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/*
* Precise Delay Loops for i386
*
* Copyright (C) 1993 Linus Torvalds
* Copyright (C) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
*
* The __delay function must _NOT_ be inlined as its execution time
* depends wildly on alignment on many x86 processors. The additional
* jump magic is needed to get the timing stable on all the CPU's
* we have to worry about.
*/
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/preempt.h>
#include <linux/delay.h>
#include <asm/processor.h>
#include <asm/delay.h>
#include <asm/timer.h>
#ifdef CONFIG_SMP
# include <asm/smp.h>
#endif
/* simple loop based delay: */
static void delay_loop(unsigned long loops)
{
int d0;
__asm__ __volatile__(
"\tjmp 1f\n"
".align 16\n"
"1:\tjmp 2f\n"
".align 16\n"
"2:\tdecl %0\n\tjns 2b"
:"=&a" (d0)
:"0" (loops));
}
/* TSC based delay: */
static void delay_tsc(unsigned long loops)
{
unsigned long bclock, now;
preempt_disable(); /* TSC's are per-cpu */
rdtscl(bclock);
do {
rep_nop();
rdtscl(now);
} while ((now-bclock) < loops);
preempt_enable();
}
/*
* Since we calibrate only once at boot, this
* function should be set once at boot and not changed
*/
static void (*delay_fn)(unsigned long) = delay_loop;
void use_tsc_delay(void)
{
delay_fn = delay_tsc;
}
int read_current_timer(unsigned long *timer_val)
{
if (delay_fn == delay_tsc) {
rdtscl(*timer_val);
return 0;
}
return -1;
}
void __delay(unsigned long loops)
{
delay_fn(loops);
}
inline void __const_udelay(unsigned long xloops)
{
int d0;
xloops *= 4;
__asm__("mull %0"
:"=d" (xloops), "=&a" (d0)
:"1" (xloops), "0"
(cpu_data(raw_smp_processor_id()).loops_per_jiffy * (HZ/4)));
__delay(++xloops);
}
void __udelay(unsigned long usecs)
{
__const_udelay(usecs * 0x000010c7); /* 2**32 / 1000000 (rounded up) */
}
void __ndelay(unsigned long nsecs)
{
__const_udelay(nsecs * 0x00005); /* 2**32 / 1000000000 (rounded up) */
}
EXPORT_SYMBOL(__delay);
EXPORT_SYMBOL(__const_udelay);
EXPORT_SYMBOL(__udelay);
EXPORT_SYMBOL(__ndelay);
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