1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef _LINUX_DELAY_H
3#define _LINUX_DELAY_H
4
5/*
6 * Copyright (C) 1993 Linus Torvalds
7 *
8 * Delay routines, using a pre-computed "loops_per_jiffy" value.
9 *
10 * Please note that ndelay(), udelay() and mdelay() may return early for
11 * several reasons:
12 * 1. computed loops_per_jiffy too low (due to the time taken to
13 * execute the timer interrupt.)
14 * 2. cache behaviour affecting the time it takes to execute the
15 * loop function.
16 * 3. CPU clock rate changes.
17 *
18 * Please see this thread:
19 * https://lists.openwall.net/linux-kernel/2011/01/09/56
20 */
21
22#include <linux/math.h>
23#include <linux/sched.h>
24
25extern unsigned long loops_per_jiffy;
26
27#include <asm/delay.h>
28
29/*
30 * Using udelay() for intervals greater than a few milliseconds can
31 * risk overflow for high loops_per_jiffy (high bogomips) machines. The
32 * mdelay() provides a wrapper to prevent this. For delays greater
33 * than MAX_UDELAY_MS milliseconds, the wrapper is used. Architecture
34 * specific values can be defined in asm-???/delay.h as an override.
35 * The 2nd mdelay() definition ensures GCC will optimize away the
36 * while loop for the common cases where n <= MAX_UDELAY_MS -- Paul G.
37 */
38
39#ifndef MAX_UDELAY_MS
40#define MAX_UDELAY_MS 5
41#endif
42
43#ifndef mdelay
44#define mdelay(n) (\
45 (__builtin_constant_p(n) && (n)<=MAX_UDELAY_MS) ? udelay((n)*1000) : \
46 ({unsigned long __ms=(n); while (__ms--) udelay(1000);}))
47#endif
48
49#ifndef ndelay
50static inline void ndelay(unsigned long x)
51{
52 udelay(DIV_ROUND_UP(x, 1000));
53}
54#define ndelay(x) ndelay(x)
55#endif
56
57extern unsigned long lpj_fine;
58void calibrate_delay(void);
59void __attribute__((weak)) calibration_delay_done(void);
60void msleep(unsigned int msecs);
61unsigned long msleep_interruptible(unsigned int msecs);
62void usleep_range_state(unsigned long min, unsigned long max,
63 unsigned int state);
64
65static inline void usleep_range(unsigned long min, unsigned long max)
66{
67 usleep_range_state(min, max, TASK_UNINTERRUPTIBLE);
68}
69
70static inline void usleep_idle_range(unsigned long min, unsigned long max)
71{
72 usleep_range_state(min, max, TASK_IDLE);
73}
74
75static inline void ssleep(unsigned int seconds)
76{
77 msleep(seconds * 1000);
78}
79
80/* see Documentation/timers/timers-howto.rst for the thresholds */
81static inline void fsleep(unsigned long usecs)
82{
83 if (usecs <= 10)
84 udelay(usecs);
85 else if (usecs <= 20000)
86 usleep_range(usecs, 2 * usecs);
87 else
88 msleep(DIV_ROUND_UP(usecs, 1000));
89}
90
91#endif /* defined(_LINUX_DELAY_H) */
92

source code of linux/include/linux/delay.h