Linux Kernel (2020 August MDK Release)¶

Critical Link Kernel Repository¶

Critical Link recommends using the linux4.19_wip branch on our git server: git://support.criticallink.com/home/git/linux-mityarm-335x.git (Gitweb)

Configuring the Kernel Build Environment¶

Setup the MDK environment (Note: Your MDK path may differ):

source <MDK path>/environment-setup-cortexa8hf-neon-criticallink-linux-gnueabi

If the MDK is installed to the default directory:

source /opt/criticallink/mitysom-335x_2020-08-20/environment-setup-cortexa8hf-neon-criticallink-linux-gnueabi

Building the Kernel¶

Clone the repository from Critical Link:

git clone git://support.criticallink.com/home/git/linux-mityarm-335x.git
cd linux-mityarm-335x
git checkout -b linux4.19_wip origin/linux4.19_wip

Note: You may need to run

git fetch

if the branch wasn't cloned.

Configure the build for the Development Kit Baseboard

make mitysom-335x-devkit_defconfig

Optional: Customize the kernel

make menuconfig

Build the kernel image

make -j$(nproc) zImage

For a faster build, add "-j$(nproc)" to build with multiple threads, @$(nproc) will use as many threads as the building machine has cores.

Make the kernel modules

make -j$(nproc) modules
make INSTALL_MOD_PATH=$PWD/../rootfs/ modules_install

This will build the selected kernel modules and then install them under ../rootfs/. You can change this path to change where the modules will install. For example, you may have the build install directly to an SD card. (Note: Make sure you include the INSTALL_MOD_PATH variable. Otherwise, the kernel Makefile will attempt to install these modules into your host machine's root filesystem. You probably do NOT want this!)

After running the modules_install command, the kernel modules will be in, for example, ../rootfs/lib/modules/4.19.38-gf4a1a195ea50-dirty. The actual directory name may be different due to differences in your kernel version. You must copy the directory in ../rootfs/lib/modules to your filesystem under /lib/modules.

Make device tree blobs (DTB)

make -j$(nproc) dtbs

You will find the compiled DTBs in arch/arm/boot/dts.
Note: These will be in the same folder as the source files. Make sure to use the .dtb file and not the .dts or .dtsi.

In most cases, you will need to move your dtb file to the boot partition on your filesystem (or create a fitImage as described in the Flattened Image Tree section).

Install PowerVR SGX Graphic Modules¶

If you are building your own kernel and want to enable SGX graphics then you must add the modules to the filesystem manually.

Configuring the Build Enviroment¶

Setup the MDK environment:

source <MDK path>/environment-setup-cortexa8hf-neon-criticallink-linux-gnueabi

If the MDK is installed in the default directory:

source /opt/criticallink/mitysom-335x_2020-08-20/environment-setup-cortexa8hf-neon-criticallink-linux-gnueabi

Clone the Git Repository¶

Clone the repository from ti for the 4.19 Kernel:

git clone git://git.ti.com/graphics/omap5-sgx-ddk-linux.git
cd omap5-sgx-ddk-linux
git checkout ti-img-sgx/1.17.4948957/k4.19

Build the Modules¶

cd eurasia_km/eurasiacon/build/linux2/omap_linux
make ARCH=arm TARGET_PRODUCT=ti335x KERNELDIR=$PWD/../../linux-mityarm-335x

Where KERNELDIR points to the directory where you built your kernel.

make -C ${KERNELDIR} SUBDIRS=${PWD}/../../../binary2_omap_linux_release/target/kbuild INSTALL_MOD_PATH=$PWD/../../rootfs modules_install

Where:

• KERNELDIR is the directory where you built your kernel.
• SUBDIRS points to the full path of the kbuild directory.
• INSTALL_MOD_PATH points to the directory containing the root filesystem you are using.

The modules should have been installed under lib/modules/4.4.32-xxxxx/extra/ in your filesystem. The modules that should be in the extra directory are bc_example.ko and pvrsrvkm.ko.

Enabling the Modules¶

At startup you can run the following modprobe command to enable the modules.

modprobe pvrsrvkm

Flattened Image Tree (FIT)¶

The 2020 August MDK provides a FIT. This FIT contains the devkit kernel and device tree.

Building mkimage¶

Follow the instructions for checking out the MDK U-Boot source, https://support.criticallink.com/redmine/projects/armc8-platforms/wiki/Das_U-Boot_Port_(2020_August_MDK_Release)#Checkout-U-Boot

Build U-Boot tools

cd <work directory>/u-boot-mityarm-335x
make tools

Add U-Boot tools to your path

export PATH=$(pwd)/tools:$PATH

Preparing the FIT source¶

Copy the FIT source to the kernel source directory

cd <work directory>/linux-mityarm-335x
cp <MDK path>/sources/fitImage.its ./

The FIT source is provided by Yocto and has a slightly different set up than the kernel source.

Open fitImage.its and change the following line:

data = /incbin/("linux.bin");

to

data = /incbin/("arch/arm/boot/zImage");

Building the FIT¶

Run mkimage

mkimage -f fitImage.its fitImage