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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * Copyright (C) 1995-2004 Russell King
3 *
4 * Delay routines, using a pre-computed "loops_per_second" value.
5 */
6#ifndef __ASM_ARM_DELAY_H
7#define __ASM_ARM_DELAY_H
8
Peter Teichmann6d4518d2006-03-20 17:10:09 +00009#include <asm/param.h> /* HZ */
10
Linus Torvalds1da177e2005-04-16 15:20:36 -070011extern void __delay(int loops);
12
13/*
14 * This function intentionally does not exist; if you see references to
15 * it, it means that you're calling udelay() with an out of range value.
16 *
17 * With currently imposed limits, this means that we support a max delay
Peter Teichmann6d4518d2006-03-20 17:10:09 +000018 * of 2000us. Further limits: HZ<=1000 and bogomips<=3355
Linus Torvalds1da177e2005-04-16 15:20:36 -070019 */
20extern void __bad_udelay(void);
21
22/*
23 * division by multiplication: you don't have to worry about
24 * loss of precision.
25 *
26 * Use only for very small delays ( < 1 msec). Should probably use a
27 * lookup table, really, as the multiplications take much too long with
28 * short delays. This is a "reasonable" implementation, though (and the
29 * first constant multiplications gets optimized away if the delay is
30 * a constant)
31 */
32extern void __udelay(unsigned long usecs);
33extern void __const_udelay(unsigned long);
34
35#define MAX_UDELAY_MS 2
36
Peter Teichmann6d4518d2006-03-20 17:10:09 +000037#define udelay(n) \
38 (__builtin_constant_p(n) ? \
39 ((n) > (MAX_UDELAY_MS * 1000) ? __bad_udelay() : \
40 __const_udelay((n) * ((2199023U*HZ)>>11))) : \
Linus Torvalds1da177e2005-04-16 15:20:36 -070041 __udelay(n))
42
43#endif /* defined(_ARM_DELAY_H) */
44