1 // SPDX-License-Identifier: GPL-2.0
2 /*
3 * Copyright (C) 1993, 2000 Linus Torvalds
4 *
5 * Delay routines, using a pre-computed "loops_per_jiffy" value.
6 */
7
8 #include <linux/module.h>
9 #include <linux/sched.h> /* for udelay's use of smp_processor_id */
10 #include <asm/param.h>
11 #include <asm/smp.h>
12 #include <linux/delay.h>
13
14 /*
15 * Use only for very small delays (< 1 msec).
16 *
17 * The active part of our cycle counter is only 32-bits wide, and
18 * we're treating the difference between two marks as signed. On
19 * a 1GHz box, that's about 2 seconds.
20 */
21
22 void
23 __delay(int loops)
24 {
25 int tmp;
26 __asm__ __volatile__(
27 " rpcc %0\n"
28 " addl %1,%0,%1\n"
29 "1: rpcc %0\n"
30 " subl %1,%0,%0\n"
31 " bgt %0,1b"
32 : "=&r" (tmp), "=r" (loops) : "1"(loops));
33 }
34 EXPORT_SYMBOL(__delay);
35
36 #ifdef CONFIG_SMP
37 #define LPJ cpu_data[smp_processor_id()].loops_per_jiffy
38 #else
39 #define LPJ loops_per_jiffy
40 #endif
41
42 void
43 udelay(unsigned long usecs)
44 {
45 usecs *= (((unsigned long)HZ << 32) / 1000000) * LPJ;
46 __delay((long)usecs >> 32);
47 }
48 EXPORT_SYMBOL(udelay);
49
50 void
51 ndelay(unsigned long nsecs)
52 {
53 nsecs *= (((unsigned long)HZ << 32) / 1000000000) * LPJ;
54 __delay((long)nsecs >> 32);
55 }
56 EXPORT_SYMBOL(ndelay);
57
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