Cache Debug Control Registers for Hardware Diagnostic Access
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Solution Overview
Problem
Current hardware debug systems lack defined debug commands for hardware debugging of processor caches, making it difficult to read or write cache-related information such as cached data, error protection information, and status information effectively.
Innovation Solution
Implementing debug circuitry with control registers and intermediate debug commands that allow for abstract commands to access cache data, parity bits, and status information, enabling direct hardware manipulation of cache contents through specific register operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If hardware debug circuitry is implemented without defined debug commands for caches, then the basic debug infrastructure is simple, but the ability to read or write cache-related information is insufficient
Solution Approach 1:
The debug module is extended to handle multiple cache-related operations (read, write, parity check, status inspection) through a unified interface. The existing debug infrastructure is made multi-functional by introducing cache-specific commands that operate on cache data, parity bits, and status information, allowing a single debug system to serve both general debugging and specialized cache debugging needs.
Solution Approach 2:
Cache control registers serve as intermediary structures between the debug module and cache contents. These registers act as mediators that translate debug commands into cache-specific operations, enabling indirect access to cache data, parity information, and status without requiring direct cache manipulation. The intermediary registers buffer and manage the complex cache debugging operations.
2Measurement precision
If direct access to cache data and parity bits is enabled, then debugging precision is improved, but the risk of introducing errors increases
Solution Approach 1:
Parity check bits are used as feedback mechanisms to verify cache data integrity. When cache data is read or written through the debug interface, the associated parity bits are automatically checked to detect any corruption or errors. This feedback loop provides real-time error detection, allowing the system to identify and correct issues before they propagate, thereby enabling precise cache access while maintaining data integrity.
Solution Approach 2:
Error protection information (parity bits) is pre-calculated and stored alongside cache data to cushion against potential errors. Before cache operations are performed, the parity information is prepared in advance, creating a protective layer that can absorb and detect errors without compromising the entire cache system. This beforehand cushioning allows safe exploration and manipulation of cache contents.
3Loss of information
If comprehensive cache information access is implemented, then debugging completeness is improved, but the operation complexity increases
Solution Approach 1:
Cache debugging operations are segmented into distinct functional categories: data access commands, parity check commands, and status inspection commands. Each segment handles a specific aspect of cache information, allowing the debug module to comprehensively access all cache-related information while presenting a simplified, organized interface. The segmentation breaks down the complex task of complete cache inspection into manageable, specialized operations.
Solution Approach 2:
The debug interface is extended into a new dimension by adding cache-specific control registers and commands that operate alongside the existing debug architecture. This dimensional extension allows comprehensive cache information access (data, parity, status) without complicating the fundamental debug operation flow. The new dimension provides additional capabilities while maintaining compatibility with existing debug procedures.
Data Source
AI summary
Techniques are disclosed relating to cache debug using control registers based on debug commands. In some embodiments, an apparatus includes a processor core, debug circuitry, and control circuitry. In some embodiments, the debug circuitry is configured to receive external debug inputs and send abstract commands to the processor core based on the external debug inputs. In some embodiments, the control circuitry is configured to, in response to an abstract command to read data from the cache: write cache address information to a first control register, assert a trigger signal to cause a read of the data from the cache to a second control register, based on the cache address information in the first control register, and send data from the second control register to the debug circuitry. In various embodiments, this may facilitate hardware cache debug using debug circuitry that also controls software debugging.