The boot image for the Versal ACAP is called a PDI, which is a Xilinx file format processed by the PLM as part of the Versal ACAP boot process or partial configuration process. The PDI data is specific to the design requirements. The Versal ACAP boot image typically involves binaries used to boot and configure the platform, these binaries can include: bootloader, firmware, hardware configuration data, OS and user applications. Examples include adaptable engine (PL) configuration file, PLM image, TF-A, U-Boot, Linux kernels, rootfs, device tree, and standalone or RTOS applications.
A PDI file is a collection of images, where an image consists of one or more partitions. A partition can include:
- CDO file consisting of a list of commands executed in sequence
- Loadable data ( for example, APU/RPU ELFs or data)
There can be different PDI files based on the use case.
- PDI for Versal ACAP Start-up
- Occurs during the power-on reset (POR) and SRST. This PDI contains the
following information needed to boot, configure, and manage a Versal ACAP:
- A boot header
- A PLM subsystem
- Additional subsystem images and image partitions which are used to configure a specific subsystem or engine. These can also include necessary CDO. Some of these images can also be part of another PDI that is targeted for secondary boot.
- PDI for Subsystem Restart or DFX
- Occurs in some power management, warm restart, PL reconfiguration, and DFX
This type of PDI contains the images or partitions needed to reconfigure parts or subsystems of the Versal ACAP, and does not contain the boot header, PLM, and the PMC.CDO.