rtl/gfx: implement edge offset setup

2 files changed, 52 insertions, 0 deletions

diff --git a/rtl/gfx/gfx_defs.sv b/rtl/gfx/gfx_defs.sv
index 6e96b4e..17ed7c0 100644
--- a/rtl/gfx/gfx_defs.sv
+++ b/rtl/gfx/gfx_defs.sv
@@ -48,8 +48,16 @@ typedef struct packed
 	logic[9:0] r, g, b;
 } rgb30;
 
+typedef logic signed[31:0] fixed;
+
+`define FIXED_FRAC 16
+
 `define GFX_MASK_SRAM_STAGES 3
 `define GFX_MASK_STAGES      (1 + `GFX_MASK_SRAM_STAGES + 1)
 `define GFX_SCAN_STAGES      3 // Ajustable
 
+`define GFX_RASTER_BITS    2
+`define GFX_RASTER_SIZE    (1 << GFX_RASTER_BITS)
+`define GFX_RASTER_OFFSETS (1 << (2 * GFX_RASTER_BITS))
+
 `endif
diff --git a/rtl/gfx/gfx_setup_offsets.sv b/rtl/gfx/gfx_setup_offsets.sv
new file mode 100644
index 0000000..3b615d5
--- /dev/null
+++ b/rtl/gfx/gfx_setup_offsets.sv
@@ -0,0 +1,44 @@
+`include "gfx/gfx_defs.sv"
+
+module gfx_setup_offsets
+(
+	input  logic  clk,
+
+	input  fixed inc_x,
+	             inc_y,
+	input  logic stall,
+
+	output fixed offsets[`GFX_RASTER_OFFSETS]
+);
+
+	fixed x_hold[`GFX_RASTER_SIZE], y_hold[`GFX_RASTER_SIZE],
+	      x_multiples[`GFX_RASTER_SIZE], y_multiples[`GFX_RASTER_SIZE];
+
+	// Asume GFX_RASTER_BITS == 2. Los ceros deberían optimizarse trivialmente
+	assign x_multiples[0] = 0;
+	assign y_multiples[0] = 0;
+	assign x_multiples[1] = inc_x;
+	assign y_multiples[1] = inc_y;
+	assign x_multiples[2] = inc_x << 1;
+	assign y_multiples[2] = inc_y << 1;
+	assign x_multiples[3] = (inc_x << 1) + a;
+	assign y_multiples[3] = (inc_y << 1) + b;
+
+	genvar i;
+	generate
+		for (i = 0; i < `GFX_RASTER_SIZE; ++i) begin: multiples
+			always_ff @(posedge clk)
+				if (!stall) begin
+					x_hold[i] <= x_multiples[i];
+					y_hold[i] <= y_multiples[i];
+				end
+		end
+
+		for (i = 0; i < `GFX_RASTER_OFFSETS; ++i) begin: permutations
+			always_ff @(posedge clk)
+				if (!stall)
+					offsets[i] <= x_hold[i % `GFX_RASTER_SIZE] + y_hold[i / `GFX_RASTER_SIZE];
+		end
+	endgenerate
+
+endmodule