1 /*
2 * Copyright (C) 1993, 2000 Linus Torvalds
3 *
4 * Delay routines, using a pre-computed "loops_per_jiffy" value.
5 */
6
7 #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
21 void
__delay(int loops)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 }
33
34 #ifdef CONFIG_SMP
35 #define LPJ cpu_data[smp_processor_id()].loops_per_jiffy
36 #else
37 #define LPJ loops_per_jiffy
38 #endif
39
40 void
udelay(unsigned long usecs)41 udelay(unsigned long usecs)
42 {
43 usecs *= (((unsigned long)HZ << 32) / 1000000) * LPJ;
44 __delay((long)usecs >> 32);
45 }
46 EXPORT_SYMBOL(udelay);
47
48 void
ndelay(unsigned long nsecs)49 ndelay(unsigned long nsecs)
50 {
51 nsecs *= (((unsigned long)HZ << 32) / 1000000000) * LPJ;
52 __delay((long)nsecs >> 32);
53 }
54 EXPORT_SYMBOL(ndelay);
55