CM-T54: Linux: Kernel

Overview

Linux kernel for CM-T54 modules provides support for on-board peripherals and abstracts the functionality provided by the hardware. Current support coverage is specified at O/S support coverage map page. CompuLab provides ready-to-run binary kernel images, and source code of the modifications and additions made to the Linux kernel to work properly with CM-T54 modules.

Building kernel for CM-T54

Cross-Compiler

There are several options for cross-compilation toolchain setup. You can either compile your cross-compiler or use an already built cross-compiler. The cross-compiler should support the ARM embedded-application binary interface ("EABI")

• Pre-built toolchain (recommended):
  • Sourcery CodeBench Lite
• Tools for creating cross-compilers:
  • Crosstool-ng: Builds a cross-compiler from source. Non-distribution specific.
  • Crossdev: Gentoo's cross-compiler builder. Needs Gentoo.

Getting kernel sources

We assume that you have created /home/development/cm-t54/kernel directory for CM-T54 kernel development.

Git clone

• Install git version control system.
• Create a clone of linux kernel tree

cd /home/development/cm-t54/kernel
git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git linux-cm-t54

• Create a branch for CM-T54 development. The CM-T54 patches are generated vs. v3.14 tag (455c6fdbd219161bd09b1165f11699d6d73de11c commit) in the Linux tree. It is recommended to use exactly the same baseline to avoid merge conflicts.

cd /home/development/cm-t54/kernel/linux-cm-t54
git checkout -b cm-t54-dev v3.14

• Apply the CM-T54 patch

git apply /path/to/cm-t54-linux/kernel/linux-3.14-cm-t54-1.patch

Future stable kernel versions of 3.14 can also be used by checking out any later tag of v3.14.y stable kernel tree.

Building the kernel

export ARCH=arm
export CROSS_COMPILE=arm-none-linux-eabi-
make cm_t54_defconfig
make menuconfig
make && make zImage && make omap5-sbc-t54.dtb \
     INSTALL_MOD_PATH=/home/development/cm-t54/rootfs make modules_install

In the example above:

• The Linux kernel image zImage will be created in /home/development/cm-t54/kernel/linux-cm-t54/arch/arm/boot
• The Device Tree binary omap5-sbc-t54.dtb will be created in /home/development/cm-t54/kernel/linux-cm-t54/arch/arm/boot/dts
• The loadable kernel modules will be installed into the /home/development/cm-t54/rootfs/lib/modules directory.

When the CM-T54 is booted with the kernel image and Device Tree binary created as described above and with networked root filesystem at /home/development/cm-t54/rootfs/, the system will be able to load the kernel modules properly, thus avoiding module version problems.

See also

• CM-T54: Linux: Getting started
• CM-T54: Linux: Debian