SAS Expander Local Error Recovery Control Circuits
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Solution Overview
Problem
Error recovery processing in SAS expanders with speed-matching buffering features overburdens the firmware, negatively impacting system performance due to the need to track and recover errors from multiple ports, reducing the effectiveness of performance enhancements.
Innovation Solution
A SAS expander with control circuits that store and forward buffered information and process errors locally, without involving the programmable processor, using a SATA host circuit to communicate with SATA end devices and a SATA target circuit to report and clear error conditions, allowing for efficient error management and reduced processing load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If error recovery processing is performed by firmware in SAS expanders with speed-matching buffering features, then error detection and recovery capability is improved, but firmware processing burden increases and system performance deteriorates
Solution Approach 1:
The patent divides the expander into two distinct processing paths: a control circuit path for error detection and recovery, and a firmware path for speed-matching buffering operations. This segmentation allows error handling to occur independently without burdening the firmware, thus maintaining system performance while improving reliability through dedicated error processing capability.
2Reliability
If firmware tracks and recovers errors from multiple ports, then comprehensive error management is improved, but processing load on firmware increases
Solution Approach 1:
The patent extracts the error tracking and recovery function from the firmware and implements it in dedicated control circuits within the expander. This extraction allows comprehensive multi-port error management to be performed by hardware logic rather than firmware, reducing firmware processing load while maintaining comprehensive error management capability across all ports.
3Adaptability or versatility
If speed-matching buffering is implemented in SAS expanders, then communication flexibility between different speed devices is improved, but overall device complexity increases
Solution Approach 1:
The patent merges the speed-matching buffering function with the existing expander structure by integrating buffer memory and control logic into the expander's fabric. This merging allows the expander to handle communications between devices of different speeds (SATA and SAS) without requiring separate dedicated buffering systems, thus improving communication flexibility while minimizing increases in overall device complexity.
Data Source
AI summary
Methods and structure for enhanced SAS expander functionality to store and forward buffered information transmitted from an initiator device to a target device and to process errors in control circuits of the expander without intervention from the general purpose programmable processor of the expander. A PHY of an expander is associated with control circuits that comprise buffering of commands to be forwarded to an end device directly coupled to the PHY. The control circuits locally process errors detected from the end device. The control circuits comprise a SATA host circuit adapted to communicate with a SATA end device to detect and clear error conditions and a SATA target circuit to communicate with one or more STP initiator devices to report and clear error conditions reported by the end device. The structures and methods may also service SAS connections (in addition to STP connections).