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);
59unsigned long calibrate_delay_is_known(void);
60void __attribute__((weak)) calibration_delay_done(void);
61void msleep(unsigned int msecs);
62unsigned long msleep_interruptible(unsigned int msecs);
63void usleep_range_state(unsigned long min, unsigned long max,
64 unsigned int state);
65
66static inline void usleep_range(unsigned long min, unsigned long max)
67{
68 usleep_range_state(min, max, TASK_UNINTERRUPTIBLE);
69}
70
71static inline void usleep_idle_range(unsigned long min, unsigned long max)
72{
73 usleep_range_state(min, max, TASK_IDLE);
74}
75
76static inline void ssleep(unsigned int seconds)
77{
78 msleep(msecs: seconds * 1000);
79}
80
81/* see Documentation/timers/timers-howto.rst for the thresholds */
82static inline void fsleep(unsigned long usecs)
83{
84 if (usecs <= 10)
85 udelay(usecs);
86 else if (usecs <= 20000)
87 usleep_range(min: usecs, max: 2 * usecs);
88 else
89 msleep(DIV_ROUND_UP(usecs, 1000));
90}
91
92#endif /* defined(_LINUX_DELAY_H) */
93

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