tree 6417b388a2cb4b22f7a29868906e6129a4334573
parent 21d428a75bf775d9bf81967cc4a04af3dbc29114
author Alex Van Damme <atv@google.com> 1753400695 -0700
committer Alex Van Damme <atv@google.com> 1753481155 -0700

feat(debug): Transition debug module to CSR-based interface

This commit refactors the debug module's external interface, moving from direct pin-level connections to a memory-mapped CSR (Control and Status Register) interface accessible via the AXI bus. This change provides a more structured and extensible mechanism for controlling and interacting with the debug module.

Key changes include:

- **Hardware:**
    - The `CoreAxi` top-level module is updated to connect the debug module to the new CSR interface, removing the direct `dm` port.
    - `CoreAxiCSR` is enhanced with a set of registers for debug requests and responses, including registers for address, data, operation, and status.
    - The debug module's request and response signals are now driven by these CSRs, enabling control via AXI writes and reads.

- **Testbench:**
    - The `CoreMiniAxiInterface` is significantly updated to use the new CSR-based communication protocol.
    - The `dm_req_agent` and `dm_rsp_agent`, which previously managed the pin-level protocol, have been removed.
    - The `dm_read` and `dm_write` functions are rewritten to perform the multi-step process of writing to the request CSRs, polling the status CSR, and reading the response CSRs.
    - All debug-related tests are updated to use the new `dm_read` and `dm_write` functions.

- **Documentation:**
    - The debug module documentation is updated to describe the new CSR-based command protocol.
    - A table of the new AXI CSRs is added, including their addresses and descriptions.
    - The command examples are updated to reflect the new multi-step process for reading and writing GPRs via the CSR interface.

This refactoring simplifies the hardware interface, improves the robustness of the testbench, and provides a clearer and more comprehensive programming model for external debuggers.

Change-Id: I39be61d805d0e1236550a33a40dbb20f91da0d67