Remote Control: A Simple Deadlock Avoidance Scheme for Modular System on Chip

Abstract: The increase in design cost and complexity have motivated designers to adopt modular design of System on Chip (SoC) by integrating independently designed small chiplets. However, it introduces new challenges for correctness validation, increasing chances of forming deadlock in the system involving multiple chiplets. Although there have been many solutions available for deadlock freedom in flat networks, the study on deadlock issue in chiplet-based systems is still in its infancy. A recent study suggests adding extra turn restrictions as a viable solution for this problem. However, imposing extra turn restrictions reduces chiplet design flexibility and interposer design complexity. In addition, it may lead to non-minimal route and traffic imbalance forming hotspots, resulting in high latency and low throughput. We propose Remote Control (RC), a simple routing oblivious deadlock avoidance scheme. Our proposal is based on two key observations. First, packets with destinations in the current chiplet are blocked by packets with destinations outside the chiplet. Second, deadlock always involves multiple boundary routers. Hence, we segregate different traffics to alleviate mutual blocking at the chiplet's boundary routers. Along with guarantee of deadlock freedom and performance enhancements, our simple RC scheme also provides more routing flexibility to both chiplet and SoC designers, as compared to the state-of-the-art.