Trim-Slice Linux Kernel

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The Trim-Slice Linux kernel provides support for on-board peripherals and abstracts the functionality provided by the hardware. Currently supported features are specified at the Supported Features 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 the Trim-Slice.

Kernel boot process

Default boot process

The Trim-Slice U-Boot scans the various boot devices and loads the kernel from the first valid boot device. The boot device is valid when:

  • physically present
  • formatted with ext2/ext3 or vfat
  • has uImage and boot.scr files in / or in /boot directory

Default boot device layout

The Trim-Slice default boot device layout:

  • /boot/uImage - Trim-Slice Linux kernel
  • /boot/boot.scr - U-Boot boot script that selects correct kernel boot parameters and loads the kernel
  • / - root file system

Boot device scan order

The boot script (/boot/boot.scr) will attempt to boot from the various boot devices according to the following order:

  • Front SD card
  • External USB storage
  • Micro-SD card
  • Internal SATA storage

Custom boot process

The default Trim-Slice boot process can be overridden by setting custom bootargs and bootcmd U-boot variables:

bootargs variable

This variable defines kernel command line:

mem=384M@0M mem=512M@512M nvmem=128M@384M vmalloc=248M video=tegrafb console=ttyS0,115200 
  • For internal SATA add:
root=/dev/sda1 nohdparm rootwait rw 
  • For micro-SD add:
root=/dev/mmcblk0p1 rw 
  • For NFS add:
root=/dev/nfs nfsroot=your_host:/your_rootfs_path,v3 ip=dhcp rw

bootcmd variable

This variable defines kernel load mechanism:

  • For internal SATA set:
usb start 1 && ext2load usb 0:1 4080000 /boot/uImage && bootm 4080000
  • For micro-SD set:
mmc init 1 && ext2load mmc 1 4080000 /boot/uImage && bootm 4080000
  • For TFTP boot set:
dhcp; setenv serverip your_server_ip; tftp 4080000 uImage; bootm 4080000

Building the Trim-Slice kernel


For Trim-Slice kernel compilation we recommend to use CodeSourcery 2009-q1 cross-compiler. Install the cross-compiler by following the instructions below:

cd /home/development/cross-tools/
tar xvjf arm-2009q1-203-arm-none-linux-gnueabi-i686-pc-linux-gnu.tar.bz2

U-Boot mkimage tool

The U-Boot mkimage utility creates kernel images that can be loaded by the Trim-Slice boot-loader. You can download the pre-built mkimage binary or build it yourself:

mkdir ~/tmp
cd tmp
tar -xjvf u-boot-latest.tar.bz2
cd u-boot-2009.08
touch include/config.{h,mk}
make tools
sudo install tools/mkimage /usr/local/bin

Getting kernel sources

The Trim-Slice kernel is publicly available on hosting. There are two ways to get Linux kernel sources that can be used as a baseline for Trim-Slice kernel. You can either create a copy of trimslice-kernel git tree or download a snapshot and extract it.

Admolition note.png The following instructions assume that you have created /home/development/trimslice/trimslice-kernel directory for Trim-Slice kernel sources.

Snapshot download

  • Download the latest release trimslice-l4t.r15.01 tag snapshot with your web browser.
  • Extract the downloaded archive into the /home/development/trimslice/trimslice-kernel directory.

Git clone

  • Install git version control system.
  • Create a clone of trimslice-kernel tree
cd /home/development/trimslice/
git clone trimslice-kernel
cd trimslice-kernel
git checkout -b trimslice/l4t.r15.01-dev trimslice-l4t.r15.01
See the full list of supported release/development tags below:

Building the kernel

In the example below, the Linux kernel image (uImage) will be created in trimslice-kernel/arch/arm/boot, and the loadable kernel modules will be installed into the trimslice-kernel/modules_install/lib/modules directory.

export ARCH=arm
export CROSS_COMPILE=arm-none-linux-gnueabi-
export PATH=${PATH}:"/home/development/cross-tools/arm-2009q1/bin/"

cd /home/development/trimslice/trimslice-kernel
make trimslice_defconfig
make uImage 
make modules 
INSTALL_MOD_PATH=./modules_install make modules_install

Deploying the kernel

  • Copy /home/development/trimslice/trimslice-kernel/arch/arm/boot/uImage into the boot device /boot directory.
  • Copy /home/development/trimslice/trimslice-kernel/modules_install/ into the boot device / directory.

See also

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