Build SOF with Zephyr

This guide describes how to build and run Sound Open Firmware as a Zephyr application.

Note

The following example uses $ZEPHYR_WORKSPACE as the working directory.

Prepare

The easiest way to build Zephyr is to use its recommended toolchain. Follow instructions in Install a Toolchain for details.

Check out and build

  1. Install west. Zephyr uses west as a source management and building system. Follow the Zephyr Getting Started guide for dependencies and for the west installation.

    Note

    If you need a different SOF version than the one that west automatically checks out, change to modules/audio/sof and use git to select your preferred version. You need at least version 1.6 to use it with Zephyr. Make sure you branch or tag your code in git; otherwise, a future west update may lose it. See the west user guide.

  2. Initialize a new west repository. This checks out all Zephyr sources, including SOF:

    mkdir $ZEPHYR_WORKSPACE
cd $ZEPHYR_WORKSPACE
west init
# Significantly smaller and faster than a full "west update"
west update hal_xtensa sof

  3. Build and sign a firmware image:

    cd $ZEPHYR_WORKSPACE
./modules/audio/sof/scripts/xtensa-build-zephyr.sh -h  # shows usage
./modules/audio/sof/scripts/xtensa-build-zephyr.sh $your_platforms
ls build-*/zephyr/zephyr.*
  => build-*/zephyr/zephyr.ri ...

  4. Fetch and switch to the latest SOF code

    By policy, zephyr modules are carefully versioned with west and not automatically synchronized with the latest code. To switch to the latest:

    cd modules/audio/sof/
git remote add sof https://github.com/thesofproject/sof
git fetch sof
git switch --track sof/main

    You can also delete the sof clone downloaded by west and replace it with an older clone; west will automatically adjust.

Run

For convenience, the xtensa-build-zephyr.sh script copies all firmware files into a single, “staging” directory:

$ tree build-sof-staging/

build-sof-staging/
├── sof
│   ├── community
│   │   ├── sof-apl.ri
│   │   ├── sof-imx8.ri
│   │   └── sof-tgl-h.ri

  1. Copy the firmware image(s) to the usual location on all your target systems. Example:

    sudo rsync -a build-sof-staging/sof/ testsystemN.local:/lib/firmware/intel/sof/

    rsync also works locally and unlike cp -R it is always idempotent. You may want to use the rsync -a --delete option to make absolutely sure you’re not running some older version but only after backing up your original sof/ directory first. The --delete option is dangerous, use it only in very well tested scripts.

    Also make sure nothing in /lib/firmware/updates takes precedence, see https://www.kernel.org/doc/html/v5.5/driver-api/firmware/fw_search_path.html

  2. Reboot the system. Note that the location and name of your SOF firmware image may vary by system. Search your kernel logs with journalctl -k -g sof, looking for a line such as the following to identify which file under /lib/firmware/ your hardware is using:

    sof-audio-pci 0000:00:0e.0: request_firmware intel/sof/community/sof-apl.ri successful

  3. Verify that the new firmware is being used by running the following:

    dmesg | grep zephyr

    You should see a line such as the following:

    sof-audio-pci 0000:00:0e.0: Firmware info: used compiler GCC 9:2:0 zephyr used optimization flags -Os

For firmware log extraction, use zephyr/boards/xtensa/intel_adsp_cavs15/tools/README.md.

You might also need to build and update your system audio topology file. For details see Build SOF from scratch.