PCIe Link State Negotiation for Synchronized Merging
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Solution Overview
Problem
In PCI Express systems, determining the downstream configuration of a PCI-E upstream device is challenging due to unknown link configurations during initialization, leading to inconsistent state transitions and potential failures in merging links for data transmission.
Innovation Solution
A state negotiation method where the state of a second link is detected when a first link is ready to change states, and both links negotiate to enter the new state simultaneously if the second link is in the same state within a specified duration, using a judge window to determine if links are comparable for merging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the downstream configuration is determined according to multiple independent links during initialization, then the PCI-E upstream device can support flexible multi-connecting configurations, but inconsistent state transitions occur between links leading to potential failures in merging links for data transmission
Solution Approach 1:
The patent applies preliminary action by detecting the state of a second link before the first link transitions states. A state detection mechanism monitors whether the second link is in the same state within a specified duration before allowing state transition, ensuring links are synchronized beforehand to prevent inconsistent state transitions during merging operations
Solution Approach 2:
The patent implements feedback through a state detection and comparison mechanism. The system continuously monitors the states of multiple links, compares them within a specified duration window, and uses this feedback information to control state transitions, ensuring that links only transition when their states are consistent, thereby maintaining reliability during flexible configurations
2Productivity
If state transitions are performed independently on each link without coordination, then the initialization process is simpler and faster, but packet transmission inconsistencies occur when links are intended to be merged
Solution Approach 1:
The system performs preliminary state detection and comparison before executing state transitions. By checking whether links are in the same state within a specified duration before transitioning, the system ensures synchronization is established in advance, preventing packet transmission inconsistencies while maintaining efficient initialization
Solution Approach 2:
The patent introduces dynamic state coordination where the state transition timing of links is adjusted based on real-time state detection. The system dynamically controls when links transition states by monitoring their current states and only allowing transitions when consistency is detected, creating an adaptive synchronization mechanism that maintains both speed and reliability
Data Source
AI summary
In a state negotiation method of a PCI-E upstream device supporting multiple downstream configurations, a state of a second link asserted by a second state machine of the PCI-E upstream device is detected when a first link asserted by a first state machine of the PCI-E upstream device is ready to change from a first state to a second state in a specified duration. A negotiating procedure is performed to have the first link and the second link enter the second state simultaneously if the second link is detected to be in the first state within the specified duration.