Viewing file:  delay.c (1.5 KB) -rw-r--r--
Select action/file-type:
 (+) |  (+) |  (+) | Code (+) | Session (+) |  (+) | SDB (+) |  (+) |  (+) |  (+) |  (+) |  (+) |
/*
* 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/config.h>
#include <linux/sched.h>
#include <linux/delay.h>
#include <asm/processor.h>
#include <asm/delay.h>
#ifdef CONFIG_SMP
#include <asm/smp.h>
#endif
int x86_udelay_tsc = 0; /* Delay via TSC */
/*
* Do a udelay using the TSC for any CPU that happens
* to have one that we trust.
*/
static void __rdtsc_delay(unsigned long loops)
{
unsigned long bclock, now;
rdtscl(bclock);
do
{
rep_nop();
rdtscl(now);
} while ((now-bclock) < loops);
}
/*
* Non TSC based delay loop for 386, 486, MediaGX
*/
static void __loop_delay(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));
}
void __delay(unsigned long loops)
{
if (x86_udelay_tsc)
__rdtsc_delay(loops);
else
__loop_delay(loops);
}
inline void __const_udelay(unsigned long xloops)
{
int d0;
__asm__("mull %0"
:"=d" (xloops), "=&a" (d0)
:"1" (xloops),"0" (current_cpu_data.loops_per_jiffy));
__delay(xloops * HZ);
}
void __udelay(unsigned long usecs)
{
__const_udelay(usecs * 0x000010c6); /* 2**32 / 1000000 */
}
|