Customize device tree

Note: The following instructions describe device tree modification for the MistySOM CARRIER and need to be customized to fit a different hardware platform.

dev shell

Start the build container with the -n switch to launch a MistySOM development shell and follow the instructions to build a fresh copy of images.

After the build has completed, the device tree source file is located at tmp/work-shared/smarc-rzv2l/kernel-source/arch/arm64/boot/dts/renesas/r9a07g054l2-smarc.dts inside the build/ directory. it includes multiple "device tree include" files (*.dtsi):

#include "r9a07g054l2.dtsi"
#include "rzg2l-smarc-som.dtsi"
#include "rzg2l-smarc-pinfunction.dtsi"
#include "rz-smarc-common.dtsi"
#include "rzg2l-smarc.dtsi"

To update the pin assignments, rzg2l-smarc-pinfunction.dtsi needs to be patched.

  1. Create a temporary work directory with: $ mkdir ~/tmp
  2. Copy the device tree file that is going to be patched and copy it to ~/tmp:
    $ cp ./build/tmp/work-shared/smarc-rzv2l/kernel-source/arch/arm64/boot/dts/renesas/rzg2l-smarc-pinfunction.dtsi ~/tmp/
  3. Change to the directory $ cd ~/tmp
  4. Create a copy of the just copied device tree include file: $ cp rzg2l-smarc-pinfunction.dtsi rzg2l-smarc-pinfunction.dtsi.orig
  5. Modify the originally copied file in your favourite editor: $ vim rzg2l-smarc-pinfunction.dtsi
  6. Create patch with $ git diff --no-index rzg2l-smarc-pinfunction.dtsi.orig rzg2l-smarc-pinfunction.dtsi > 0001-mistysom-pin-updates.patch
  7. view the patch file $ vim 000-mistysom-pin-updates.patch to confirm the changes
  8. update the a and b filenames on the top of the file (to indicate the correct paths)
  9. Change the paths from:
--- a/rzg2l-smarc-pinfunction.dtsi.orig
+++ b/rzg2l-smarc-pinfunction.dtsi


--- a/arch/arm64/boot/dts/renesas/rzg2l-smarc-pinfunction.dtsi
+++ b/arch/arm64/boot/dts/renesas/rzg2l-smarc-pinfunction.dtsi
  1. Add a custom Yocto Layer that applies the patch to the build
  2. Copy the patch to the custom layer (called meta-mistysom in this example)
    • Return back into the build directory $ cd ~/rzv_vlp_v3.0.0/
    • Source the environment (just in case $ source poky/oe-init-build-env)
    • Leave the build/ directory $ cd ..
    • Create a recipe dir $ mkdir -p meta-mistysom
    • Change into the newly created directory $ cd meta-mistysom
    • Create a kernel-patch dir $ mkdir -p recipes-kernel/linux/
    • Copy the patch file into the newly created dir $ cp ~/tmp/0001-example.patch recipes-kernel/linux/
    • Lookup kernel name $ oe-pkgdata-util lookup-recipe kernel
      expected result linux-renesas
    • Create append file with kernel name (for any kernel version) $ vim recipes-kernel/linux/linux-renesas_%.bbappend