Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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linux
1#ifdef __KERNEL__
2#ifndef _PPC_DELAY_H
3#define _PPC_DELAY_H
4
5#include <asm/param.h>
6
7/*
8 * Copyright 1996, Paul Mackerras.
9 *
10 * This program is free software; you can redistribute it and/or
11 * modify it under the terms of the GNU General Public License
12 * as published by the Free Software Foundation; either version
13 * 2 of the License, or (at your option) any later version.
14 */
15
16extern unsigned long loops_per_jiffy;
17
18extern void __delay(unsigned int loops);
19
20/*
21 * Note that 19 * 226 == 4294 ==~ 2^32 / 10^6, so
22 * loops = (4294 * usecs * loops_per_jiffy * HZ) / 2^32.
23 *
24 * The mulhwu instruction gives us loops = (a * b) / 2^32.
25 * We choose a = usecs * 19 * HZ and b = loops_per_jiffy * 226
26 * because this lets us support a wide range of HZ and
27 * loops_per_jiffy values without either a or b overflowing 2^32.
28 * Thus we need usecs * HZ <= (2^32 - 1) / 19 = 226050910 and
29 * loops_per_jiffy <= (2^32 - 1) / 226 = 19004280
30 * (which corresponds to ~3800 bogomips at HZ = 100).
31 * -- paulus
32 */
33#define __MAX_UDELAY (226050910UL/HZ) /* maximum udelay argument */
34#define __MAX_NDELAY (4294967295UL/HZ) /* maximum ndelay argument */
35
36extern __inline__ void __udelay(unsigned int x)
37{
38 unsigned int loops;
39
40 __asm__("mulhwu %0,%1,%2" : "=r" (loops) :
41 "r" (x), "r" (loops_per_jiffy * 226));
42 __delay(loops);
43}
44
45extern __inline__ void __ndelay(unsigned int x)
46{
47 unsigned int loops;
48
49 __asm__("mulhwu %0,%1,%2" : "=r" (loops) :
50 "r" (x), "r" (loops_per_jiffy * 5));
51 __delay(loops);
52}
53
54extern void __bad_udelay(void); /* deliberately undefined */
55extern void __bad_ndelay(void); /* deliberately undefined */
56
57#define udelay(n) (__builtin_constant_p(n)? \
58 ((n) > __MAX_UDELAY? __bad_udelay(): __udelay((n) * (19 * HZ))) : \
59 __udelay((n) * (19 * HZ)))
60
61#define ndelay(n) (__builtin_constant_p(n)? \
62 ((n) > __MAX_NDELAY? __bad_ndelay(): __ndelay((n) * HZ)) : \
63 __ndelay((n) * HZ))
64
65#endif /* defined(_PPC_DELAY_H) */
66#endif /* __KERNEL__ */