TS-TPC-7990 Kernel Compile Guide

From embeddedTS Manuals

To add additional driver support, reduce the size of our stock kernel kernel, or to write custom kernel drivers the kernel can be compiled from our sources. The following steps walk through the kernel build process; they are compatible with most of our Linux distributions.

This device has multiple kernels released and available in our git repository:

Newer kernels are released on the linux-tsimx repository:

  • embeddedTS/linux-tsimx
  • The "ts-imx_4.9.11_1.0.0_ga" branch is the only one that should be used with our i.MX6 series.

For legacy kernels:

  • embeddedTS/linux-3.10.17-imx6
  • The "master" branch is 3.10.17 and is largely outdated and replaced with later kernels. This is used with the old Yocto Dora builds.
  • The "imx_3.10.53_1.1.0_ga" kernel is a stable branch. Use this with Yocto Dizzy, Fido, or compatible with Debian Jessie.
  • The "imx_3.14.52_1.1.0_ga" branch is compatible with Yocto Jethro, and Debian.
  • The "imx_4.1.15_1.0.0_ga" branch is compatible with Yocto Jethro, Yocto Morty and Debian. Includes recent fixes not in older branches. This is recommended for most users.

The kernel can be rebuilt by cross compiling from an x86 or x86_64 Linux workstation. Our stock kernels are built with the toolchains built by Yocto. The appropriate cross toolchain for your Linux workstation can be downloaded here:

Note: Older kernels will require older toolchains. For older Yocto kernels use a matching Yocto toolchain. For Debian, the latest toolchain and kernel is recommended. 
chmod a+x poky*.sh
sudo ./poky*.sh

This will ask for the install directory for the toolchain. A custom location can be chosen, however the following instructions will assume the default installation location.

This process will also require several applications for the install/build process. These can be installed on an Ubuntu/Debian workstation with the following command: 

sudo apt-get install git build-essential lzop u-boot-tools libncursesw5-dev fakeroot bc

Once those are installed: 

git clone https://github.com/embeddedTS/linux-tsimx.git -b ts-imx_4.9.11_1.0.0_ga linux-tsimx6 --depth 1

# For legacy kernels instead:
# git clone https://github.com/embeddedTS/linux-3.10.17-imx6.git -b imx_4.1.15_1.0.0_ga linux-tsimx6 --depth 1
# If it is already cloned, the "git pull" command will download and merge the latest changes

# For WiFi support, download qcacld-2.0:
# This is only compatible with 4.1.15 or 4.9.11 kernels
git clone https://github.com/embeddedTS/qcacld-2.0.git -b caf-wlan/CNSS.LEA.NRT_3.1

cd linux-tsimx6
# These export commands must be run every time before any make commands
export ARCH=arm
# For 64-bit
export CROSS_COMPILE=/opt/poky/2.2.2/sysroots/x86_64-pokysdk-linux/usr/bin/arm-poky-linux-gnueabi/arm-poky-linux-gnueabi-
# For 32-bit
#export CROSS_COMPILE=/opt/poky/2.2.2/sysroots/i686-pokysdk-linux/usr/bin/arm-poky-linux-gnueabi/arm-poky-linux-gnueabi-
export LOADADDR=0x10008000
export TEMPDIR=$(mktemp -d)

make ts4900_defconfig

## Make any changes in "make menuconfig" or driver modifications, then compile
make -j8 all uImage zImage

mkdir "$TEMPDIR"/boot/
cp arch/arm/boot/uImage  "$TEMPDIR"/boot/uImage
cp arch/arm/boot/zImage  "$TEMPDIR"/boot/zImage
cp arch/arm/boot/dts/imx6*-ts*.dtb "$TEMPDIR"/boot/
INSTALL_MOD_PATH="$TEMPDIR" make modules_install
make headers_install INSTALL_HDR_PATH="$TEMPDIR"

# Compile wifi driver:
cd ../qcacld-2.0/
export KERNEL_SRC="../linux-tsimx6/"
make clean
CONFIG_CLD_HL_SDIO_CORE=y make -j8
INSTALL_MOD_PATH="$TEMPDIR" make modules_install 

fakeroot sh -c "chmod 755 $TEMPDIR;
	chown -R root:root $TEMPDIR;
	tar cjvf kernel.tar.bz2 -C $TEMPDIR .;
	rm -rvf $TEMPDIR"

This will generate "kernel.tar.bz2" which contains the kernel and necessary modules. It can be installed to the device by copying it to a running unit and executing: 

# Only run this on a device! Not on a workstation!
tar -xf kernel.tar.bz2 -C /

This can also be extracted over existing images from a workstation, or removable media like SD cards. For example, assuming the SD card on a workstation is "/dev/sdc": 

mkdir /mnt/sd/
mount /dev/sdc1 /mnt/sd/
tar -xf kernel.tar.bz2 -C /mnt/sd/
umount /mnt/sd/

Change Kernel Splash Screen

The TS-7990 uses two splash screens. By default they display the same image. U-Boot draws the very first splash screen, and the kernel the second. U-Boot's is only present for about a second while the kernel, device tree, and optionally the FPGA are loaded. The U-Boot splash can be disabled allowing only the kernel's splash screen to show up during boot. This change can be made with: 

# This tells the splash command to just run "true" which returns immediately instead of
# drawing a splash screen
env set splash true
env save

To use a custom logo or splash screen in U-Boot, convert the file to a .bmp, and compress it with gz. The logo should be as small and simple as possible to compress well and load fast.

The imagemagick tool can be used on a host system to convert to the correct format. 

convert yoursplash.png -colors 256 -depth 8 -compress none splash.bmp3
gzip splash.bmp3
# Write to SPI flash
dd if=splash.bmp3.gz of=/dev/mtdblock0 bs=1024 seek=2048

This is provided in U-Boot primarily for applications that may want to give some feedback to the user. For example, a developer may want to use this U-Boot splash as failed to boot screen or to show the user a message while updating from custom U-Boot scripts. In the default configuration when booting off of eMMC or SD the splash screen from U-Boot will only be shown for about 1-3 seconds until the OS kernel is started.

After U-Boot runs, the Linux kernel is typically started which will set up the clock tree and reinitialize hardware. It is not possible for the U-Boot splash to persist through this, but the kernel can redraw the splash a second later which will appear as a short flicker.

The kernel splash screen allows 224 colors. It also allows up to the full screen resolution, but for fastest boot speed it should be kept as small as possible. The image will be centered around a black background.

To convert an image to be compatible with the Linux splash screen, for example, "mylogo.png": 

convert mylogo.png mylogo.ppm
ppmquant 224 mylogo.ppm > mylogo-224.ppm
pnmnoraw mylogo-224.ppm > logo_user_clut224.ppm
cp logo_user_clut224.ppm <kernel build sources>/drivers/video/logo/

In order for this to take effect on boot, the kernel must be re-compiled.

As another option the Linux kernel logo can be disabled completely with "logo.nologo" in the kernel cmdline.

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