Guide to adding a new device to an existing family

This documents how to add support for a new device. The running example is the addition of the xc7a100t device to the Artix-7 family.

Adding a new device to an existing family is much simpler than adding a new family, since the building blocks (tiles) are already known. There are just more or fewer of them, arranged differently. No new fuzzers are needed. You just need to rerun some fuzzers for the new device to understand how the tiles are connected to each other and to IOs.

Note: Since this guide was written, the xc7a100t has become the primary device in the database, not a secondary device as it was when it was originally added. Therefore the files currently in the repo don’t match what is described here. But if you look at the original PRs, they match what is described in the examples here.

The main PR from the example is #1313. Followup fixes for problems revealed during testing are #1334 and #1336.

Step 0

Fork a copy of https://github.com/SymbiFlow/prjxray on GitHub (go to the page, click “Fork” button, select your own workspace).

Clone your fork, and make a new branch, with a name related to the new device/package:

git clone git@github.com:<yourUserID>/prjxray.git
cd prjxray
git checkout -b <new_branch_name>

Step 1

Follow the Project X-Ray developer setup instructions in the documentation, up through Step 7 and choose Option 1 (invoke the ./download-latest-db.sh script). This script will clone the official prjxray-db database under database/. The following steps will make changes under this directory. You may want to put these changes on your own fork of prjxray-db for testing. This is explained at the end, under “Database Updates”.

Step 2

Add a new settings file. Usually you will start with an existing settings file and modify it. Assuming you’re in prjxray/,

cp settings/<baseline_device>.sh settings/<new_device>.sh
git add settings/<new_device>.sh

Example:

cp settings/artix7_200t.sh settings/artix7_100t.sh
git add settings/artix7_100t.sh

Update the following values in the new settings file:

  • XRAY_PART – Important: choose a package that is fully bonded (typically the one with the largest number of pins). If the part that you’re actually interested in is different (with fewer bonded pins), it will be handled later. In the running example, the actual part of interest was the xc7a100tcsg324, since that is on the Arty A7-100T board. But here, the xc7a100tfgg676 part is used; the xc7a100tcsg324 is handled later.

  • XRAY_ROI_TILEGRID – modify the bounding boxes to be a tight fit on your new part.

  • XRAY_IOI3_TILES – These tiles need special handling for an irregularity in Xilinx 7-series FPGAs. See the comments in the 005 fuzzer for more information.

This is what the new settings file looked like in the example.

Source this new settings file:

source settings/<new_device>.sh

Step 3

The project needs to know which device is now available and which fabric it uses. Because some devices share the same fabric, this mapping needs to be done manually. Edit the device.yaml file for the used family under settings/<familiy>/device.yaml be adding the device-fabric mapping:

# device to fabric mapping
"xc7a200t":
  fabric: "xc7a200t"
"xc7a100t":
  fabric: "xc7a100t"
"xc7a50t":
  fabric: "xc7a50t"
"xc7a35t":
  fabric: "xc7a50t"

Now, generate all device information for the family:

make db-prepare-artix7

Step 4

Edit the top Makefile

  • Update the Makefile by adding the new device to the correct list, so that the Makefile generates targets for the new device (used in Step 4). <new_device> is the basename of the new settings file that you just created.

<FAMILY>_PARTS=<existing_devices> <new_device>

  • In our running example, we add artix7_100t to ARTIX_PARTS:

ARTIX_PARTS=artix7_200t artix7_100t

Step 5

Make sure you’ve sourced your new device settings file (see the end of step 2) and generated the device information (see the end of set 3). Now it is time to run some fuzzers to figure out how the tiles on your new device are connected.

Make the following target, with <new_device> as above, and setting the parallelism factor -j<n> appropriate for the number of cores your host has. The make job can benefit from large numbers of cores.

make -j<n> MAX_VIVADO_PROCESS=<n> db-part-only-<new_device>

Again, <new_device> must match the base name of the new settings file that was added. For example,

make -j32 MAX_VIVADO_PROCESS=32 db-part-only-artix7_100t

  • It should run fuzzers 000, 001, 005, 072, 073, 074, and 075.

  • 005 will take a long time. Using multiple cores will help.

