171 строка
3.1 KiB
C
171 строка
3.1 KiB
C
/*
|
|
* Smp timebase synchronization for ppc.
|
|
*
|
|
* Copyright (C) 2003 Samuel Rydh (samuel@ibrium.se)
|
|
*
|
|
*/
|
|
|
|
#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;
|
|
}
|