3.7 KiB
The Plan/Roadmap for ROSE
Plans turn fear into focus, risk into reach, and steps into a path.
This plan has been modified in the course of the development of ROSE. And that was also in the plan itself: you plan at every step. See the end for the changes made to the plan.
The roadmap
This is a rough summary of what I did and what I plan to do.
[DONE] Learning RTL and HDL and getting familiar with SPI
Implement a functional SPI slave on the FPGA. Add small logic to manipulate the data. Learn about cross-clock domain design and implementation.
[TODO] Implement the routing logic along with the interfaces
This would be the core part of implementing ROSE on the fabric side. This is a bare minimum implementation disregarding any congestion control or inter-fabric routing.
[TODO] Test on a RPi-FPGA setup
Getting the code to run on sims is one thing, getting it to run on actual hardware is another. This entire step will be to ship the code onto my setup and deal with any kind of synthesis and place-and-route problems that sims won't reveal.
[TODO] Implement logging to an external device via UART
This would lay the foundations for THORN and PETAL and also would come in handy when analyzing congestion and other anomalies.
[TODO] Test on a RPi-FPGA-RPi setup
This is where THORN would branch off from ROSE. ROSE should keep some minimal unit test testbenches, and have fully functional test suites and toolchains be implemented in THORN.
[TODO] RPi's ROSE buffer implementation
mmap memory for the SPI drivers on RPi's to simulate zero-copy on
the RPi's.
[TODO] Modify the SPI kernel drivers for explicit DMA control
Allow ROSE's DMA to be implemented in the drivers.
[TODO] Abstract ROSE into APIs or kernel devices
Note: This may be implemented as development of THORN goes into action, or be facilitated by it.
[TODO] Implement congestion control
When the logic for the fabric is mature enough, it should be upgraded.
[TODO] Implement mesh networks allowing inter-fabric routing
ROSE shouldn't be limited to only 1 fabric.
Changes to the plan
The plan is always changing, but it's important to remember what I learned from every change.
Ditching dynamic routing
In a datacenter or HFT setup, it's rarely expected that the connected devices will change. Hardcoded routing paths is very acceptable and keeps up with the deterministic nature of ROSE.
The lesson learned
Figure out the exact target of ROSE - it's not meant for generic networks, so shave off any redundancy that it doesn't need.
Not reversing the input when testing out the SPI interface
A few things to note:
- Sending the bytes incremented by 1 back is sufficient to prove a stable connection.
- Reversing the input would result in a double-ended queue and increasing the complexity of the logic without little benefits to later steps.
So, I've decided to ditch this idea.
The lesson learned
Plan with the next step in mind, take actions with the next step in mind. Know what is enough and what is too far.
Moving deployment onto the hardware until later on
Originally, I planned to deploy the logic and test with real hardware as soon as I have a working SPI module. But that's not really applicable. I'd be fixing the synthesis with every step thereafter. Better to finalize the design in sims first, and then solve the FPGA-specific problems as an entire step.
I'd rather scratch my head over a bunch of problems at once than to scratch my head every time I push an update to the logic.
The lesson learned
Weight testing against the cost of time and efficiency. If testing hinders development, then it should be separated from the development cycle.