From ec2f4c0e20aaa130359630299362d03ce41d585c Mon Sep 17 00:00:00 2001
From: Alejandro Soto <alejandro@34project.org>
Date: Mon, 20 Nov 2023 16:23:17 -0600
Subject: rtl/gfx: implement program header command registers

---
 rtl/gfx/gfx_cmd.sv  | 60 +++++++++++++++++++++++++++++++++++++++--------------
 rtl/gfx/gfx_defs.sv |  5 +++++
 2 files changed, 50 insertions(+), 15 deletions(-)

(limited to 'rtl/gfx')

diff --git a/rtl/gfx/gfx_cmd.sv b/rtl/gfx/gfx_cmd.sv
index 28fd4b1..40e2ccb 100644
--- a/rtl/gfx/gfx_cmd.sv
+++ b/rtl/gfx/gfx_cmd.sv
@@ -16,9 +16,16 @@ module gfx_cmd
 	output logic       swap_buffers,
 	                   enable_clear,
 	                   start_clear,
-	output rgb24       clear_color
+	output rgb24       clear_color,
+
+	output logic       program_start,
+	output cmd_word    program_header_base,
+	                   program_header_size
 );
 
+	rgb24 next_clear_color;
+	logic do_start_clear, next_start_clear, next_enable_clear, next_swap_buffers;
+
 	struct packed
 	{
 		logic[4:0] mbz;
@@ -28,17 +35,15 @@ module gfx_cmd
 		rgb24      clear_color;
 	} readdata_scan, writedata_scan;
 
-	assign readdata_scan.clear_color = clear_color;
+	assign cmd_readdata = readdata_scan;
+
+	assign writedata_scan = cmd_writedata;
 	assign readdata_scan.mbz = 0;
+	assign readdata_scan.clear_color = clear_color;
 	assign readdata_scan.enable_clear = enable_clear;
 	assign readdata_scan.swap_buffers = swap_buffers;
 
-	assign writedata_scan = cmd_writedata;
-
-	assign cmd_readdata = readdata_scan;
-
-	rgb24 next_clear_color;
-	logic next_start_clear, next_enable_clear, next_swap_buffers;
+	assign do_start_clear = writedata_scan.start_frame && writedata_scan.enable_clear;
 
 	always_ff @(posedge clk or negedge rst_n)
 		if (!rst_n) begin
@@ -49,21 +54,35 @@ module gfx_cmd
 			next_start_clear <= 0;
 			next_enable_clear <= 0;
 			next_swap_buffers <= 0;
+
+			program_start <= 0;
 		end else begin
 			start_clear <= 0;
+			program_start <= 0;
+
 			if (vsync) begin
 				start_clear <= next_start_clear;
 				enable_clear <= next_enable_clear;
 				swap_buffers <= next_swap_buffers;
 			end
 
-			if (cmd_write) begin
-				next_enable_clear <= writedata_scan.enable_clear;
-				next_swap_buffers <= writedata_scan.swap_buffers;
+			if (cmd_write)
+				unique case (cmd_address[1:0])
+					`GFX_CMD_REG_ID: ;
 
-				if (!next_start_clear)
-					next_start_clear <= writedata_scan.start_frame && writedata_scan.enable_clear;
-			end
+					`GFX_CMD_REG_SCAN: begin
+						next_enable_clear <= writedata_scan.enable_clear;
+						next_swap_buffers <= writedata_scan.swap_buffers;
+
+						if (!next_start_clear)
+							next_start_clear <= do_start_clear;
+					end
+
+					`GFX_CMD_REG_HEADER_BASE: ;
+
+					`GFX_CMD_REG_HEADER_SIZE:
+						program_start <= 1;
+				endcase
 		end
 
 	always_ff @(posedge clk) begin
@@ -71,7 +90,18 @@ module gfx_cmd
 			clear_color <= next_clear_color;
 
 		if (cmd_write)
-			next_clear_color <= writedata_scan.clear_color;
+			unique case (cmd_address[1:0])
+				`GFX_CMD_REG_ID: ;
+
+				`GFX_CMD_REG_SCAN:
+					next_clear_color <= writedata_scan.clear_color;
+
+				`GFX_CMD_REG_HEADER_BASE:
+					program_header_base <= cmd_writedata;
+
+				`GFX_CMD_REG_HEADER_SIZE:
+					program_header_size <= cmd_writedata;
+			endcase
 	end
 
 endmodule
diff --git a/rtl/gfx/gfx_defs.sv b/rtl/gfx/gfx_defs.sv
index 20102a4..fa297e6 100644
--- a/rtl/gfx/gfx_defs.sv
+++ b/rtl/gfx/gfx_defs.sv
@@ -188,6 +188,11 @@ typedef logic[`GFX_LANE_ADDR_BITS - 1:0] vram_lane_addr;
 typedef logic[5:0]  cmd_addr;
 typedef logic[31:0] cmd_word;
 
+`define GFX_CMD_REG_ID          2'b00
+`define GFX_CMD_REG_SCAN        2'b01
+`define GFX_CMD_REG_HEADER_BASE 2'b10
+`define GFX_CMD_REG_HEADER_SIZE 2'b11
+
 typedef struct packed
 {
 	logic[$bits(cmd_word) - $bits(vram_insn_addr) - `GFX_INSN_SUBWORD_BITS - 1:0] pad;
-- 
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