Wednesday, August 30, 2017

Happy sixth birthday FuseSoC

Today FuseSoC is turning six years old. That is probably something like 35 in software years. It has had a colourful past with some breakups and an identity crisis, but has now settled down and realized that it will not change the world in the same way that it used to think. It has spawned a few child projects which are not yet able to handle themselves in the world and still need their loving parent project. Being 35 also means that we can expect a FuseSoC middle-age crisis in a few years where it will try to reinvent itself in a desperate attempt to appear youthful. All in all, it's pretty similar to it's author.

As with most software, there is no birth certificate, but we will use the date of the first commit to the repo of what would become FuseSoC as the birth date. So what really happened on that fateful day that would become forever etched into history as the day when everything changed? According to Wikipedia, it wasn't a happy day overall, but none of those events are really related to FuseSoC.

As so often, we need to go back further in time and take a look at the events leading up to this day. It all started with the OpenRISC Reference Platform System on Chip version 2, or ORPSoCv2. This project was a combination of RTL code for the OpenRISC CPU together with a bunch of peripheral controller cores, drivers, example applications and miles of makefiles to build everything together into FPGA images that could be loaded onto a few select boards for running OpenRISC-based systems. Despite having one of the least sexy names ever, it was widely used by most people who dealt with OpenRISC and seems to still be in use by some people.  But it wasn't without flaws. Due to the tightly integrated nature of the project, everyone who wanted to add support for a new FPGA board or add some extra peripheral driver ended up with their own version of the project, each with their own bugs and features. Fixes were rarely submitted back upstream to the main ORPSoCv2 repo. Also, the RTL code for the CPU and peripheral controllers were copies of other repositories, which quickly started to diverge from their upstream counterparts. Again, none of that code was submitted upstream. There were also other issues with regards to scalability that started to show when more features were added. In short, it was time for something new.

I started sketching out what I would like to see in a successor, and then started implementing ORPSoCv3. Just like ORPSoCv2 this was a system of makefiles calling into other makefiles, but with a major difference. Instead of storing copies of cores, the upstream versions were fetched when they were requested in a SoC to avoid all the code duplication. After some time, I was ready to present my work in progress to the world. At that time I was working for the company that owned and maintained OpenCores. The git hype had already started to sweep through the software landscape and I had been trying to convince my co-workers that we needed to start making OpenCores support git instead of just SVN. I never managed to convince them, but at least I got them to set up a git server where I could put my project as a trial. Except for three or four outdated clones of other OpenRISC-related projects, I had the only git repo at the now defunct On August 30 20111 I made the first commit.

The better part of the coming year was spent on writing makefiles calling other makefile until one day I had enough and decided that I will never in my life write another makefile calling other makefiles. It was time to kill my darling. I started a new implementation in Python with the lessons learned and soon got to a state where I wanted to present it to the world. As I only had this one git repo and no real understanding of git work flows, my instinct was to clean out the old repo and just push the new code in. Unfortunately I never figured out how to get rid of the first commit, which resulted in this sequence of commits:

Even after the Python migration, FuseSoC (or ORPSoCv3 really) was still storing a lot of RTL code in the repo. It was a shaky relationship, and in August 2013 there was an inevitable separation of tool and RTL code. The RTL code went into a new project called orpsoc-cores. There wasn't any crying involved an both parties realized that it was best to go separate ways. A day later, the first released version, ORPSoC 3.0 was released.

Life went on, new features were added, bugs were fixed, ORPSoCv3 became older and fatter, but it became more and more evident that ORPSoC really didn't have anything to do with OpenRISC. Everything that was OpenRISC-specific had already moved to the orpsoc-cores repository and ORPSoCv3 was really a dependency manager and build system for any RTL code. It was once again time to cut some ties. As usual, names are harder than code, and I spent some time trying to figure out what to call the thing I had created. One of the main alternatives was SoCify, but it turned out someone else had already used that name. In hindsight, I'm really grateful for that. SoCify as it is a horrible name. The idea of FuseSoC came from the analogy of fusion reactions to build something bigger from a number of smaller cores. The minimalist in me also considered FuSoC, which is also pretty bad and sounds a bit like F*** you SoC. I do like FuseSoC though. In February 2014 the big rename was made, the project was moved to its current location and FuseSoC 1.0 was released.

Since then not much has happened. New features are added. Bugs are fixed, reintroduced and fixed again. FuseSoC is getting older and fatter. I'm really grateful for all help that I have received over the years. According to github, there have been 20 contributors to the code base, but there are also a number of other people who have submitted bugs or contributed to the RTL code in the standard core library. Big thanks to everyone involved.

Birthdays usually involve presents. But what can we give to a project that already has everything? How about a logo and a home page? That's the perfect gift for a six year old and on this big day I can proudly announce the brand new home page (Ssshhh...I have had the domain name since 2014, but don't tell FuseSoC) and the FuseSoC logo.

Happy birthday FuseSoC! I will now leave the word to the millions of users to tell their stories of how FuseSoC has changed their lives.

No comments:

Post a Comment