1/* SPDX-License-Identifier: GPL-2.0 */
2#ifndef __ASM_GENERIC_DELAY_H
3#define __ASM_GENERIC_DELAY_H
4
5/* Undefined functions to get compile-time errors */
6extern void __bad_udelay(void);
7extern void __bad_ndelay(void);
8
9extern void __udelay(unsigned long usecs);
10extern void __ndelay(unsigned long nsecs);
11extern void __const_udelay(unsigned long xloops);
12extern void __delay(unsigned long loops);
13
14/*
15 * The weird n/20000 thing suppresses a "comparison is always false due to
16 * limited range of data type" warning with non-const 8-bit arguments.
17 */
18
19/* 0x10c7 is 2**32 / 1000000 (rounded up) */
20#define udelay(n) \
21 ({ \
22 if (__builtin_constant_p(n)) { \
23 if ((n) / 20000 >= 1) \
24 __bad_udelay(); \
25 else \
26 __const_udelay((n) * 0x10c7ul); \
27 } else { \
28 __udelay(n); \
29 } \
30 })
31
32/* 0x5 is 2**32 / 1000000000 (rounded up) */
33#define ndelay(n) \
34 ({ \
35 if (__builtin_constant_p(n)) { \
36 if ((n) / 20000 >= 1) \
37 __bad_ndelay(); \
38 else \
39 __const_udelay((n) * 5ul); \
40 } else { \
41 __ndelay(n); \
42 } \
43 })
44
45#endif /* __ASM_GENERIC_DELAY_H */
46

source code of linux/include/asm-generic/delay.h