From 90cd52144aabdfb896d09454208b445ac67d6034 Mon Sep 17 00:00:00 2001
From: David du Colombier <0intro@gmail.com>
Date: Thu, 16 Jul 1998 00:00:00 +0000
Subject: [PATCH] Plan 9 from Bell Labs 1998-07-16

---
 pc/apic.c        | 29 +++++++++++++++--------------
 pc/archgeneric.c |  1 +
 pc/dat.h         |  2 ++
 pc/mp.c          | 16 +++++++++-------
 pc/mp.h          |  4 ++--
 5 files changed, 29 insertions(+), 23 deletions(-)

diff --git a/pc/apic.c b/pc/apic.c
index 32ca62bbfdb2ded924dd8a7352cf3e5a05f0c131..6dcae1c3053c8aa8fe89a7d1a7ec5cf83b19ad9a 100644
--- a/pc/apic.c
+++ b/pc/apic.c
@@ -88,6 +88,7 @@ enum {					/* LapicTDCR */
 };
 
 static ulong* lapicbase;
+static int clkin;
 
 static int
 lapicr(int r)
@@ -104,7 +105,7 @@ lapicw(int r, int data)
 }
 
 void
-lapiconline(int clkin)
+lapiconline(void)
 {
 	/*
 	 * Reload the timer to de-synchronise the processors,
@@ -118,7 +119,7 @@ lapiconline(int clkin)
 	lapicw(LapicTPR, 0);
 }
 
-static int
+static void
 lapictimerinit(void)
 {
 	ulong lo, v;
@@ -128,21 +129,23 @@ lapictimerinit(void)
 	lapicw(LapicTDCR, LapicX1);
 	lapicw(LapicTIMER, ApicIMASK|LapicCLKIN|LapicONESHOT|VectorTIMER);
 
-	lapicw(LapicTICR, v);
-	wrmsr(0x10, 0);
+	if(clkin == 0){
+		lapicw(LapicTICR, v);
+		wrmsr(0x10, 0);
 
-	do{
-		rdmsr(0x10, &tsc);
-		lo = (ulong)tsc;
-	}while(lo < v);
+		do{
+			rdmsr(0x10, &tsc);
+			lo = (ulong)tsc;
+		}while(lo < v);
 
-	return ((v-lapicr(LapicTCCR)+500)/1000)*1000*1000;
+		clkin = ((v-lapicr(LapicTCCR)+500)/1000)*1000*1000;
+	}
 }
 
-int
+void
 lapicinit(Apic* apic)
 {
-	ulong clkin, r, lvt;
+	ulong r, lvt;
 
 	if(lapicbase == 0)
 		lapicbase = apic->addr;
@@ -153,7 +156,7 @@ lapicinit(Apic* apic)
 	lapicw(LapicTPR, 0xFF);
 	lapicw(LapicSVR, LapicENABLE|VectorSPURIOUS);
 
-	clkin = lapictimerinit();
+	lapictimerinit();
 
 	/*
 	 * Some Pentium revisions have a bug whereby spurious
@@ -200,8 +203,6 @@ lapicinit(Apic* apic)
 	 * interrupts.
 	lapicw(LapicTPR, 0);
 	 */
-
-	return clkin;
 }
 
 void
diff --git a/pc/archgeneric.c b/pc/archgeneric.c
index 561b33b13e17505b3734354bd5a3f63d33002a4b..657dd3b53315ca4f3e157706fcddbec536993046 100644
--- a/pc/archgeneric.c
+++ b/pc/archgeneric.c
@@ -210,6 +210,7 @@ static uvlong fasthz;
 void
 cycletimerinit(void)
 {
+	wrmsr(0x10, 0);
 	fasthz = 1000000LL*m->cpumhz;
 }
 
diff --git a/pc/dat.h b/pc/dat.h
index 957c2325564254d62c437a7a139e1d431f624d50..f91e4d7cabd7d6faa8862738df29956650633a48 100644
--- a/pc/dat.h
+++ b/pc/dat.h
@@ -187,6 +187,8 @@ struct Mach
 	vlong	mtrrfix[11];
 	vlong	mtrrvar[32];		/* 256 max. */
 
+	vlong	clockstart;		/* starting value for cycle clock */
+
 	int	stack[1];
 };
 
diff --git a/pc/mp.c b/pc/mp.c
index d7f89cd52df44ec2498c14d218a30397af596f13..967afdaaeb7525f725a9fe9ca8c83070702489e0 100644
--- a/pc/mp.c
+++ b/pc/mp.c
@@ -354,9 +354,11 @@ checkmtrr(void)
 static void
 squidboy(Apic* apic)
 {
-	int clkin;
-
 //	iprint("Hello Squidboy\n");
+
+	/* synchronize cycle clocks */
+	wrmsr(0x10, m->clockstart);
+
 	machinit();
 	mmuinit();
 
@@ -374,8 +376,8 @@ squidboy(Apic* apic)
 	while(MACHP(0)->ticks == 0)
 		;
 
-	clkin = lapicinit(apic);
-	lapiconline(clkin);
+	lapicinit(apic);
+	lapiconline();
 
 	lock(&active);
 	active.machs |= 1<<m->machno;
@@ -441,6 +443,7 @@ mpstartap(Apic* apic)
 	*p = i>>8;
 
 	nvramwrite(0x0F, 0x0A);
+	rdmsr(0x10, &mach->clockstart);
 	lapicstartap(apic, PADDR(APBOOTSTRAP));
 	for(i = 0; i < 100000; i++){
 		lock(&mprdthilock);
@@ -460,7 +463,6 @@ mpinit(void)
 	PCMP *pcmp;
 	uchar *e, *p;
 	Apic *apic, *bpapic;
-	int clkin;
 
 	i8259init();
 
@@ -529,7 +531,7 @@ mpinit(void)
 	if(bpapic == 0)
 		return;
 
-	clkin = lapicinit(bpapic);
+	lapicinit(bpapic);
 	lock(&mprdthilock);
 	mprdthi |= (1<<bpapic->apicno)<<24;
 	unlock(&mprdthilock);
@@ -542,7 +544,7 @@ mpinit(void)
 	intrenable(VectorTIMER, clockintr, 0, BUSUNKNOWN);
 	intrenable(VectorERROR, lapicerror, 0, BUSUNKNOWN);
 	intrenable(VectorSPURIOUS, lapicspurious, 0, BUSUNKNOWN);
-	lapiconline(clkin);
+	lapiconline();
 
 	checkmtrr();
 
diff --git a/pc/mp.h b/pc/mp.h
index f387548ffcef9e60881d68a3d5b3a2d9cf2de69e..8419892b58cfc735473df1a2dacb0e274325b2fe 100644
--- a/pc/mp.h
+++ b/pc/mp.h
@@ -210,8 +210,8 @@ enum {
 extern void ioapicrdtr(Apic*, int, int*, int*);
 extern void ioapicrdtw(Apic*, int, int, int);
 extern void ioapicinit(Apic*, int);
-extern void lapiconline(int);
-extern int lapicinit(Apic*);
+extern void lapiconline(void);
+extern void lapicinit(Apic*);
 extern void lapicstartap(Apic*, int);
 extern void lapicerror(Ureg*, void*);
 extern void lapicspurious(Ureg*, void*);