A Deadlock-Free Bridge Module for Inter-Chiplet Cache-Coherent Communication in an Open Chiplet Ecosystem

The envisioned open chiplet ecosystem promises significant reductions in chip design complexity and cost by enabling designers to rapidly assemble standard chiplets from diverse vendors. Constructing such an open chiplet ecosystem requires support from Network-on-Chip (NoC) routing algorithms, as integrating multiple chiplets onto an interposer can potentially lead to inter-chiplet deadlock. Prior work avoids deadlock through methods like turn restrictions, virtual channel isolation, or packet injection control, or recovers from deadlock using mechanisms such as escape channels or bubble flow control. These approaches achieve a favorable balance regarding modularity, performance, and cost. However, they still rely on designers possessing detailed knowledge of the internal NoC architecture within each chiplet. This requirement impedes the development of a truly open ecosystem, as it constrains chiplet interoperability and vendor independence. Addressing this limitation, we propose a Deadlock-Free Bridge Module (DFBM) designed to resolve interchiplet deadlock without relying on the specifics of individual chiplet NoC implementations. The DFBM infers the transmission behavior of inter-chiplet packets by analyzing the dependency relationships among coherence protocol transaction flows. It then employs a packet injection control mechanism to isolate inter- and intra-chiplet packets, thereby preventing deadlock. DFBMs can be seamlessly interconnected between arbitrary chiplets to achieve deadlock-freedom, eliminating the need for modifications to their internal NoC architectures. Experimental results demonstrate that DFBM incurs only 2.5% area overhead, while achieving a performance improvement ranging from 1% to 7%.