USB Host Controller Bandwidth Reallocation Across Bus Instances
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Solution Overview
Problem
In USB systems, individual bus instances (BIs) lack knowledge of the bandwidth usage by other BIs, leading to inefficient bandwidth allocation and potential failure in adding endpoints, resulting in degraded performance due to equal sharing of total available bandwidth.
Innovation Solution
A method and apparatus for USB host controller that includes a scheduler and resource calculator to manage BI resource allocation by maintaining bandwidth tables, determining endpoint additions, and reallocating unused bandwidth from other BIs to meet predetermined limits, ensuring no side effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If each BI is managed independently with equal bandwidth sharing, then bandwidth allocation is simple and stable, but endpoint addition fails and overall performance degrades
Solution Approach 1:
The patent introduces a bandwidth manager as an intermediary component that mediates between multiple BIs and the USB system resources. This manager maintains a bandwidth table tracking usage by each BI and performs centralized allocation decisions, enabling endpoint addition while preventing any single BI from monopolizing resources. The intermediary resolves the contradiction by providing coordinated management rather than independent management.
Solution Approach 2:
The patent implements feedback mechanisms where the bandwidth manager continuously monitors bandwidth usage by each BI through the bandwidth table and adjusts allocations accordingly. When a BI requests additional bandwidth for endpoint addition, the manager checks current usage, determines availability, and either grants or denies the request based on system-wide conditions. This feedback loop enables dynamic adaptation while maintaining overall system stability.
2Adaptability or versatility
If total bandwidth is equally divided among multiple BIs, then bandwidth allocation is fair and stable, but adding endpoints becomes unsuccessful
Solution Approach 1:
The patent transforms the static equal-bandwidth-allocation model into a dynamic system where bandwidth assignments can change based on real-time conditions. The bandwidth manager allows BIs to request additional bandwidth when needed for endpoint addition, and the system responds by reallocating from the pool of unused bandwidth. This dynamic adjustment maintains reliability through controlled management while enabling adaptability for endpoint flexibility.
Solution Approach 2:
The patent changes the bandwidth allocation parameter from fixed equal shares to variable allocations based on actual usage patterns and system conditions. The bandwidth table tracks and updates bandwidth assignments for each BI, allowing the system to grant additional bandwidth to specific BIs when endpoints need to be added, while maintaining overall stability through the manager's coordinated control.
3Productivity
If BIs are limited to equal shares of total bandwidth, then resource distribution is balanced, but overall system performance is degraded
Solution Approach 1:
The patent merges the bandwidth management functions of multiple independent BIs into a single centralized bandwidth manager. This manager consolidates the bandwidth table and allocation decisions, allowing it to view and optimize system-wide resource distribution. By combining management functions rather than maintaining separate independent controls, the system achieves improved overall performance while the merged structure actually reduces operational complexity compared to coordinating multiple independent managers.
Data Source
AI summary
A method for performing bus instance (BI) resource management in a USB host controller and associated apparatus are provided. The method applicable to the USB host controller includes: establishing a BI bandwidth table for recoding respective bandwidth usage information of multiple BIs of the USB host controller; utilizing a scheduler within the USB host controller to determine whether a predetermined command is received; utilizing the scheduler to determine whether the predetermined command indicates that any endpoint is added; utilizing a resource calculator within the USB host controller to perform a lookup operation on the BI bandwidth table, for determining whether a target bandwidth of a target BI among the multiple BIs exceeds a predetermined bandwidth limit per BI; and utilizing the resource calculator to perform at least one searching operation for collecting at least one remaining bandwidth of at least one other BI for being used by the target BI.