From 9a9eec6c149c98f14df3678c7ccefbef633a62b7 Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Wed, 21 Jun 2000 00:00:00 +0000
Subject: [PATCH] Plan 9 from Bell Labs 2000-06-21

---
 pc/fns.h   |  1 +
 pc/i8253.c |  9 ++++++++-
 port/tod.c | 12 ++++++------
 3 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/pc/fns.h b/pc/fns.h
index 4fa350c26c11f6b1bac7107c14b7850b23dfe281..bc16f44acde74b8b3c0e794a3ee3043f3f112fe8 100644
--- a/pc/fns.h
+++ b/pc/fns.h
@@ -59,6 +59,7 @@ void	kbdinit(void);
 void	lgdt(ushort[3]);
 void	lidt(ushort[3]);
 void	links(void);
+void	loopbackintr(void);
 void	ltr(ulong);
 void	mathinit(void);
 void	meminit(ulong);
diff --git a/pc/i8253.c b/pc/i8253.c
index 4e87537bac684d96367fdb896a69eefd0b50bb87..6ae80cf3d8fda27d31e2f86f3e966aa7de829a33 100644
--- a/pc/i8253.c
+++ b/pc/i8253.c
@@ -124,10 +124,17 @@ i8253init(int aalcycles, int havecycleclock)
 	}
 }
 
+static void
+clockintr0(Ureg* ureg, void *v)
+{
+	loopbackintr();
+	clockintr(ureg, v);
+}
+
 void
 i8253enable(void)
 {
-	intrenable(IrqCLOCK, clockintr, 0, BUSUNKNOWN, "clock");
+	intrenable(IrqCLOCK, clockintr0, 0, BUSUNKNOWN, "clock");
 }
 
 /*
diff --git a/port/tod.c b/port/tod.c
index 9b7b1b4bee3a7032a8ced2938ab050db7b91cf42..85b42ceb8ce255a8766bfc298c5c0ac9d7a88736 100644
--- a/port/tod.c
+++ b/port/tod.c
@@ -141,18 +141,18 @@ todget(vlong *ticksp)
 }
 
 //
-//  called every clock tick
+//  called every clock tick to avoid calculation overflows
 //
 void
 todfix(void)
 {
-	static ulong last;
+	vlong ticks, diff;
+
+	ticks = fastticks(nil);
 
-	// once a second, make sure we don't overflow
-	if(MACHP(0)->ticks - last >= HZ){
-		last = MACHP(0)->ticks;
+	diff = ticks - tod.last;
+	if(diff > tod.hz)
 		todget(nil);
-	}
 }
 
 long