Building a Project

The Mango PetaLinux projects are ready to build as-is. In the project root run petalinux-build. When the build finishes the boot images will be copied to <proj_root>/images/linux and to /tftpboot for retrieval by u-boot via TFTP.

The PetaLinux build system uses caching to speed the build process. Generally petalinux-build will only rebuild components that have changed since the previous build. For example, to iterate on the mango_wlan driver module, edit the source in components/meta-mango/recipes-kernel/mango-wlan, then re-run petalinux-build to compile the updated module. The build flow always regenerates the boot images and copies them to /tftpboot.

The petalinux-build command has many optional arguments. For example petalinux-build -c mango_wlan -x do_devshell will launch a new shell in the mango_wlan build folder with the complete cross-compilation environment setup. Refer to the PetaLinux documentation for more details.

Booting the Mango PetaLinux reference project requires BOOT.BIN and image.ub images. The project includes pre-built images in <proj_root>/images/linux which can be used as-is.

The sections below describe the contents of these images and how to generate these images after making changes to the reference project.

Required Binaries

Booting Linux on an MPSoC device requires the following binaries:

  • PMU Firmware
  • ARM Trusted Firmware (bl31)
  • First Stage Bootloader (FSBL)
  • Second stage bootloader (u-boot)
  • RPU applications
  • Device tree blob
  • Linux kernel image
  • RAM filesystem

The Mango reference PetaLinux projects can generate all of these binaries, and the PetaLinux tools can package the binaries into a few archives that simplify the boot process.

BOOT.BIN

The first boot archive is BOOT.BIN which bundles:

  • PMU Firmware
  • ARM Trusted Firmware (bl31)
  • First Stage Bootloader (FSBL)
  • Second stage bootloader (u-boot)

The BOOT.BIN file must be copied to a FAT-formatted SD card. Mango provides a pre-built BOOT.BIN with the reference design.

The BOOT.BIN file must be updated any time the FSBL or u-boot changes in the PetaLinux project. Typically this only occurs for changes to the PS/PL configuration in the Vivado FPGA design. For software-only changes or FPGA design changes which do not modify the PS configuration, there is no need to update BOOT.BIN.

To generate BOOT.BIN from a PetaLinux project, run petalinux-package --boot --u-boot --pmufw --force, confirm output:

Find BOOT.BIN in <proj_root>/images/linux/.

The Xilinx tools support bundling the FPGA bitstream into BOOT.BIN via the petalinux-package --fpga option. Mango recommends not including the bitstream here, instead configuring the PL from Linux userspace after the node has booted. This simplifies iterating on the FPGA design.

image.ub

The second boot archive is a FIT image containing:

  • Device tree blob
  • Linux kernel image
  • RAM filesystem

Mango provides a pre-built image.ub with the reference design. The image.ub image can be loaded via the SD card or via TFTP.

This image is automatically generated by petalinux-build after any software or hardware changes. Find the newly built image.ub in <proj_root>/images/linux/. PetaLinux also copies image.ub to /tftpboot for loading via TFTP.

FPGA Bitstream

The programmable logic (PL) section of the Xilinx device is configured with a bitstream. The bitstream is generated by the Vivado hardware synthesis/implementation tools. The Mango PetaLinux projects include a prebuilt bitstream that can be used without re-running the Vivado flow. By default the bitstream is included in the root filesystem at /usr/share/mango_wlan/mango_wlan_<version>.bit. The same bitstream is stored in the PetaLinux project at <proj_root>/project-spec/hw-description/system.bit.

The FPGA bitstream is loaded into the PL at runtime from Linux userspace using the Xilinx fpga_manager framework:

If you re-run the hardware tools to generate a new bitstream it is necessary to copy the updated bitstream to the node via the SD card, NFS or SFTP.

RPU Applications

The MAC software runs in the two ARM R5 CPUs in the MPSoC RPU. One elf binary must be provided for each CPU. For normal 802.11 applications CPU R5_0 runs the high_linux_dev application and CPU R5_1 runs low_dcf application.

Prebuilt elf binaries are provided in the PetaLinux reference projects. These reference binaries are copied to /lib/firmware in the root filesystem by default (see Booting).

Custom binaries can be built via the Xilinx SDK. Refer to the “MAC Software Workspace” section above for creating the SDK Workspace and compiling the applications. In the SDK workspace the elf binaries are located at components/wlan_mac_workspace/wlan-sdk/projects/<app>/Debug/<app>.elf for each MAC application.