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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * Copyright (C) 1993, 2000 Linus Torvalds
3 *
4 * Delay routines, using a pre-computed "loops_per_jiffy" value.
5 */
6
Linus Torvalds1da177e2005-04-16 15:20:36 -07007#include <linux/module.h>
8#include <linux/sched.h> /* for udelay's use of smp_processor_id */
9#include <asm/param.h>
10#include <asm/smp.h>
11#include <linux/delay.h>
12
13/*
14 * Use only for very small delays (< 1 msec).
15 *
16 * The active part of our cycle counter is only 32-bits wide, and
17 * we're treating the difference between two marks as signed. On
18 * a 1GHz box, that's about 2 seconds.
19 */
20
21void
22__delay(int loops)
23{
24 int tmp;
25 __asm__ __volatile__(
26 " rpcc %0\n"
27 " addl %1,%0,%1\n"
28 "1: rpcc %0\n"
29 " subl %1,%0,%0\n"
30 " bgt %0,1b"
31 : "=&r" (tmp), "=r" (loops) : "1"(loops));
32}
Sudip Mukherjee14b97de2015-09-17 16:01:49 -070033EXPORT_SYMBOL(__delay);
Linus Torvalds1da177e2005-04-16 15:20:36 -070034
35#ifdef CONFIG_SMP
36#define LPJ cpu_data[smp_processor_id()].loops_per_jiffy
37#else
38#define LPJ loops_per_jiffy
39#endif
40
41void
42udelay(unsigned long usecs)
43{
44 usecs *= (((unsigned long)HZ << 32) / 1000000) * LPJ;
45 __delay((long)usecs >> 32);
46}
47EXPORT_SYMBOL(udelay);
48
49void
50ndelay(unsigned long nsecs)
51{
52 nsecs *= (((unsigned long)HZ << 32) / 1000000000) * LPJ;
53 __delay((long)nsecs >> 32);
54}
55EXPORT_SYMBOL(ndelay);