2020-05-10.tar.xz

==== Verify ====

 $ sha256sum debian-10.4-minimal-armhf-2020-05-10.tar.xz

==== sha256sum output ====
 cd598e42850cbef87602bf15ee343abfbf0d8c6ba81028c741672b5f24263534  debian-10.4-minimal-armhf-2020-05-10.tar.xz

==== Extract ====

 $ tar xf debian-10.4-minimal-armhf-2020-05-10.tar.xz

=== Setup microSD card ===
We need to access the External Drive to be utilized by the target device. Run '''lsblk''' to help figure out what linux device has been reserved for your External Drive.

 $ lsblk
[[image:dev_sd_card.jpg]]
<br /><br />
Thus you would use:

 $ export DISK=/dev/sdb

Erase partition table/labels on microSD card:

 $ sudo dd if=/dev/zero of=${DISK} bs=1M count=10

=== Install Bootloader ===
 $ cd ~/bbb_build
 $ sudo dd if=./u-boot/MLO of=${DISK} count=1 seek=1 bs=128k
 $ sudo dd if=./u-boot/u-boot.img of=${DISK} count=2 seek=1 bs=384k

=== Create Partition Layout ===

 $ sudo sfdisk ${DISK} <<-__EOF__
 4M,,L,*
 __EOF__

=== Format Partition ===
With mkfs.ext4 1.43, we need to make sure metadata_csum and 64bit are disabled.
As the version of U-Boot needed for this target CAN NOT correctly handle reading files with these newer ext4 options.

 $ sudo mkfs.ext4 -L rootfs -O ^metadata_csum,^64bit ${DISK}1

=== Mount Partition ===
On most systems these partitions may will be auto-mounted...

 $ sudo mkdir -p /media/rootfs/
 $ sudo mount ${DISK}1 /media/rootfs/

=== Backup Bootloader ===
This version of MLO/u-boot.img will be used on the "eMMC" flasher script on this page.

 $ cd ~/bbb_build
 $ sudo mkdir -p /media/rootfs/opt/backup/uboot/
 $ sudo cp -v ./u-boot/MLO /media/rootfs/opt/backup/uboot/
 $ sudo cp -v ./u-boot/u-boot.img /media/rootfs/opt/backup/uboot/

=== Install Kernel and Root File System ===
Copy and paste that "export kernel_version=4.X.Y-Z" exactly as shown in your own build/desktop environment and hit enter to create an environment variable to be used later.

 $ export kernel_version=5.4.70-bone-rt-r38

=== Copy Root File System ===
 $ ~/bbb_build
 $ sudo tar xfvp ./debian-10.4-minimal-armhf-2020-05-10/armhf-rootfs-debian-buster.tar -C /media/rootfs/
 $ sync
 $ sudo chown root:root /media/rootfs/
 $ sudo chmod 755 /media/rootfs/

=== Set uname_r in /boot/uEnv.txt ===
 $ cd ~/bbb_build
 $ sudo sh -c "echo 'uname_r=${kernel_version}' >> /media/rootfs/boot/uEnv.txt"

=== Copy Kernel Image ===
 $ cd ~/bbb_build
 $ sudo cp -v ./bb-kernel/deploy/${kernel_version}.zImage /media/rootfs/boot/vmlinuz-${kernel_version}

=== Copy Kernel Device Tree Binaries ===
 $ cd ~/bbb_build
 $ sudo mkdir -p /media/rootfs/boot/dtbs/${kernel_version}/
 $ sudo tar xfv ./bb-kernel/deploy/${kernel_version}-dtbs.tar.gz -C /media/rootfs/boot/dtbs/${kernel_version}/

=== Copy Kernel Modules ===
 $ cd ~/bbb_build
 $ sudo tar xfv ./bb-kernel/deploy/${kernel_version}-modules.tar.gz -C /media/rootfs/

=== File Systems Table (/etc/fstab) ===
$ sudo sh -c "echo '/dev/mmcblk0p1  /  auto  errors=remount-ro  0  1' >> /media/rootfs/etc/fstab"

=== Networking ===
Edit: /etc/network/interfaces

 $ sudo nano /media/rootfs/etc/network/interfaces

==== Add ====
auto lo<br />
iface lo inet loopback
  
auto eth0<br />
iface eth0 inet dhcp

=== Networking: Using a shared SD card with Multiple BeagleBone ===
To always enable the Ethernet interface as eth0.<br />
Edit: /etc/udev/rules.d/70-persistent-net.rules

 $ sudo nano /media/rootfs/etc/udev/rules.d/70-persistent-net.rules

==== Add ====
<nowiki>#</nowiki> BeagleBone: net device ()<br />
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{dev_id}=="0x0", ATTR{type}=="1", KERNEL=="eth*", NAME="eth0"

=== Remove microSD/SD card ===
 $ sync
 $ sudo umount /media/rootfs

Plug the microSD card in to beaglebone black and press hold "'''Boot Switch'''" button  and power it up.