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udelay.c
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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
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
41 udelay(unsigned long usecs)
42 {
43  usecs *= (((unsigned long)HZ << 32) / 1000000) * LPJ;
44  __delay((long)usecs >> 32);
45 }
47 
48 void
49 ndelay(unsigned long nsecs)
50 {
51  nsecs *= (((unsigned long)HZ << 32) / 1000000000) * LPJ;
52  __delay((long)nsecs >> 32);
53 }