riscv-non-isa/tg-nexus-trace

Feedback on RISC-V Trace Connectors Specification

Closed this issue · 2 comments

ved-rivos commented
  1. "MIPI Debug & Trace Connector Recommendations" white paper (dated 7/2/2021) defines two pin options - "Narrow JTAG + Trace" and "JTAG + Trace" - for the 20-pin connector. This pin mapping supports the use of pin 14/16/18/20 as TRC_DATA[0/1/2/3] and pin 12 as TRC_CLK. It is unclear why Chapter 2 indicates that these are new additions to MIPI.
  2. Chapter 2, Table 1 - shows two pins as SerialTrace. What is the function of having two SerialTrace pins and why do they have identical names?
  3. Chapter 2, Table 1 - The layout in Table 1 does not match the mappings in Table 4 of the MIPI white paper. Specifically the JTAG mapping shown as mapping B in Table 1 is deprecated by MIPI. The Table 1 should be reconciled with MIPI and specifically identify why chapter 2 should diverge from MIPI recommendation.
  4. The option of providing power through pin 11/13 is noted by MIPI whitepaper in Table 4 as supported by ARM but not supported by MIPI. The rationale for RISC-V to support this is not clear.
  5. Please provide more rationale for chapter 3 not simply pointing to Table 11 of MIPI white paper i.e. the need for Chapter 3.
  6. Please provide the rationale for chapter 4 not being a reference to chapter 7 of the MIPI white paper.

Please provide further arguements for why this document should not be a white paper (mostly reference ARM and MIPI specifications where appropriate) instead of a normative RISC-V specification.

RobertChyla commented

@ved-rivos

Two commits:

7eea6ee
98fb6b2 (forgotten to save ...)

are IMO addressing all issues mentioned above (Google DOC comments provide more explanations).

Corresponding PDF (1.0.0_rc10, 2023-12-08) is here:

https://github.com/riscv-non-isa/tg-nexus-trace/actions/runs/7146467079

I assume after you verify it is OK, you will close this issue.

mipsrobert commented

I am closing all Connectors PDF related issues with same comments as all issues were handled via comments/discussions in SINGLE Google Docs. Relevant links are as follows:

Notes to Connectors PDF: https://docs.google.com/document/d/1iNbB7-nTiQQ4vQBzLqxtBDQxT51QeUQMd9MFOe0jsBs

Connectors PDF rc20: 221f6b1
Connectors for ARC review: 1de77dc