109 строки
2.1 KiB
C
109 строки
2.1 KiB
C
/*
|
|
* 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/timex.h>
|
|
#include <linux/preempt.h>
|
|
#include <linux/delay.h>
|
|
#include <linux/init.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 __devinit 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);
|