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Linux Kernel (2018 April MDK Release)

Critical Link Kernel Repository

Critical Link recommendings using the mityarm-linux-v4.4 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 SDK path may differ):

source <MDK path>/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 linux4.4_rc origin/linux4.4_rc

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 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 modules
make INSTALL_MOD_PATH=../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!)

Make device tree blobs (DTB)

make 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.

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 (Note: Your SDK path may differ):

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

Clone the Git Repository

Clone the repository from ti for the 4.4 Kernel:

git clone git://git.ti.com/graphics/omap5-sgx-ddk-linux.git
cd omap5-sgx-ddk-linux
git checkout ti-img-sgx/1.14.3699939/k4.4

Build the Modules

cd eurasia_km/eurasiacon/build/linux2/omap_linux
make ARCH=arm TARGET_PRODUCT=ti335x KERNELDIR=../../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=../../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 2018 April 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_(2018_April_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

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