Files
retroDE_ps2/rtl/gif_gs
thejayman77 6319d7ca85 Ch443d: registered AXI R buffer (texcache fill) + drop fill_data_q reset
Closes the last currently-visible EMIF-handshake -> FSM setup family the
Ch443c fit exposed (-0.043/-0.022/-0.005 ns), the read-response analogue
of the AW/W buffers.

- gs_axi_r_regbuf: one-entry FULLY-registered AXI R buffer (the R twin of
  gs_axi_w_regbuf). Buffers the complete {rdata,rresp,rlast}; u_rready =
  !full only (NO combinational dependence on the texture FSM's d_rready);
  captures on u_rvalid && u_rready; d_rvalid = full with the payload held
  stable until d_rvalid && d_rready; resets only . Inserted between
  read-arbiter s2 and gs_texture_cache (u_texf_rbuf). The arbiter is
  unchanged -- it completes its R transaction into the buffer, which then
  owns delivery to the fill FSM. Cuts EMIF rvalid/rdata -> fst.F_R.
- gs_texture_cache: drop the unobservable fill_data_q reset. F_DRAIN (its
  only reader) is reachable only after F_R loads it, so the reset value is
  never observed; removing it kills the separate lock_sync|dreg[1] ->
  fill_data_q[80] setup path (-0.005 ns).
- New tb_gs_axi_r_regbuf: exactly-once/in-order, randomized responses +
  stalls, full backpressure, the full && d_rready no-fall-through case,
  {rdata,rresp,rlast} stability, reset-while-empty AND reset-while-full.

All green: r-buffer TB, texture_cache, texture_psmt8_clut, scanout_lb,
scanout_restart, scanout_diag, ps2_hps_bridge, rd_arb, and the complete
f52 replay BYTE-IDENTICAL (Z 0/307200, COLOR 0/245760). No Quartus/board/
push from here.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2026-07-23 10:03:01 -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.