powerpc: Merge smp-tbsync.c (the generic timebase sync routine)
Signed-off-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/powerpc/kernel/smp-tbsync.c b/arch/powerpc/kernel/smp-tbsync.c
new file mode 100644
index 0000000..9adef3b
--- /dev/null
+++ b/arch/powerpc/kernel/smp-tbsync.c
@@ -0,0 +1,171 @@
+/*
+ * 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 u64 tb;
+ volatile u64 mark;
+ volatile int cmd;
+ volatile int handshake;
+ int filler[2];
+
+ volatile int ack;
+ int filler2[7];
+
+ volatile int race_result;
+} *tbsync;
+
+static volatile int running;
+
+static void __devinit enter_contest(u64 mark, long add)
+{
+ while (get_tb() < mark)
+ tbsync->race_result = add;
+}
+
+void __devinit smp_generic_take_timebase(void)
+{
+ int cmd;
+ u64 tb;
+
+ local_irq_disable();
+ while (!running)
+ barrier();
+ rmb();
+
+ for (;;) {
+ tbsync->ack = 1;
+ while (!tbsync->handshake)
+ barrier();
+ rmb();
+
+ cmd = tbsync->cmd;
+ tb = tbsync->tb;
+ mb();
+ tbsync->ack = 0;
+ if (cmd == kExit)
+ break;
+
+ while (tbsync->handshake)
+ barrier();
+ if (cmd == kSetAndTest)
+ set_tb(tb >> 32, tb & 0xfffffffful);
+ enter_contest(tbsync->mark, -1);
+ }
+ local_irq_enable();
+}
+
+static int __devinit start_contest(int cmd, long offset, int num)
+{
+ int i, score=0;
+ u64 tb;
+ long mark;
+
+ tbsync->cmd = cmd;
+
+ local_irq_disable();
+ for (i = -3; i < num; ) {
+ tb = get_tb() + 400;
+ tbsync->tb = tb + offset;
+ tbsync->mark = mark = tb + 400;
+
+ wmb();
+
+ tbsync->handshake = 1;
+ while (tbsync->ack)
+ barrier();
+
+ while (get_tb() <= tb)
+ barrier();
+ tbsync->handshake = 0;
+ enter_contest(mark, 1);
+
+ while (!tbsync->ack)
+ barrier();
+
+ 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)
+ barrier();
+
+ 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)
+ barrier();
+ tbsync->handshake = 0;
+ kfree(tbsync);
+ tbsync = NULL;
+ running = 0;
+}