From 40c54e26c01b4f60f4a245134b74900ca6a50ee1 Mon Sep 17 00:00:00 2001
From: Byron Lathi <bslathi19@gmail.com>
Date: Wed, 15 Nov 2023 08:42:02 -0800
Subject: [PATCH] Demonstrate basic interrupt functionality

---
 .../simulation/tbs/interrupt_controller_tb.sv |  3 ++
 hw/efinix_fpga/src/interrupt_controller.sv    | 30 +++++++++++--------
 2 files changed, 20 insertions(+), 13 deletions(-)

diff --git a/hw/efinix_fpga/simulation/tbs/interrupt_controller_tb.sv b/hw/efinix_fpga/simulation/tbs/interrupt_controller_tb.sv
index 0f42817..b457ce2 100644
--- a/hw/efinix_fpga/simulation/tbs/interrupt_controller_tb.sv
+++ b/hw/efinix_fpga/simulation/tbs/interrupt_controller_tb.sv
@@ -81,6 +81,9 @@ initial begin
     @(posedge r_clk_cpu)
     int_in = 0;
     repeat (5) @(posedge r_clk_cpu);
+    write_reg(0, 8'hff);
+    write_reg(1, 8'h01);
+    repeat (5) @(posedge r_clk_cpu);
     $finish();
 end
 
diff --git a/hw/efinix_fpga/src/interrupt_controller.sv b/hw/efinix_fpga/src/interrupt_controller.sv
index 571619f..71b7885 100644
--- a/hw/efinix_fpga/src/interrupt_controller.sv
+++ b/hw/efinix_fpga/src/interrupt_controller.sv
@@ -66,10 +66,7 @@ logic w_eoi;
 logic [255:0] r_int, r_int_next;
 
 always_comb begin
-    r_int_next = (~r_int | w_type_full_data) & int_masked;
-    if (w_eoi) begin
-        r_int_next[irq_val] = 0;
-    end
+    w_eoi = 0;
 
     if (addr == '0 && we) begin
         cmd_next = i_data;
@@ -79,6 +76,7 @@ always_comb begin
 
 
     w_type_write = '0;
+    w_enable_write = '0;
 
     if (addr == '1) begin
         unique casez (cmd)
@@ -99,29 +97,35 @@ always_comb begin
             end
 
             8'hff: begin
-                $display("Not handled");
+                // Kind of dumb, still requires a data write
+                w_eoi = i_data[0] & we;
             end
         endcase
     end
 
     int_out = |r_int;
+
+    irq_val = 8'hff;
+    for (int i = 255; i >= 0; i--) begin
+        if (r_int[i] == 1) begin
+            irq_val = i;
+        end
+    end
+
+    r_int_next = (~r_int | w_type_full_data) & int_masked | r_int;
+    if (w_eoi) begin
+        r_int_next[irq_val] = 0;
+    end
 end
 
 always_ff @(negedge clk) begin
     if (reset) begin
         r_int <= '0;
+        cmd <= '0;
     end else begin
         r_int <= r_int_next;
         cmd <= cmd_next;
     end
 end
 
-always_comb begin
-    for (int i = 255; i == 0; i--) begin
-        if (r_int[i] == 1) begin
-            irq_val = i;
-        end
-    end
-end
-
 endmodule
\ No newline at end of file