PCIe Port Configuration via Parallel LTSSM Synchronization
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Solution Overview
Problem
Current PCI Express systems are inefficient in configuring multiple ports simultaneously due to the need to run through the Link Training & Status State Machine (LTSSM) for each port sequentially, which significantly prolongs the configuration time, especially when some state machines take longer than others.
Innovation Solution
The method involves starting multiple LTSSMs in parallel, synchronizing them using timeouts in the detect and polling states, and advancing all to the configuration state only once successful detection or timeouts occur, allowing all ports to be configured in a single pass, with the speed determined by the slowest LTSSM.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple LTSSMs are run sequentially for each port, then configuration reliability is maintained, but configuration time increases significantly
Solution Approach 1:
The patent segments the port configuration process into distinct phases (detect state, polling state, configuration state) that can be executed in parallel across multiple ports. Each LTSSM instance handles one port independently through these segmented phases, allowing simultaneous configuration of multiple ports while maintaining proper sequencing within each phase through synchronization mechanisms.
Solution Approach 2:
The patent merges multiple LTSSM instances to operate simultaneously on different ports rather than sequentially. By combining the resources and capabilities of multiple state machine instances and coordinating them through shared synchronization logic, the system achieves parallel configuration of multiple ports while maintaining the reliability of individual port configuration.
2Productivity
If LTSSMs are run in parallel for all ports simultaneously, then configuration speed improves, but synchronization complexity increases
Solution Approach 1:
The patent divides the parallel configuration process into discrete, manageable phases (detect, polling, configuration) that can be independently controlled and synchronized. This segmentation allows each phase to be managed separately with appropriate synchronization barriers, reducing the overall complexity compared to attempting to coordinate all aspects of parallel configuration simultaneously.
Solution Approach 2:
The patent introduces synchronization mechanisms as intermediary components that coordinate between parallel LTSSM instances. These intermediaries manage the timing and sequencing of state transitions across multiple ports, handling the synchronization complexity in a centralized manner rather than requiring complex point-to-point coordination between all state machines.
3Reliability
If sequential port configuration is used, then resource contention is avoided, but overall system efficiency decreases
Solution Approach 1:
The patent segments resource usage by phase, where resources are allocated and managed independently for each configuration phase across multiple ports. This allows efficient utilization of shared resources during parallel execution while maintaining proper resource management within each segmented phase, avoiding both resource contention and sequential bottlenecks.
Solution Approach 2:
The patent implements dynamic resource allocation where resources are allocated to multiple LTSSM instances based on current configuration needs and availability. The system dynamically adjusts resource distribution across parallel ports while maintaining proper management and coordination, enabling both high efficiency and reliable resource management.
Data Source
AI summary
In a first embodiment of the present invention, a method for configuring a plurality of input/output (I/O) interconnect switch ports is provided, the method comprising: starting a link training and status state machine (LTSSM) for each of the plurality of ports; placing each of the LTSSMs in a receiver detect state; changing all of the LTSSMs to a polling state only once receivers are detected or timeouts occur in the receiver detect states in each of the LTSSMs; changing all of the LTSSMs to a configuration state only once polling is successful or timeouts occur in the polling states in each of the LTSSMs; and completing the configuration state of each of the LTSSMs.