Multi-Port Firewall Isolation for DMA-Safe Port Resets
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Solution Overview
Problem
Conventional resets on communication ports in a multi-port system disrupt data transmission and cause a hang condition in the Direct Memory Access (DMA) system, affecting all connected ports and requiring a system reset, which further disrupts communication.
Innovation Solution
Implementing firewall circuits in each port to monitor for reset conditions and enter a firewall operating mode, isolating the affected port from the DMA system, allowing it to continue operating without disrupting other ports by responding to client circuits on behalf of the host system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional reset is performed on a communication port, then the PCIe link on that port is brought down to stop data transmission, but the DMA system enters a hang condition and becomes unresponsive, disrupting all communication ports
Solution Approach 1:
The patent divides the system into isolated segments by introducing firewall circuits between each PCIe controller and the DMA system. When a reset occurs on one port, the firewall circuit isolates only that specific controller from the DMA system, preventing the hang condition from propagating to other ports. This segmentation allows independent failure containment without requiring system-wide resets.
Solution Approach 2:
The firewall circuit acts as an intermediary component between the PCIe controllers and the DMA system. It monitors reset conditions and selectively blocks communication from affected controllers while allowing other controllers to continue operating normally. This intermediary prevents the harmful propagation of reset conditions without disrupting overall system functionality.
2Ease of operation
If the DMA system is reset to restore operation after a port reset, then communication on the affected port can resume, but communication on other unaffected ports is also disrupted
Solution Approach 1:
By segmenting the connection between PCIe controllers and the DMA system through firewall circuits, the patent enables selective isolation of affected ports. This allows the DMA system to continue processing transactions from unaffected controllers without being reset, thereby maintaining overall system productivity while restoring the affected port.
Solution Approach 2:
Instead of performing a complete system reset, the firewall circuit implements a partial reset by isolating only the specific controller experiencing the hang condition. This partial action restores the affected port while leaving the rest of the system operational, avoiding the excessive disruption caused by a full system reset.
3Reliability
If a reset occurs in the middle of data transmission, then the PCIe link stops sending/receiving data, but requests and responses are lost and data backs up in the DMA system
Solution Approach 1:
The firewall circuit serves as an intermediary that detects reset conditions and blocks backup data from entering the affected controller's communication path. This prevents data loss and backup issues by stopping the flow of data at the firewall boundary when a reset is detected, while allowing the DMA system to continue operating with other controllers.
Data Source
AI summary
Handling port resets in a multi-port system includes monitoring, using a plurality of firewall circuits, a plurality of controllers corresponding to different communication ports for a reset condition. The plurality of controllers are coupled to a direct memory access (DMA) system through a plurality of bridge circuits. A selected firewall circuit detects a reset condition on a selected controller coupled thereto. The selected controller is coupled to a selected bridge circuit of the plurality of bridge circuits. In response to detecting the reset condition, the selected firewall circuit implements a firewall operating mode. While operating in the firewall operating mode, the selected firewall circuit is configured to control operation of the selected bridge circuit thereby isolating the selected controller from the DMA system. Firewall operating mode of firewall circuits also may be initiated by a management processor in a proactive manner.