rtl/gfx: implement SP fetch

1 files changed, 63 insertions, 0 deletions

diff --git a/rtl/gfx/gfx_sp_widener.sv b/rtl/gfx/gfx_sp_widener.sv
new file mode 100644
index 0000000..92101ca
--- /dev/null
+++ b/rtl/gfx/gfx_sp_widener.sv
@@ -0,0 +1,63 @@
+`include "gfx/gfx_defs.sv"
+
+module gfx_sp_widener
+#(parameter WIDTH=0) // Quartus no soporta 'parameter type'
+(
+	input  logic                   clk,
+	                               rst_n,
+
+	input  logic                   word_waitrequest,
+	                               word_readdatavalid,
+	input  vram_word               word_readdata,
+	output vram_addr               word_address,
+	output logic                   word_read,
+
+	input  logic                   wide_read,
+	input  logic[WIDTH - 1:0]      wide_address,
+	output logic                   wide_waitrequest,
+	                               wide_readdatavalid,
+
+	output logic[DATA_WIDTH - 1:0] wide_readdata
+);
+
+	// Este módulo existe para fingir que la DE1-SoC tiene un bus de SDRAM más ancho
+
+	localparam WIDE_BITS = $bits(vram_addr) - WIDTH,
+	           WIDE_SIZE = 1 << WIDE_BITS,
+	           DATA_WIDTH = $bits(vram_word) << WIDE_BITS;
+
+	vram_word shift_in[WIDE_SIZE];
+	logic[WIDE_BITS - 1:0] address_count, read_count;
+
+	assign word_read = wide_read;
+	assign word_address = {wide_address, address_count};
+	assign wide_waitrequest = word_waitrequest || !(&address_count);
+
+	always_comb
+		for (integer i = 0; i < WIDE_SIZE; ++i)
+			wide_readdata[$bits(vram_word) * i +: $bits(vram_word)] = shift_in[i];
+
+	always_ff @(posedge clk or negedge rst_n)
+		if (!rst_n) begin
+			read_count <= 0;
+			address_count <= 0;
+			wide_readdatavalid <= 0;
+		end else begin
+			if (word_read && !word_waitrequest)
+				address_count <= address_count + 1;
+
+			if (word_readdatavalid)
+				read_count <= read_count + 1;
+
+			wide_readdatavalid <= word_readdatavalid && &read_count;
+		end
+
+	always_ff @(posedge clk)
+		if (word_readdatavalid) begin
+			for (integer i = 0; i < WIDE_SIZE - 1; ++i)
+				shift_in[i] <= shift_in[i + 1];
+
+			shift_in[WIDE_SIZE - 1] <= word_readdata;
+		end
+
+endmodule