181 строка
3.3 KiB
C
181 строка
3.3 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 int tbu;
|
|
volatile int tbl;
|
|
volatile int 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( int mark, int add )
|
|
{
|
|
while( (int)(get_tbl() - mark) < 0 )
|
|
tbsync->race_result = add;
|
|
}
|
|
|
|
void __devinit
|
|
smp_generic_take_timebase( void )
|
|
{
|
|
int cmd, tbl, tbu;
|
|
unsigned long flags;
|
|
|
|
local_irq_save(flags);
|
|
while( !running )
|
|
;
|
|
rmb();
|
|
|
|
for( ;; ) {
|
|
tbsync->ack = 1;
|
|
while( !tbsync->handshake )
|
|
;
|
|
rmb();
|
|
|
|
cmd = tbsync->cmd;
|
|
tbl = tbsync->tbl;
|
|
tbu = tbsync->tbu;
|
|
tbsync->ack = 0;
|
|
if( cmd == kExit )
|
|
break;
|
|
|
|
if( cmd == kSetAndTest ) {
|
|
while( tbsync->handshake )
|
|
;
|
|
asm volatile ("mttbl %0" :: "r" (tbl) );
|
|
asm volatile ("mttbu %0" :: "r" (tbu) );
|
|
} else {
|
|
while( tbsync->handshake )
|
|
;
|
|
}
|
|
enter_contest( tbsync->mark, -1 );
|
|
}
|
|
local_irq_restore(flags);
|
|
}
|
|
|
|
static int __devinit
|
|
start_contest( int cmd, int offset, int num )
|
|
{
|
|
int i, tbu, tbl, mark, score=0;
|
|
|
|
tbsync->cmd = cmd;
|
|
|
|
local_irq_disable();
|
|
for( i=-3; i<num; ) {
|
|
tbl = get_tbl() + 400;
|
|
tbsync->tbu = tbu = get_tbu();
|
|
tbsync->tbl = tbl + offset;
|
|
tbsync->mark = mark = tbl + 400;
|
|
|
|
wmb();
|
|
|
|
tbsync->handshake = 1;
|
|
while( tbsync->ack )
|
|
;
|
|
|
|
while( (int)(get_tbl() - tbl) <= 0 )
|
|
;
|
|
tbsync->handshake = 0;
|
|
enter_contest( mark, 1 );
|
|
|
|
while( !tbsync->ack )
|
|
;
|
|
|
|
if( tbsync->tbu != get_tbu() || ((tbsync->tbl ^ get_tbl()) & 0x80000000) )
|
|
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 = kzalloc( sizeof(*tbsync), GFP_KERNEL );
|
|
mb();
|
|
running = 1;
|
|
|
|
while( !tbsync->ack )
|
|
;
|
|
|
|
/* 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;
|
|
|
|
/* all done */
|
|
smp_tb_synchronized = 1;
|
|
}
|