Crystalfontz boards support in Yocto

The Yocto 1.5 release is approaching and the Freescale layer trees are now frozen.
Bootlin added support for the various Crystalfontz boards to that release as you can check on the OpenEmbedded metadata index.

Yocto Project

First some preparative work has been done in the meta-fsl-arm layer in order to add the required features to generate an image able to boot on the Crystalfontz boards:

  • Support for a newer version of the Barebox mainline, 2013.08.0. As the previously supported version of Barebox was too old, it didn’t include support for the Crystalfontz boards. Also, some work has been done to make the recipe itself more generic so that custom layers can reuse it more easily.
  • Inclusion of the patches allowing the imx-bootlets to boot Barebox. The imx-bootlets were only able to boot U-Boot or the Linux kernel until now.
  • Creation of a new image type, using the imx-bootlets, then Barebox to boot the Linux kernel. All the boards based on a Freescale mxs SoC (i.mx23 and i.mx28) will benefit of this new image type. This is actually the difficult part where you lay out the compiled binaries (bootloaders, kernel and root filesystem) in the final file that is an SD card image ready to be flashed.

Then, the recipes for the Crystalfontz boards have been added to the meta-fsl-arm-extra layer:

  • First the bootloaders, imx-bootlets and Barebox, including the specific patches and configurations for the Crystalfontz boards.
  • Then the kernel. The linux-cfa recipe uses the 3.10 based kernel available on github.
  • The machine configurations themselves, selecting Barebox as the bootloader and the correct kernel recipe. Also, these are choosing to install the kernel in the root filesystem instead of in its own partition.
  • Touchscreen calibration for the cfa-10057 and the cfa-10058 boards. This is required to get xinput-calibrator working properly as it can’t calibrate without starting values.

In a nut shell, you can now use the following commands to get a working image for your particular Crystalfontz board:

  • For your convenience, Freescale is providing a repo manifest to retrieve all the necessary git repositories. So first download and install repo:
    mkdir ~/bin
    curl https://dl-ssl.google.com/dl/googlesource/git-repo/repo > ~/bin/repo
    chmod a+x ~/bin/repo
    PATH=${PATH}:~/bin
  • We will work in a directory named fsl-community-bsp:
    mkdir fsl-community-bsp
    cd fsl-community-bsp
  • Ask repo to get the master branch, when Yocto 1.5 is released, you could select the new branch. (Edit: starting from September, 28th, you can use the branch named dora)
    repo init -u https://github.com/Freescale/fsl-community-bsp-platform -b master
  • Download the layers:
    repo sync
  • Configure the build for cfa-10036:
    MACHINE=cfa10036 source ./setup-environment build
  • Start the build with:
    bitbake core-image-minimal
  • Grab a cup of coffee!

You’ll end up with an image that you can flash using the following command:
sudo dd if=tmp/deploy/images/cfa10036/core-image-minimal-cfa10036.sdcard of=/dev/mmcblk0

Obviously, you need to replace cfa10036 by the board model you are using in the above commands. While not completely perfect, core-image-sato is also working.

In detail, the contributions from Bootlin are:

Author: Alexandre Belloni

Alexandre is Bootlin's co-owner and COO. Alexandre joined as a kernel and embedded Linux engineer in 2013, and became co-owner and COO in 2021. More details...

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