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
22void
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}
34EXPORT_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
42void
43udelay(unsigned long usecs)
44{
45	usecs *= (((unsigned long)HZ << 32) / 1000000) * LPJ;
46	__delay((long)usecs >> 32);
47}
48EXPORT_SYMBOL(udelay);
49
50void
51ndelay(unsigned long nsecs)
52{
53	nsecs *= (((unsigned long)HZ << 32) / 1000000000) * LPJ;
54	__delay((long)nsecs >> 32);
55}
56EXPORT_SYMBOL(ndelay);
57