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/* calibrate.c: default delay calibration
*
* Excised from init/main.c
* Copyright (C) 1991, 1992 Linus Torvalds
*/
#include <linux/sched.h>
#include <linux/delay.h>
#include <linux/init.h>
static unsigned long preset_lpj;
static int __init lpj_setup(char *str)
{
preset_lpj = simple_strtoul(str,NULL,0);
return 1;
}
__setup("lpj=", lpj_setup);
/*
* This is the number of bits of precision for the loops_per_jiffy. Each
* bit takes on average 1.5/HZ seconds. This (like the original) is a little
* better than 1%
*/
#define LPS_PREC 8
void __devinit calibrate_delay(void)
{
unsigned long ticks, loopbit;
int lps_precision = LPS_PREC;
if (preset_lpj) {
loops_per_jiffy = preset_lpj;
printk("Calibrating delay loop (skipped)... "
"%lu.%02lu BogoMIPS preset\n",
loops_per_jiffy/(500000/HZ),
(loops_per_jiffy/(5000/HZ)) % 100);
} else {
loops_per_jiffy = (1<<12);
printk(KERN_DEBUG "Calibrating delay loop... ");
while ((loops_per_jiffy <<= 1) != 0) {
/* wait for "start of" clock tick */
ticks = jiffies;
while (ticks == jiffies)
/* nothing */;
/* Go .. */
ticks = jiffies;
__delay(loops_per_jiffy);
ticks = jiffies - ticks;
if (ticks)
break;
}
/*
* Do a binary approximation to get loops_per_jiffy set to
* equal one clock (up to lps_precision bits)
*/
loops_per_jiffy >>= 1;
loopbit = loops_per_jiffy;
while (lps_precision-- && (loopbit >>= 1)) {
loops_per_jiffy |= loopbit;
ticks = jiffies;
while (ticks == jiffies)
/* nothing */;
ticks = jiffies;
__delay(loops_per_jiffy);
if (jiffies != ticks) /* longer than 1 tick */
loops_per_jiffy &= ~loopbit;
}
/* Round the value and print it */
printk("%lu.%02lu BogoMIPS (lpj=%lu)\n",
loops_per_jiffy/(500000/HZ),
(loops_per_jiffy/(5000/HZ)) % 100,
loops_per_jiffy);
}
}
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