Intermediate Device Link Training via Remote State Feedback
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Solution Overview
Problem
The DisplayPort protocol lacks management of both local and remote links when an intermediate device using a different protocol is connected between a DisplayPort source and sink device, leading to inefficiencies and potential system failures due to mismatched lane numbers and transmission rates.
Innovation Solution
An intermediate device with a state machine generates and stores state information about the remote link, allowing the source device to perform end-to-end link training by accessing this information and configuring the local link to match the remote link's parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the DisplayPort protocol performs traditional link training without intermediate device management, then the link training process is simple, but lane number and transmission rate mismatches occur when intermediate devices are connected
Solution Approach 1:
The patent introduces an intermediate device (such as a Thunderbolt switch or extender) that acts as a mediator between the DisplayPort source and sink devices. This intermediate device includes a state machine that tracks the operational status of remote links and stores this state information in registers, enabling coordinated link training across multiple segments while preventing lane and rate mismatches.
Solution Approach 2:
The state machine in the intermediate device continuously monitors the operational status of remote links and feeds back this information through dedicated registers. This feedback mechanism allows the DisplayPort protocol to adapt its link training process based on real-time conditions, ensuring reliable configuration even in complex multi-segment topologies.
2Productivity
If the source device configures the local link independently without knowing remote link status, then the configuration process is fast, but lane and bit rate symmetry cannot be ensured
Solution Approach 1:
The state machine in the intermediate device performs preliminary actions by pre-establishing and tracking the operational status of remote links before the DisplayPort source device initiates link training. This advance preparation ensures that when the source device configures the local link, the remote link status is already known, enabling symmetric configuration without requiring iterative adjustments that would slow down the process.
3Adaptability or versatility
If an intermediate device converts traffic between different protocols, then protocol compatibility is achieved, but link management complexity increases
Solution Approach 1:
The intermediate device serves as a protocol translation mediator, converting traffic between DisplayPort and other protocols (such as Thunderbolt). By embedding a state machine that independently tracks remote link status, the patent separates the protocol conversion function from the link management function, allowing each to be optimized independently while reducing overall system complexity.
Data Source
AI summary
Information is provided to a source device during link training regarding the state of a remote link when an intermediate device using a different protocol is connected between source and sink devices. The intermediate device includes two controllers connected by a cable, the first controller being connected to the source device and the second controller being connected to the sink device. State information regarding the remote device may be provided by a state machine that stores data to a register on the intermediate device. Based on the state of the remote link, the source device is able to generate a representation of the end to end link between the source and sink device, and to perform link training accordingly.