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 
25 extern 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
ndelay(unsigned long x)50 static inline void ndelay(unsigned long x)
51 {
52 	udelay(DIV_ROUND_UP(x, 1000));
53 }
54 #define ndelay(x) ndelay(x)
55 #endif
56 
57 extern unsigned long lpj_fine;
58 void calibrate_delay(void);
59 void __attribute__((weak)) calibration_delay_done(void);
60 void msleep(unsigned int msecs);
61 unsigned long msleep_interruptible(unsigned int msecs);
62 void usleep_range_state(unsigned long min, unsigned long max,
63 			unsigned int state);
64 
usleep_range(unsigned long min,unsigned long max)65 static inline void usleep_range(unsigned long min, unsigned long max)
66 {
67 	usleep_range_state(min, max, TASK_UNINTERRUPTIBLE);
68 }
69 
usleep_idle_range(unsigned long min,unsigned long max)70 static inline void usleep_idle_range(unsigned long min, unsigned long max)
71 {
72 	usleep_range_state(min, max, TASK_IDLE);
73 }
74 
ssleep(unsigned int seconds)75 static inline void ssleep(unsigned int seconds)
76 {
77 	msleep(seconds * 1000);
78 }
79 
80 /* see Documentation/timers/timers-howto.rst for the thresholds */
fsleep(unsigned long usecs)81 static 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