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Integration of FPGA bitstreams into Yocto system

The handling of FPGA bitstreams and derivation of bin files & device trees is complex and spread across different layers and recipes.

There are two use cases - either to use HDF_PATH and define a single .xsa file to be included in the Yocto image, or to define PL_VARIANTS_DIR and PL_VARIANTS and use multiple .xsa files to be bundled in the image along with their respective device tree overlays.

Global variables

These have to be defined at a central place visible to all other recipes; e.g. local.conf or the application's layer.conf.

  • PL_SUFFIX: Defines an (optional) suffix for the package names of the programmable logic related packages such as external-hdf, bitstream-extraction etc. This makes it possible to assign a project name to the packages, and to avoid name collisions in a shared package feed. Example:

    PL_PKG_SUFFIX = "-example-design"

    The PL-related packages will then be named external-hdf-example-design(..).rpm, bitstream-extraction-example-design(..).rpm, etc.

  • PL_VARIANTS: Defines a set of basenames of .xsa files to be bundled into the root filesystem. Example:

    PL_VARIANTS_damc-fmc2zup = "zu11eg zu19eg"

    The build system will then use the basename and for each variant try to find a file such as zu11eg.xsa, zu11eg-1.2.3.xsa or zu11eg-1.2.3-4-g12345678.xsa.

external-hdf

  • meta-xilinx-tools/recipes-bsp/hdf/external-hdf.bb

    • Acquires the hardware description .xsa declared by HDF_PATH or PL_VARIANTS_DEFAULT in the downstream recipe & installs it to /opt/xilinx/hw-design/design.xsa.
    • Deploys the .xsa to ${DEPLOYDIR}/Xilinx-${MACHINE}.xsa.

  • meta-techlab-utils/recipes-bsp/hdf/external-hdf.bbappend

    • Acquires and deploys .xsa files when PL_VARIANTS_DIR is set, or falls back to HDF_PATH, which must be an absolute path unless the file is provided in a further overlay. When HDF_PATH contains an asterisk (*), the glob result with the latest modification time is selected.
    • Sets a default variant as defined in PL_VARIANTS_DEFAULT. If PL_VARIANTS_DEFAULT is not set, it uses the first PL_VARIANT as default one.
    • Picks up version suffixes in filenames such as zu11eg-1.2.3.xsa or zu11eg-1.2.3-45-g12345678.xsa.

  • meta-<application>/.../hdf/external-hdf.bbappend

    • Defines HDF_PATH or PL_VARIANTS_DIR, PL_VARIANTS_DEFAULT and provides .xsa files.

device-tree-from-bd

  • meta-techlab-utils/recipes-bsp/device-tree-from-bd/device-tree-from-bd.bb
    • Creates a app_from_bd.dts for the .xsa in HDF_PATH or PL_VARIANTS_DEFAULT.
    • When PL_VARIANTS is set, it also iterates through all .xsa files provided by external-hdf and creates a app_from_bd_<variant>.dts for each.

device-tree

  • meta-techlab-bsp/recipes-bsp/device-tree/device-tree.bbappend
    • Adds on-board (system) peripherals, defined in board-specific system-user.dtsi, to system-top.dts.
    • Adds BSP related information (drivers etc) for PL, defined in board-specific pl-conf.dtsi, to pl.dtsi.
    • When PL_VARIANTS is set, it iterates through app_from_bd_<variant>.dts for all variants and for each one, merges it with the other PL related files to pl-var-<variant>.dtsi.
    • Upstream device-tree.bb will create a pl-var-<variant>.dtbo for each of them.

bitstream-extraction

  • meta-xilinx-tools/recipes-bsp/bitstream/bitstream-extraction_git.bb

    • Extracts .bit file from .xsa file.

  • meta-techlab-utils/recipes-bsp/device-tree-from-bd/bitstream-extraction_git.bbappend

    • Also extracts bitfiles from all variants declared in PL_VARIANTS.

fpga-manager-util

  • meta-xilinx-tools/recipes-bsp/fpga-manager-util/fpga-manager-util_1.0.bb

    • Generates binfile from bitfile.
    • Installs binfile & device tree overlay .dtbo to /lib/firmware/... on rootfs.

  • meta-techlab-utils/recipes-bsp/device-tree-from-bd/fpga-manager-util_%.bbappend

    • Also creates binfiles and installs binfiles & device tree overlays for all PL_VARIANTS.

fpgautil-init

  • meta-techlab-bsp/recipes-bsp/fpgautil-init/fpgautil-init.bb
    • Installs init script which downloads the appropriate bitstream into the FPGA & installs the appropriate device tree overlay in the Linux system.