SoC Bandwidth Control for Arbitration Saturation
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Solution Overview
Problem
In multi-master system-on-chip environments, particularly in safety-critical fields like automotive and aeronautics, saturation problems arise due to contention when accessing slow peripherals, leading to uncontrolled process execution times and loss of determinism, which existing methods address by increasing contention percentage, thereby reducing system performance.
Innovation Solution
The system-on-chip incorporates control means to manage bandwidth for each slave resource based on its processing capacity and allocates request processing capacity among master resources, using FIFO buffer memories and hierarchical arbitration levels to prevent saturation by controlling request transmission and defining maximum transmission rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multi-master resources access peripherals through hierarchical arbitration levels, then system flexibility and resource sharing are improved, but arbitration level saturation occurs leading to loss of determinism
Solution Approach 1:
The patent applies preliminary action by calculating and storing the maximum propagation time for each peripheral before the system operates. This pre-computed timing information is stored in a lookup table, allowing the arbitration system to determine worst-case scenarios in advance without requiring real-time analysis, thus maintaining determinism while enabling flexible resource sharing.
Solution Approach 2:
The patent introduces an intermediary mechanism in the form of a bandwidth control unit that mediates between master resources and peripherals. This unit monitors and regulates the access requests, ensuring that no single master resource can saturate the arbitration levels, thereby preventing loss of determinism while maintaining system flexibility.
2Reliability
If contention percentage is increased to resolve saturation problems, then determinism is maintained, but system performance is degraded
Solution Approach 1:
The patent implements feedback by continuously monitoring the actual propagation times of data through the arbitration levels and comparing them against the pre-calculated maximum values. When the system operates within expected parameters, no corrective action is needed, maintaining high performance. The feedback mechanism only activates corrective measures when actual timing approaches the pre-determined limits, thus maintaining determinism without unnecessarily degrading performance.
Solution Approach 2:
The patent changes parameters dynamically by adjusting the bandwidth allocation and arbitration priorities based on real-time system conditions. Instead of using a fixed high contention percentage, the system adapts parameters such as request timing and resource allocation to maintain determinism only when necessary, thereby preserving overall system performance.
3Reliability
If exhaustive characterization is performed for the entire usage domain, then determinism can be guaranteed, but system complexity and configuration time increase
Solution Approach 1:
The patent applies segmentation by dividing the usage domain into distinct operational scenarios or profiles. Instead of characterizing the entire usage domain exhaustively, the system segments it into manageable parts, each with its own pre-calculated maximum propagation times. This reduces the complexity of configuration while still providing deterministic guarantees for each segment.
Solution Approach 2:
The patent uses partial action by performing characterization only for the most critical peripherals and usage scenarios rather than exhaustively characterizing all possible cases. The pre-computation focuses on the subset of peripherals that have the greatest impact on system determinism, reducing configuration complexity while maintaining adequate determinism guarantees for critical operations.
Data Source
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AI summary
This system-on-a-chip (10) comprises a plurality of master resources, a plurality of slave resources, and a plurality of arbitration levels (A1,...,AN). Each arbitration level (A1,...,AN) is capable of controlling access from at least one master resource to at least one slave resource. Each master resource is capable of sending requests to at least one slave resource according to a bandwidth associated with that slave resource and that master resource. The system (10) is further characterized in that it comprises control means (20) configured to control each bandwidth associated with each slave resource based on the capacity of that slave resource to process requests from the master resource corresponding to that bandwidth.