  • 074 will fail the first time, since it hasn’t been told to ignore certain wires.

    • After it fails, go to the build directory cd fuzzers/074-dump_all/build_<XRAY_PART> (this is the XRAY_PART from the new settings script; in our example, the build directory is fuzzers/074-dump_all/build_xc7a100tfgg676-1/).

    • Run python3 ../analyze_errors.py --output_ignore_list  > new-ignored

    • Inspect and compare new-ignored against existing ignored wire files in ../ignored_wires/.

    • If it looks good, copy it to an appropriately-named file: cp new-ignored ../ignored_wires/artix7/<XRAY_PART>_ignored_wires.txt (in our example, it is ../ignored_wires/artix7/xc7a100tfgg676-1_ignored_wires.txt).

    • Add it: git add ../ignored_wires/artix7/<XRAY_PART>_ignored_wires.txt

  • Return to prjxray/ directory, and clean up 074 to prepare for the rerun: make -C fuzzers/074-dump-all clean

  • Rerun the top make command, e.g. make -j32 MAX_VIVADO_PROCESS=32 db-part-only-artix7_100t

Step 6

The next task is handling the extra parts – those not fully bonded out. These are usually the parts you actually have on the boards you buy.

After the fabric data is generated with step 5, an further target can generate all extra parts for the device.

make -j<n> MAX_VIVADO_PROCESS=<n> db-roi-only-<new_device>

Step 7

Do a spot check.

  • Check that there are new part directories in the database under the family subdirectory, for example:

$ ll database/artix7/xc7a*
xc7a35tftg256-1:
total 48
-rw-rw-r-- 1 daniel daniel  8234 Jan  9 13:01 package_pins.csv
-rw-rw-r-- 1 daniel daniel 18816 Jan  9 13:01 part.json
-rw-rw-r-- 1 daniel daniel 13099 Jan  9 13:01 part.yaml

xc7a50t:
total 15480
-rw-rw-r-- 1 daniel daniel  695523 Jan  9 12:53 node_wires.json
-rw-rw-r-- 1 daniel daniel 8587682 Jan  9 12:53 tileconn.json
-rw-rw-r-- 1 daniel daniel 6562851 Jan  9 10:31 tilegrid.json

xc7a50tfgg484-1:
total 52
-rw-rw-r-- 1 daniel daniel 13056 Jan  9 09:54 package_pins.csv
-rw-rw-r-- 1 daniel daniel 18840 Jan  9 09:58 part.json
-rw-rw-r-- 1 daniel daniel 13099 Jan  9 09:58 part.yaml

Note: These changes/additions under database/ do not get checked in. They are in the prjxray-db repo. This spot check is to make sure that your changes in prjxray will do the right thing when the official database is fully rebuilt. See “Database Updates” below for more information.

Step 8

Assuming everything looks good, commit to your prjxray fork/branch. You should have a new file under settings/, a new ignored_wires file, and a modified Makefile (see the initial PR of the example for reference).

git add Makefile settings/artix7_100t.sh
git status
git commit --signoff

Step 9

Push to GitHub:

git push origin <new_branch_name>

Then make a pull request. Navigate to the GitHub page for your prjxray fork/branch, and click the “New pull request” button. Making the pull request will kick off continuous integration tests. Watch the results and fix any issues.

Database Updates

The process above (steps 4 and 5) will create some new files and modify some existing files under database/, which is a different repo, prjxray-db.

To test these changes before the next official prjxray-db gets built (and even before your PR on prjxray is merged), you can put these changes on your own fork of prjxray-db, and then test them in the context of symbiflow-arch-defs.

To put the db updates on your own fork, create your fork of https://github.com/SymbiFlow/prjxray-db if you haven’t already. Then follow one of the approaches suggested in the checked solution of this StackOverflow post.

You are NEVER going to send a pull request on prjxray-db. The database is always rebuilt from scratch. After your changes on prjxray are merged, they will reflected in the next prjxray-db rebuild. The changes submitted to your prjxray-db fork are only for your own testing.

To use your new repo/branch under symbiflow-arch-defs/third_party/prjxray-db/, you will need to change the submodule reference to point to your fork/branch of prjxray-db.