// retroDE_ps2 — tb_gs_raster_pipeline (Ch88) // // White-box TB pinning down the Ch88 pixel-pipeline contract: // // * Throughput: 1 candidate pixel/cycle once the pipeline is // primed. For a fully-inside primitive this means 1 emit/cycle // for N consecutive cycles, where N is the bbox pixel count. // // * Latency: from the v2-close cycle (push) to first observed // raster_pixel_emit, exactly 5 posedges: // v_close v2 commits, push_ok=1 (FIFO 0→1) // v_close+1 R_IDLE+nonempty → pop_ok=1, state ← R_SCAN // v_close+2 state=R_SCAN, S0 produces pix(0,0); s1 ← (0,0) // v_close+3 s2 ← (0,0) // v_close+4 emit register fires (raster_pixel_emit ← 1) // v_close+5 raster_pixel_emit visible to observer // i.e., 3 stages of pipeline + 1 cycle for the FIFO turn- // around + 1 cycle for the registered emit output. // // * After last S0 coord, the pipeline drains for 2 more cycles // so all in-flight pixels still emit (no truncation). // // Flow: drive PRIM/FRAME_1/RGBAQ then a single 4×4 SPRITE // (16 pixels). Capture the cycle index of every raster_pixel_emit // pulse and assert: // - exactly 16 pulses // - every adjacent pair is on consecutive cycles (delta == 1) // - first pulse lands EXACTLY 3 cycles after the pop_ok cycle // - raster_overflow stays low `timescale 1ns/1ps module tb_gs_raster_pipeline; logic clk; logic rst_n; initial clk = 1'b0; always #5 clk = ~clk; // gs_stub inputs logic gif_reg_wr_en; logic [7:0] gif_reg_num; logic [63:0] gif_reg_data; // gs_stub outputs (most are tied off — we only watch raster_*) logic [7:0] bg_r, bg_g, bg_b; logic [63:0] prim_q, rgbaq_q, xyz2_q, xyzf2_q, frame_1_q, zbuf_1_q; logic prim_complete; logic [31:0] prim_complete_count; logic [63:0] prim_v0_q, prim_v1_q, prim_v2_q; logic [63:0] prim_color_q; logic [63:0] prim_color_v0_q, prim_color_v1_q, prim_color_v2_q; trace_pkg::vertex_t prim_v0_decoded_q, prim_v1_decoded_q, prim_v2_decoded_q; trace_pkg::color_t prim_v0_color_decoded_q, prim_v1_color_decoded_q, prim_v2_color_decoded_q; logic pixel_emit; logic [31:0] pixel_emit_count; logic [11:0] pixel_x_q, pixel_y_q; logic [63:0] pixel_color_q; logic [8:0] pixel_fbp_q; logic [5:0] pixel_fbw_q, pixel_psm_q; logic [31:0] pixel_fb_addr_q; logic raster_pixel_emit; logic [31:0] raster_pixel_emit_count; logic [11:0] raster_pixel_x_q, raster_pixel_y_q; logic [63:0] raster_pixel_color_q; logic [31:0] raster_pixel_fb_addr_q; logic raster_active; logic raster_overflow; logic raster_degenerate; logic ev_valid; trace_pkg::subsys_e ev_subsys; trace_pkg::event_e ev_event; logic [63:0] ev_arg0, ev_arg1, ev_arg2, ev_arg3; logic [31:0] ev_flags; gs_stub u_gs ( .clk(clk), .rst_n(rst_n), .reg_wr_en(1'b0), .reg_wr_addr(16'd0), .reg_wr_data(64'd0), .gif_reg_wr_en(gif_reg_wr_en), .gif_reg_num(gif_reg_num), .gif_reg_data(gif_reg_data), .bg_r(bg_r), .bg_g(bg_g), .bg_b(bg_b), .prim_q(prim_q), .rgbaq_q(rgbaq_q), .xyz2_q(xyz2_q), .xyzf2_q(xyzf2_q), .frame_1_q(frame_1_q), .zbuf_1_q(zbuf_1_q), .prim_complete(prim_complete), .prim_complete_count(prim_complete_count), .prim_v0_q(prim_v0_q), .prim_v1_q(prim_v1_q), .prim_v2_q(prim_v2_q), .prim_color_q(prim_color_q), .prim_color_v0_q(prim_color_v0_q), .prim_color_v1_q(prim_color_v1_q), .prim_color_v2_q(prim_color_v2_q), .prim_v0_decoded_q(prim_v0_decoded_q), .prim_v1_decoded_q(prim_v1_decoded_q), .prim_v2_decoded_q(prim_v2_decoded_q), .prim_v0_color_decoded_q(prim_v0_color_decoded_q), .prim_v1_color_decoded_q(prim_v1_color_decoded_q), .prim_v2_color_decoded_q(prim_v2_color_decoded_q), .pixel_emit(pixel_emit), .pixel_emit_count(pixel_emit_count), .pixel_x_q(pixel_x_q), .pixel_y_q(pixel_y_q), .pixel_color_q(pixel_color_q), .pixel_fbp_q(pixel_fbp_q), .pixel_fbw_q(pixel_fbw_q), .pixel_psm_q(pixel_psm_q), .pixel_fb_addr_q(pixel_fb_addr_q), .raster_pixel_emit(raster_pixel_emit), .raster_pixel_emit_count(raster_pixel_emit_count), .raster_pixel_x_q(raster_pixel_x_q), .raster_pixel_y_q(raster_pixel_y_q), .raster_pixel_color_q(raster_pixel_color_q), .raster_pixel_fb_addr_q(raster_pixel_fb_addr_q), .raster_active(raster_active), .raster_overflow(raster_overflow), .raster_degenerate(raster_degenerate), .ev_valid(ev_valid), .ev_subsys(ev_subsys), .ev_event(ev_event), .ev_arg0(ev_arg0), .ev_arg1(ev_arg1), .ev_arg2(ev_arg2), .ev_arg3(ev_arg3), .ev_flags(ev_flags) ); // Per-cycle