From 03d9d7ea8fd3f90d27b7cf20fd2900b374303d47 Mon Sep 17 00:00:00 2001
From: Peter McGoron <code@mcgoron.com>
Date: Sat, 20 Jan 2024 15:23:40 -0500
Subject: [PATCH] add bram

---
 gateware/rtl/Makefile       |  2 ++
 gateware/rtl/bram/Makefile  | 15 +++++++++
 gateware/rtl/bram/bram.v.m4 | 66 +++++++++++++++++++++++++++++++++++++
 gateware/soc.py             |  6 ++++
 4 files changed, 89 insertions(+)
 create mode 100644 gateware/rtl/bram/Makefile
 create mode 100644 gateware/rtl/bram/bram.v.m4

diff --git a/gateware/rtl/Makefile b/gateware/rtl/Makefile
index 027ec6c..836ed91 100644
--- a/gateware/rtl/Makefile
+++ b/gateware/rtl/Makefile
@@ -15,6 +15,8 @@ make_control_loop:
 	cd control_loop && make codegen
 make_waveform:
 	cd waveform && make codegen
+make_bram:
+	cd bram && make bram
 clean:
 	cd base && make clean
 	cd spi && make clean
diff --git a/gateware/rtl/bram/Makefile b/gateware/rtl/bram/Makefile
new file mode 100644
index 0000000..1263ca3
--- /dev/null
+++ b/gateware/rtl/bram/Makefile
@@ -0,0 +1,15 @@
+# Copyright 2024 (C) Peter McGoron
+# This file is a part of Upsilon, a free and open source software project.
+# For license terms, refer to the files in `doc/copying` in the Upsilon
+# source distribution.
+
+.PHONY: codegen
+
+all: codegen
+####### Codegen ########
+
+include ../common.makefile
+CODEGEN_FILES=bram.v
+codegen: ${CODEGEN_FILES}
+clean:
+	rm -rf obj_dir *.fst ${CODEGEN_FILES}
diff --git a/gateware/rtl/bram/bram.v.m4 b/gateware/rtl/bram/bram.v.m4
new file mode 100644
index 0000000..0bb31b9
--- /dev/null
+++ b/gateware/rtl/bram/bram.v.m4
@@ -0,0 +1,66 @@
+m4_changequote(`⟨', `⟩')
+m4_changecom(⟨/*⟩, ⟨*/⟩)
+
+/* Copyright 2024 (C) Peter McGoron
+ * This file is a part of Upsilon, a free and open source software project.
+ * For license terms, refer to the files in `doc/copying` in the Upsilon
+ * source distribution.
+ *
+ * BRAM to Wishbone interface.
+ */
+module bram_interface #(
+	/* This is the last INDEX of the word array, which is indexed in
+	 * words, not octets. */
+	parameter [WORD_AMNT_WID-1:0] WORD_AMNT = 2047,
+	/* Width of the memory bus */
+	parameter BUS_WID = 32,
+	/* Width of a request. */
+	parameter WORD_WID = 32,
+	/* Bitmask used to extract the RAM location in the buffer. */
+	parameter ADDR_MASK = 32'h1FFF
+) (
+	input clk,
+
+	input wb_cyc,
+	input wb_stb,
+	input wb_we,
+	input [4-1:0] wb_sel,
+	input [BUS_WID-1:0] wb_addr,
+	input [BUS_WID-1:0] wb_data_i,
+	output reg wb_ack,
+	output wb_stall,
+	output reg [BUS_WID-1:0] wb_data_o,
+);
+
+assign wb_stall = wb_ack;
+
+reg [BUS_WID-1:0] buffer [WORD_AMNT:0];
+
+m4_define(⟨bufwrite⟩,  ⟨begin
+	buffer[mem_addr & ADDR_MASK] <=
+		(buffer[wb_addr & ADDR_MASK] & $1)
+		| wb_data_i[$2];
+end⟩)
+
+always @ (posedge clk) if (wb_cyc && wb_stb && !wb_ack)
+	if (!wb_we) begin
+		wb_data_o <= buffer[wb_addr & ADDR_MASK];
+		wb_ack <= 1;
+	end else begin
+		wb_ack <= 1;
+		case (wb_sel)
+		4'b1111: buffer[wb_addr & ADDR_MASK] <= wb_data_o;
+		4'b0001: bufwrite(32'hFFFFFF00, 7:0)
+		4'b0010: bufwrite(32'hFFFF00FF, 15:8)
+		4'b0011: bufwrite(32'hFFFF0000, 15:0)
+		4'b0100: bufwrite(32'hFF00FFFF, 23:16)
+		4'b1000: bufwrite(32'h00FFFFFF, 31:24)
+		4'b1100: bufwrite(32'h0000FFFF, 31:16)
+		default: mem_ready <= 1;
+		endcase
+	end
+else if (!wb_stb) begin
+	wb_ack <= 0;
+end
+
+endmodule
diff --git a/gateware/soc.py b/gateware/soc.py
index ec5537f..19e9216 100644
--- a/gateware/soc.py
+++ b/gateware/soc.py
@@ -216,6 +216,9 @@ class _CRG(Module):
             self.submodules.idelayctrl = S7IDELAYCTRL(self.cd_idelay)
 
 class UpsilonSoC(SoCCore):
+    def add_bram(self, region_name):
+        self.bus.add_region(region_name, SoCRegion(0x2000, cached=False))
+        
     def __init__(self, variant):
         sys_clk_freq = int(100e6)
         platform = board_spec.Platform(variant=variant, toolchain="f4pga")
@@ -247,6 +250,7 @@ class UpsilonSoC(SoCCore):
         platform.add_source("rtl/control_loop/control_loop.v")
 #       platform.add_source("rtl/waveform/bram_interface_preprocessed.v")
 #       platform.add_source("rtl/waveform/waveform_preprocessed.v")
+        platform.add_source("rtl/bram/bram_preprocessed.v")
         platform.add_source("rtl/base/base.v")
 
         # SoCCore does not have sane defaults (no integrated rom)
@@ -289,6 +293,8 @@ class UpsilonSoC(SoCCore):
             pads       = platform.request("eth"))
         self.add_ethernet(phy=self.ethphy, dynamic_ip=True)
 
+        self.add_bram("BRAM0")
+
         platform.add_extension(io)
         self.submodules.base = Base(ClockSignal(), self.sdram, platform)