AN 798: Partial Reconfiguration with the Arria 10 HPS

ID 683034
Date 1/25/2017
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Document Table of Contents
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Overview of Software Image Creation

The SoC FPGA GSRD provided on rocketboards.org is not initially set up for PR. The Linux kernel is compiled with the required configuration options for PR, and the preferred command line tool for managing device tree overlays is provided, but the device tree loaded at boot (the “live tree”) is not laid out properly for PR.

The Linux kernel build configuration options required for PR are shown in the following list. These options must be set in the socfpga_defconfig file when rebuilding the Linux kernel as described on rocketboards.org. The Linux kernel provided with the GSRD was built with these options enabled.

CONFIG_FPGA=y
CONFIG_FPGA_REGION=y
CONFIG_FPGA_MGR_SOCFPGA=y
CONFIG_FPGA_MGR_SOCFPGA_A10=y
CONFIG_FPGA_BRIDGE=y
CONFIG_SOCFPGA_FPGA_BRIDGE=y
CONFIG_ALTERA_FREEZE_BRIGE=y
CONFIG_OF=y
CONFIG_OF_OVERLAY=y
CONFIG_OF_CONFIGFS=y
CONFIG_CONFIGFS_FS=y

The command line tool used to manage device tree overlays is called dtbt, an open source Python script. The source code is provided at altera-opensource/dtbt on GitHub. The software tool is provided in the /sbin/ directory of the GSRD SD card image. Use dtbt -h for more information.

The default device tree provided with the GSRD is not set up for PR. To support PR, the device tree loaded at boot must contain a definition of the FPGA regions linking the HPS FPGA manager and the bridge controllers to the top level FPGA region. The default tree provided on the GSRD SD card image from rocketboards.org does not provide this linkage.

After a proper device tree is loaded at Linux boot time, the dtbt tool is used to load and unload device tree overlays to modify the live tree.

The instructions provided in this document describe how to build a minimal boot device tree to support PR. Instructions are also provided on how to build the required device tree overlays, where to place them within the Linux directory structure on the SD card, and how to load and unload them using the dtbt command line tool.

To create and run the software image, you carry out these steps:

  1. Rebuild the Linux kernel with build configuration options for PR
  2. Create a Linux device tree describing the FPGA manager and the bridge controllers in relation to the top-level configuration region
  3. Create device tree overlays for personas in each PR region
  4. Place the device trees in the correct location in the Linux directory structure
  5. Boot the Linux system, loading the default device tree and the base revision overlay
  6. Use the dtbt tool to load and unload device tree overlays for various personas