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
__delay(int loops)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
udelay(unsigned long usecs)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
ndelay(unsigned long nsecs)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