Development

TFTP boot

During kernel development, it can be useful to not have to reflash the board every time you generate a new kernel image. We support TFTP kernel boot via u-boot. Only the client side is described here. The installation and configuration of a TFTP server is not described in this document.

Enabling TFTP boot

TFTP boot can be enabled from within U-Boot shell or from Linux userspace.

Enabling in Linux

To be able to modify the u-boot environment from within the Linux userspace, you need to make sure you have included u-boot-env and u-boot-fw-utils as part of your image.

For instance you can add the following to your local.conf file:

IMAGE_INSTALL:append = " \
        u-boot-env \
        u-boot-fw-utils \
"

In the Linux userspace you can run the following command to enable TFTP boot:

fw_setenv force_tftpboot 1

Enabling in U-Boot

To enable TFTP boot from within the u-boot shell, you can run the following command:

setenv force_tftpboot 1

Disabling TFTP boot

Once you want to disable TFTP boot and start booting again the kernel present in the kernel partition of the mass storage, you can run one of the following commands:

Disabling in Linux

fw_setenv force_tftpboot 0

Disabling in U-Boot

setenv force_tftpboot 0

Network configuration

U-Boot is using staticly defined IPs to connect to the TFTP server. DHCP is not supported yet. You can see the configuration below:

Machine	IP
Client (U-Boot)	192.168.96.1/24
Server (Your machine)	192.168.96.20/24

Building Linux outside of Yocto

When making changes to the Linux kernel, it can be useful to build it outside of yocto. This allow to quickly do build changes without having to rebuild the full kernel everytime. This section describes how to build a fitImage that can be flashed or downloaded via TFTP boot without yocto.

Setting up Rity SDK

Firstly, you need to do the Rity SDK first time setup.

Do the following steps:

Downloading the RITY SDK
Generation of the build configuration
Building an image

Setting up the environment

A few variables need to be defined in order to run the commands below to build the kernel.

MACHINE=i500-pumpkin
RITYDIR=/path/to/rity
IMAGENAME=core-image-weston
export ARCH=arm64
export CROSS_COMPILE=aarch64-linux-gnu-
export DTC_FLAGS=-@

Please modify MACHINE, RITYDIR, IMAGE and CROSS_COMPILE to fit your setup.

Setting up cross compiler

Make sur to have generated the build configuration, see Setting up Rity SDK. To build the toolchain installer for a standard SDK and populate the SDK image, use the following command:

cd $RITYDIR/build
bitbake $IMAGENAME -c populate_sdk

Execute script and install it wherever you want by replacing PATH_TO_MY_SDK with your own chosen path.

cd tmp/deploy/sdk
./rity-bringup-glibc-x86_64-core-image-weston-aarch64-i500-pumpkin-toolchain-22.0-dev.sh
Rity bringup SDK installer version 22.0-dev
===========================================
Enter target directory for SDK (default: /opt/rity-bringup/22.0-dev): PATH_TO_MY_SDK
You are about to install the SDK to "PATH_TO_MY_SDK". Proceed [Y/n]? y
Extracting SDK.....................................................................................................................................................................................................................done
Setting it up...done
SDK has been successfully set up and is ready to be used.
Each time you wish to use the SDK in a new shell session, you need to source the environment setup script e.g.
 $ . PATH_TO_MY_SDK/environment-setup-aarch64-poky-linux
 $ . PATH_TO_MY_SDK/environment-setup-armv7at2hf-neon-pokymllib32-linux-gnueabi

Then, source the SDK:

. PATH_TO_MY_SDK/environment-setup-aarch64-poky-linux
. PATH_TO_MY_SDK/environment-setup-armv7at2hf-neon-pokymllib32-linux-gnueabi

Cloning Linux

git clone https://gitlab.com/mediatek/aiot/bsp/linux.git

Alternatively if you already have a Linux repository cloned, you can add the rity remote:

cd /path/to/linux
git remote add rity https://gitlab.com/mediatek/aiot/bsp/linux.git

Note

Don’t forget to install all prerequist to build kernel: https://www.kernel.org/doc/html/latest/process/changes.html

Installing .config file

The kernel configuration used by yocto is a merge of the Linux ARM64 defconfig and config fragments that can be found in recipes-kernel/linux/linux-mtk. To install the generated yocto defconfig you can run the following commands:

cd linux
$RITYDIR/src/meta-mediatek-bsp/scripts/copy_kernel_config.sh $RITYDIR $MACHINE $IMAGENAME
Copying kernel config to i500-pumpkin-config...
mv i500-pumpkin-config .config

The commands above will retrieve the .config from the existing i500-pumpkin build and copy it at the root of your linux repository.

Generating the image-tree script

fitImage are created using image-tree scripts (its). A template exists under docs/kernel-fitimage.its.

In order to generate the correct image-tree script for the MACHINE you are using, please run the following command:

$RITYDIR/src/meta-mediatek-bsp/scripts/generate_kernel_its.sh $RITYDIR $MACHINE $IMAGENAME

Building the kernel fitImage

make
mkimage -f $MACHINE.its fitImage