From 07de394ddb3438637d4038114d34a2048b448017 Mon Sep 17 00:00:00 2001
From: David Anderson <dave@natulte.net>
Date: Mon, 9 Sep 2024 12:47:19 -0700
Subject: [PATCH] lib/PinSync: use an explicit type

To make them more obviously not normal registers, and to add
annotations to make the scheduling more annoying if you try
holding them wrong.
---
 lib/PinSync.bsv      | 8 +++++++-
 lib/PinSync_Test.bsv | 2 +-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/lib/PinSync.bsv b/lib/PinSync.bsv
index a7db442..9b50f84 100644
--- a/lib/PinSync.bsv
+++ b/lib/PinSync.bsv
@@ -1,5 +1,11 @@
 package PinSync;
 
+(* always_ready, always_enabled *)
+interface PinSync#(type val);
+   method Action _write(val a);
+   method val _read();
+endinterface
+
 // mkPinSync builds a synchronizer for use with asynchronous inputs.
 //
 // You should only use this to capture asynchronous inputs coming from
@@ -18,7 +24,7 @@ package PinSync;
 // source domain. Conceptually, we assume that register exists outside
 // our design and is driving the input of mkPinSync, so we just need
 // the metastability mitigation within our own domain.
-module mkPinSync(val init_value, Reg#(val) ifc)
+module mkPinSync(val init_value, PinSync#(val) ifc)
    provisos(Bits#(val, _));
 
    Reg#(val) r1 <- mkReg(init_value);
diff --git a/lib/PinSync_Test.bsv b/lib/PinSync_Test.bsv
index 37fec83..6052e88 100644
--- a/lib/PinSync_Test.bsv
+++ b/lib/PinSync_Test.bsv
@@ -10,7 +10,7 @@ module mkTB();
    let testflags <- mkTestFlags();
    let cycles <- mkCycleCounter();
 
-   Reg#(UInt#(2)) dut <- mkPinSync(0);
+   PinSync#(UInt#(2)) dut <- mkPinSync(0);
 
    function Action check_dut_val(UInt#(2) want_val);
       return action