Files
retroDE_ps2/rtl/gif_gs
thejayman77 6720caee12 Ch442: A+B scanout diagnostic (split LPDDR_STATUS[5] + first-failure snapshot)
Read-only diagnostic to disambiguate the three causes folded into
LPDDR_STATUS[5]. bit5 (0x02C) semantics are UNCHANGED.

- gs_lpddr_scanout_lb: register a live (rd_errs!=0) flag in the emif
  domain (the raw counter never crosses), and capture the FIRST raw
  underflow of each video-source-enabled session as a bundled-data
  snapshot (scan_y/nf_v/nf_s0 + base-vs-lookahead cause + line_valid +
  vphase), held stable until !enable. The existing sticky underflow_v
  latch, fetch FSM, pixel path and arbitration are untouched.
- ps2_hps_bridge: independently 2-FF sync the two split live flags;
  latch the snapshot on the rising synced-valid edge (coherent bundled
  data). New read-only regs 0x120 SCAN_DIAG_STATUS / 0x124
  SCAN_DIAG_FIRST (window addr[37:5]==9); 0x118/0x11C reserved slots
  untouched.
- top: drive 5 diag nets per scanout arm like scan_err_w; bit5 assign
  unchanged.
- tb_gs_scanout_diag (new): provokes AXI RRESP error, cold-start row-0
  starvation, first-failure capture + coherent bridge readback, and
  clear-via-video-source-disable (17/17 checks).
- Tie off the new bridge inputs in the four .*-instantiating TBs.

Sim set all PASS: focused TB, tb_ps2_hps_bridge, scanout_lb
{binomial,hstretch,psm32_256}, and the complete f52 replay (FB
byte-identical: Z 0/307200, COLOR 0/245760; sum32=0xaad0b94d).

No fix / gray-code / persistence-filter / scanout checksum. No Quartus,
no board, no push.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2026-07-21 22:40:07 -04:00
..

rtl/gif_gs

GIF path and Graphics Synthesizer logic. Matches docs/contracts/gif_gs.md.

Current contents

  • gs_stub.sv — GS shell with two architecturally distinct write ports (Ch75 namespace split):

    • reg_wr_* — privileged-block writes (16-bit offset within 0x12000000). Latches BGCOLOR (offset 0x00E0) into bg_{r,g,b}; other offsets emit EV_MODE.
    • gif_reg_* — GIF A+D register-number writes (8-bit reg# + 64-bit data). Decodes PRIM=0x00, RGBAQ=0x01, XYZF2=0x04, XYZ2=0x05, FRAME_1=0x4C, ZBUF_1=0x4E into per-register 64-bit latches; unknown reg numbers emit EV_MODE.
    • No VRAM, no drawing yet — that is the next architectural step.
  • gif_path_stub.sv — Wave 2 minimal GIF packet logger; project-local single-qword register-write format. Used by tb_bgcolor_via_dma.

  • gif_packed_stub.sv — real PS2 GIFtag parser (Ch72-Ch75). Handles PACKED (FLG=0), REGLIST (FLG=1), IMAGE (FLG=2), DISABLE (FLG=3). The REAL_AD_REG_MAP parameter selects the A+D dispatch port:

    • REAL_AD_REG_MAP=0 (default, back-compat) — drives gs_stub.reg_wr_* using a project-local 16-bit offset carried in in_data[79:64].
    • REAL_AD_REG_MAP=1 — drives gs_stub.gif_reg_* using the real PS2 8-bit reg# carried in in_data[71:64]. Source-of-truth: PCSX2 GSRegs.h.

BGCOLOR reset value

At reset, bg_{r,g,b} default to 0x40 each (mid-grey) rather than black. Rationale: this makes "gs_stub reset but no BGCOLOR write yet" visually distinct from "video output disabled / black frame" in Milestone A. Override is a BGCOLOR write from the test harness.

Pitfall: namespace conflation

Ch74 conflated GIF A+D reg numbers with GS privileged-block offsets and mapped e.g. 0x14→PMODE@0x0000. That is fiction — those are separate namespaces. Ch75 split them. ZBUF_1 is 0x4E, not 0x4F (that's ZBUF_2). When adding a new GIF-context register, source the reg# from PCSX2 GSRegs.h, never from the privileged-block map.