index. Increments every posedge clk after rst_n. int cycle_idx; initial cycle_idx = 0; always_ff @(posedge clk) if (rst_n) cycle_idx <= cycle_idx + 1; // Capture the cycle of the v2 close (last drive_reg call) and // the cycle every raster_pixel_emit pulse fires. int v_close_cycle; int emit_cycles [0:31]; int emit_count; int errors; initial begin v_close_cycle = -1; emit_count = 0; errors = 0; end always_ff @(posedge clk) begin if (rst_n && raster_pixel_emit && emit_count < 32) begin emit_cycles[emit_count] <= cycle_idx; emit_count <= emit_count + 1; end end task automatic step_drive(input logic wr_en, input logic [7:0] num, input logic [63:0] data); @(negedge clk); gif_reg_wr_en = wr_en; gif_reg_num = num; gif_reg_data = data; @(posedge clk); endtask task automatic drive_reg(input logic [7:0] num, input logic [63:0] data); step_drive(1'b1, num, data); endtask task automatic drive_idle(); step_drive(1'b0, 8'd0, 64'd0); endtask function automatic logic [63:0] xyz2_data(input logic [11:0] x_int, input logic [11:0] y_int); return {32'd0, y_int, 4'd0, x_int, 4'd0}; endfunction localparam logic [7:0] R_PRIM = 8'h00; localparam logic [7:0] R_RGBAQ = 8'h01; localparam logic [7:0] R_XYZ2 = 8'h05; localparam logic [7:0] R_FRAME_1 = 8'h4C; localparam logic [63:0] PRIM_SPRITE = 64'd6; localparam logic [63:0] FRAME_1_VAL = 64'h0000_0000_000A_0002; localparam logic [63:0] RGBAQ_VAL = 64'h0000_0000_FF00_30FF; initial begin rst_n = 1'b0; gif_reg_wr_en = 1'b0; gif_reg_num = 8'd0; gif_reg_data = 64'd0; repeat (4) @(posedge clk); rst_n = 1'b1; repeat (2) @(posedge clk); drive_reg(R_PRIM, PRIM_SPRITE); drive_reg(R_FRAME_1, FRAME_1_VAL); drive_reg(R_RGBAQ, RGBAQ_VAL); // 4×4 sprite — bbox=[0..3]×[0..3] = 16 pixels. drive_reg(R_XYZ2, xyz2_data(12'd0, 12'd0)); // v1 drive_reg(R_XYZ2, xyz2_data(12'd3, 12'd3)); // v2 — close S1 v_close_cycle = cycle_idx; // capture posedge index of v2 close // Stop driving (deassert gif_reg_wr_en) and let the // pipeline run. Without this idle, gif_reg_wr_en stays // high and re-commits the v2 vertex every cycle, kicking // off extra sprites and overflowing the FIFO. drive_idle(); repeat (40) @(posedge clk); // ---- Assertions ---- $display("[tb_gs_raster_pipeline] v_close_cycle=%0d emit_count=%0d raster_pixel_emit_count=%0d raster_overflow=%b", v_close_cycle, emit_count, raster_pixel_emit_count, raster_overflow); for (int i = 0; i < emit_count; i++) begin $display("[tb_gs_raster_pipeline] emit[%0d] @ cyc=%0d", i, emit_cycles[i]); end if (emit_count != 16) begin $error("emit_count=%0d (expected 16 for 4×4 sprite)", emit_count); errors = errors + 1; end if (raster_pixel_emit_count != 32'd16) begin $error("raster_pixel_emit_count=%0d (expected 16)", raster_pixel_emit_count); errors = errors + 1; end if (raster_overflow !== 1'b0) begin $error("raster_overflow=%b (expected 0)", raster_overflow); errors = errors + 1; end // Throughput: every consecutive pair of emits must be on // adjacent cycles (delta == 1). 1 pixel/cycle. for (int i = 1; i < emit_count; i++) begin int d; d = emit_cycles[i] - emit_cycles[i-1]; if (d != 1) begin $error("throughput break: emit[%0d]@%0d vs emit[%0d]@%0d (delta=%0d, expected 1)", i-1, emit_cycles[i-1], i, emit_cycles[i], d); errors = errors + 1; end end // Latency: 5 posedges from v_close to first observed // raster_pixel_emit (see header for breakdown). if (emit_count > 0) begin int expected_first; int actual_first; expected_first = v_close_cycle + 5; actual_first = emit_cycles[0]; if (actual_first != expected_first) begin $error("first-emit latency: emit[0]@cyc=%0d (expected %0d = v_close+5)", actual_first, expected_first); errors = errors + 1; end end if (errors == 0) $display("[tb_gs_raster_pipeline] PASS"); else $display("[tb_gs_raster_pipeline] FAIL"); $finish; end initial begin #5000000; $error("[tb_gs_raster_pipeline] timeout"); $finish; end endmodule : tb_gs_raster_pipeline