1 files changed, 179 insertions, 0 deletions
diff --git a/arch/ppc64/kernel/smp-tbsync.c b/arch/ppc64/kernel/smp-tbsync.c
new file mode 100644
index 00000000000..7d8ec9996b3
--- /dev/null
+++ b/arch/ppc64/kernel/smp-tbsync.c
@@ -0,0 +1,179 @@
+/*
+ * Smp timebase synchronization for ppc.
+ *
+ * Copyright (C) 2003 Samuel Rydh (samuel@ibrium.se)
+ *
+ */
+
+#include <linux/config.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/smp.h>
+#include <linux/unistd.h>
+#include <linux/init.h>
+#include <asm/atomic.h>
+#include <asm/smp.h>
+#include <asm/time.h>
+
+#define NUM_ITER		300
+
+enum {
+	kExit=0, kSetAndTest, kTest
+};
+
+static struct {
+	volatile long		tb;
+	volatile long		mark;
+	volatile int		cmd;
+	volatile int		handshake;
+	int			filler[3];
+
+	volatile int		ack;
+	int			filler2[7];
+
+	volatile int		race_result;
+} *tbsync;
+
+static volatile int		running;
+
+static void __devinit
+enter_contest( long mark, long add )
+{
+	while( (long)(mftb() - mark) < 0 )
+		tbsync->race_result = add;
+}
+
+void __devinit
+smp_generic_take_timebase( void )
+{
+	int cmd;
+	long tb;
+
+	local_irq_disable();
+	while( !running )
+		;
+	rmb();
+
+	for( ;; ) {
+		tbsync->ack = 1;
+		while( !tbsync->handshake )
+			;
+		rmb();
+
+		cmd = tbsync->cmd;
+		tb = tbsync->tb;
+		tbsync->ack = 0;
+		if( cmd == kExit )
+			return;
+
+		if( cmd == kSetAndTest ) {
+			while( tbsync->handshake )
+				;
+			asm volatile ("mttbl %0" :: "r" (tb & 0xfffffffful) );
+			asm volatile ("mttbu %0" :: "r" (tb >> 32) );
+		} else {
+			while( tbsync->handshake )
+				;
+		}
+		enter_contest( tbsync->mark, -1 );
+	}
+	local_irq_enable();
+}
+
+static int __devinit
+start_contest( int cmd, long offset, long num )
+{
+	int i, score=0;
+	long tb, mark;
+
+	tbsync->cmd = cmd;
+
+	local_irq_disable();
+	for( i=-3; i<num; ) {
+		tb = (long)mftb() + 400;
+		tbsync->tb = tb + offset;
+		tbsync->mark = mark = tb + 400;
+
+		wmb();
+
+		tbsync->handshake = 1;
+		while( tbsync->ack )
+			;
+
+		while( (long)(mftb() - tb) <= 0 )
+			;
+		tbsync->handshake = 0;
+		enter_contest( mark, 1 );
+
+		while( !tbsync->ack )
+			;
+
+	       	if ((tbsync->tb ^ (long)mftb()) & 0x8000000000000000ul)
+			continue;
+		if( i++ > 0 )
+			score += tbsync->race_result;
+	}
+	local_irq_enable();
+	return score;
+}
+
+void __devinit
+smp_generic_give_timebase( void )
+{
+	int i, score, score2, old, min=0, max=5000, offset=1000;
+
+	printk("Synchronizing timebase\n");
+
+	/* if this fails then this kernel won't work anyway... */
+	tbsync = kmalloc( sizeof(*tbsync), GFP_KERNEL );
+	memset( tbsync, 0, sizeof(*tbsync) );
+	mb();
+	running = 1;
+
+	while( !tbsync->ack )
+		;
+
+	printk("Got ack\n");
+
+	/* binary search */
+	for( old=-1 ; old != offset ; offset=(min+max)/2 ) {
+		score = start_contest( kSetAndTest, offset, NUM_ITER );
+
+		printk("score %d, offset %d\n", score, offset );
+
+		if( score > 0 )
+			max = offset;
+		else
+			min = offset;
+		old = offset;
+	}
+	score = start_contest( kSetAndTest, min, NUM_ITER );
+	score2 = start_contest( kSetAndTest, max, NUM_ITER );
+
+	printk( "Min %d (score %d), Max %d (score %d)\n", min, score, max, score2 );
+	score = abs( score );
+	score2 = abs( score2 );
+	offset = (score < score2) ? min : max;
+
+	/* guard against inaccurate mttb */
+	for( i=0; i<10; i++ ) {
+		start_contest( kSetAndTest, offset, NUM_ITER/10 );
+
+		if( (score2=start_contest(kTest, offset, NUM_ITER)) < 0 )
+			score2 = -score2;
+		if( score2 <= score || score2 < 20 )
+			break;
+	}
+	printk("Final offset: %d (%d/%d)\n", offset, score2, NUM_ITER );
+
+	/* exiting */
+	tbsync->cmd = kExit;
+	wmb();
+	tbsync->handshake = 1;
+	while( tbsync->ack )
+		;
+	tbsync->handshake = 0;
+	kfree( tbsync );
+	tbsync = NULL;
+	running = 0;
+}