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>
Per Codex review of dd7ca4f (testbench only, RTL unchanged):
1. Stall check now requires d_wvalid to REMAIN asserted (catches a deassert) and
compares the COMPLETE {d_wdata,d_wstrb,d_wlast} against the held beat, not just
d_wdata.
2. Added saw_full_and_ready coverage flag (set on dut.full && d_wready) and a final
check that FAILS if the distinguishing no-bypass case was never observed.
No RTL change, no simulations, no Quartus.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Cuts the lone remaining EMIF setup fail (-0.016 ns, -0.259 skew): the combinational
EMIF gen_p2c_ff -> wr_arb s2_wready -> gs_lpddr_z_rmw next-state (st, endpoint
labelled S_FILL_R via the shared encoded state register).
New gs_axi_w_regbuf: fully-registered one-entry W buffer (Option B per Codex).
- u_wready = !full ONLY (registered occupancy) -> EMIF WREADY never reaches the Z
FSM combinationally. NOT a fall-through skid (no !full-OR-d_wready term).
- Buffers WDATA/WSTRB/WLAST; downstream held stable until accepted; exactly-once.
- AW/B untouched; arbiter bready_q unchanged (still arms on real EMIF W handshake).
- z_rmw may enter B-wait once the beat is buffered -- safe: EMIF cannot return B
until the buffered beat reaches it. Single-beat writes -> the 1-beat/2-cycle
buffer rate is far above the Z write rate (no new FIFO pressure).
Wired in zc_emit between u_z W output (zi_*) and the z_w* ports. New file in sim
Makefile RTL_SRCS + synth QSF (both). Focused tb_gs_axi_w_regbuf: exactly-once/order/
payload scoreboard + no-combinational-bypass check (u_wready===!full incl. full &&
d_wready) + downstream-stable check; standalone target + in make run. Texture-cache
+0.016 paths NOT touched. No simulations or Quartus run.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Per Codex review of 471c1af:
1. tb_gs_async_fifo QUAD_WIDTH4 variant now runs at the PRODUCTION 93-bit width
(exercising the odd 23/23/23/24 remainder split) and drives a DISTINCT NONZERO
pattern into every width bank (seq XOR per-bank constants, bank2 inverted), with
the scoreboard checking the FULL reconstructed word. A swapped/broken/zeroed
upper bank now changes the word and trips the scoreboard. Depth-half crossing
(DEPTH=8) + wrap/full coverage retained. mk() is generate-guarded so the 32-bit
variants never elaborate the 93-bit selects.
2. Softened gs_async_fifo comments: 'same total M20K' -> EXPECTED-similar, pending
synthesis (fact -> expectation).
No simulations or Quartus run. Awaiting review before any sim.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Candidate 2 from the accepted structural proposal. Adds a QUAD_WIDTH4_READ
generate branch to gs_async_fifo: like QUADRANT_READ (2 depth x 2 width) but
splits the payload into FOUR width banks, so each preserved read-address launch
register drives ~half the M20K load (targets the 310MHz raddr_hi1_q->mem_hi1
setup family, WNS -0.103). Keeps QUADRANT_READ's proven 2:1 depth OUTPUT selector
unchanged (no new/deeper mux, per the doc's warning). Depth (8192), one-cycle
read latency, ordering, CDC, capacity, and interface are identical.
zc_emit u_req switched QUADRANT_READ->QUAD_WIDTH4_READ. New default-off param
leaves the other two gs_async_fifo instances byte-identical. TB gains a
TEST_QUAD_WIDTH4 variant + standalone Makefile target tb_gs_async_fifo_quad_width4.
NO simulations or Quartus run (per authorization). Awaiting review before any sim.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
The fog blend's tex_color*F multiply landed on the texture->color critical path
(u_texcache RAM -> u_tex|tex_color -> mult_126 -> raster_pixel_color_q, 46ns,
-6.165ns setup). Fog is a proven no-op for the current board scene (96.5% F=255),
so pay zero for it here.
FOG_ENABLE (default 1, byte-identical fog) added to gs_stub; each fog mux gated
(FOG_ENABLE && ras_fge) so FOG_ENABLE=0 constant-folds the entire fog cone away
(multiply, FOGCOL adders, s2_fog_f/persp_fog_f5 interp). Threaded through
top_psmct32_raster_demo_bram; set FOG_ENABLE(1'b0) on the active GS_SH3_LPDDR_FB
board arm (elsif at :1086, the one the QSF profile compiles). Fog stays default-on
everywhere else.
Verified: FOG_ENABLE=1 fog TBs unchanged PASS; FOG_ENABLE=0 (new tb_gs_fog_disabled
+ board scene TB) emits raw color = pre-fog datapath; board elaborates clean.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Per-vertex GS fog end-to-end (gs_stub emit incl. persp_emit5, gs_prim_list_feeder
XYZ2->XYZF2 on PRIM.FGE, gs_make_sh3_scheduler_fixture.py F/FGE packing), new fog
TBs, fidelity attribution tooling. Functional baseline before removing the dead
bilinear lerp8 clamps (Codex: 161-node comb loop -> -0.042ns setup fail).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
RTL (GS rasterizer, EE core stub, platform bridge, LPDDR4B path), sim regression
(272 TBs), docs, and tooling. Copyrighted PS2 content (BIOS, game code, GS dumps,
and all dump-derived textures/traces) is excluded via .gitignore and stays local.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
thejayman77