Commit 0aaabbb3 authored by David Boddie's avatar David Boddie

Merge branch '67-add-instructions-for-compiling-devkit-kernel' into 'master'

Resolve "Add instructions for compiling devkit kernel"

Closes #67

See merge request !190
parents 5978c7a5 c116bd3c
Pipeline #4235 passed with stages
in 9 minutes and 46 seconds
......@@ -12,6 +12,7 @@ how to perform routine tasks.
HowTo/Bluetooth_Connections
HowTo/Data_Connections
HowTo/Location_Services
HowTo/Rebuilding_the_Kernel
HowTo/Simple_Input_Output
HowTo/SSH_Access
HowTo/Touchscreen
......
Rebuilding the Kernel
=====================
These instructions aim to help you rebuild the kernel for the development board
separately from the process of building a new image in its entirety. It also
covers the process of installing the kernel and other binaries on the board.
The building step can be performed without any modifications to the board.
.. contents::
:local:
Preparations
------------
While it is possible to replace an existing kernel with a new one, you may find
it useful to attach a :ref:`USB to serial adapter <imx8_devkit_usb_to_serial_adapter>`
to the board so that can interact with the bootloader and select a different
kernel to run. This makes it possible to install new kernels alongside the
original one and fall back to the original one if the new ones fail to work.
Installing the Toolchain
------------------------
Install the necessary packages for your system. On Debian-based systems, you
can do this with the ``apt`` tool::
sudo apt install crossbuild-essential-arm64 build-essential gcc-aarch64-linux-gnu bison
On Fedora, use the ``dnf`` tool::
sudo dnf install gcc-aarch64-linux-gnu binutils-aarch64-linux-gnu
It should now be possible to cross-compile the kernel for the development board.
Building the Kernel
-------------------
Clone the `linux-emcraft repository`_ and enter the working directory::
git clone https://source.puri.sm/Librem5/linux-emcraft.git
cd linux-emcraft
For simplicity, we create a directory to hold the modules that will be built::
mkdir _modules
Compile the kernel, optionally using ``ccache`` if installed::
# With ccache:
CROSS_COMPILE='ccache aarch64-linux-gnu-' \
INSTALL_MOD_STRIP=1 INSTALL_MOD_PATH=_modules \
make ARCH=arm64 librem5-evk_defconfig all modules_install
# Without ccache:
CROSS_COMPILE=aarch64-linux-gnu- \
INSTALL_MOD_STRIP=1 INSTALL_MOD_PATH=_modules \
make ARCH=arm64 librem5-evk_defconfig all modules_install
You can also pass the ``-j`` command line option to ``make`` if you want to
compile many files in parallel, specifying the number of parallel builds as an
argument to the option.
Installing the Kernel
---------------------
Connect the development board to a network and find its IP address. Log in as
``root`` and create the ``boot2`` directory inside the existing ``/boot``
directory::
mkdir /boot/boot2
From the workstation, copy the kernel and device tree binary to the board,
replacing ``pureos`` with the IP address of the development board::
scp arch/arm64/boot/Image root@pureos:/boot/boot2/
scp arch/arm64/boot/dts/freescale/librem5-evk.dtb root@pureos:/boot/boot2/dtbs/
Remove the ``source`` and ``build`` symlinks from the modules directory and
copy the directory for the corresponding kernel version to the correct location
on the board, replacing ``$KERNEL_VERSION`` with the version of the kernel that
was built::
rm _modules/lib/modules/$KERNEL_VERSION/source
rm _modules/lib/modules/$KERNEL_VERSION/build
scp -r _modules/lib/modules/$KERNEL_VERSION root@pureos:/lib/modules/
The board should now be ready to reboot into the new kernel.
Booting into U-Boot
-------------------
Plug in the USB to serial adapter and open a serial connection, replacing
``ttyUSB0`` with the appropriate device file if necessary::
picocom -b 115200 /dev/ttyUSB0
Reboot the development board and wait until you see the following text::
Hit any key to stop autoboot:
Press Return and enter the following commands at the U-Boot prompt::
setenv bootdir boot2/
boot
The new kernel should be loaded and run.
To boot into the old kernel, reboot and let it autoboot. This should work as
long as the old kernel image, device tree binary and modules are still
installed.
If you need to restore the system to use a working kernel and bootloader,
follow the instructions in :ref:`imx8_devkit_flashing_emmc`.
.. include:: /links.txt
......@@ -45,6 +45,7 @@ Each voltage is measured against ground (green circle in above image).
3. Plug in the SOM.
.. _imx8_devkit_usb_to_serial_adapter:
Attaching a USB to Serial Adapter
---------------------------------
......
......@@ -151,6 +151,8 @@ It should be possible to log in using ``purism`` as the user name and
$ ssh purism@192.168.42.202
.. _imx8_devkit_flashing_emmc:
Flashing eMMC
-------------
......
......@@ -45,6 +45,7 @@
.. _libhandy documentation : http://honk.sigxcpu.org/projects/libhandy/doc/
.. _libhandy website : https://source.puri.sm/Librem5/libhandy
.. _`Librem 5 developer documentation repository`: https://source.puri.sm/Librem5/developer.puri.sm
.. _`linux-emcraft repository`: https://source.puri.sm/Librem5/linux-emcraft/
.. _`linux-emcraft issue 2`: https://source.puri.sm/Librem5/linux-emcraft/issues/2
.. _`Meson`: https://mesonbuild.com/
.. _`Nightly GNOME Apps`: https://wiki.gnome.org/Apps/Nightly
......
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