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/*
 *  linux/include/asm-arm/delay.h
 *
 *  Copyright (C) 1995-2003 Russell King
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 *  Delay routines, using a pre-computed "loops_per_second" value.
 */
#ifndef __ASM_ARM_DELAY_H
#define __ASM_ARM_DELAY_H
 
/*
 * Division by multiplication and shifts.
 *
 *  We want the number of loops to complete, where loops is:
 *      (us * (HZ * loops_per_jiffy)) / 10^6
 *  or
 *      (ns * (HZ * loops_per_jiffy)) / 10^9
 *
 *  Since we don't want to do long division, we multiply both numerator
 *  and denominator by (2^28 / 10^6):
 *
 *      (us * (2^28 / 10^6) * HZ * loops_per_jiffy) / 2^28
 *
 *  =>  (us * (2^28 * HZ / 10^6) * loops_per_jiffy) / 2^28
 *
 *  ~>  (((us * (2^28 * HZ / 10^6)) / 2^11) * (loops_per_jiffy / 2^12)) / 2^5
 *         (for large loops_per_jiffy >> 2^12)
 *
 *  Note: maximum loops_per_jiffy = 67108863 (bogomips = 1342.18)
 *        minimum loops_per_jiffy = 20000 (bogomips = 0.4)
 *
 * Note: we rely on HZ = 100.
 */
#define UDELAY_FACTOR   26843
#define NDELAY_FACTOR   27
 
#ifndef __ASSEMBLY__
 
extern void __bad_udelay(void); /* intentional errors */
extern void __bad_ndelay(void); /* intentional errors */
 
extern void __delay(unsigned long loops);
extern void __udelay(unsigned long usecs);
extern void __ndelay(unsigned long nsecs);
extern void __const_delay(unsigned long units);
 
#define udelay(n)                                                       \
        (__builtin_constant_p(n) ?                                      \
                ((n) > 20000 ? __bad_udelay()                           \
                             : __const_delay((n) * UDELAY_FACTOR))      \
                                 : __udelay(n))
 
#define ndelay(n)                                                       \
        (__builtin_constant_p(n) ?                                      \
                ((n) > 20000 ? __bad_ndelay()                           \
                             : __const_delay((n) * NDELAY_FACTOR))      \
                                 : __ndelay(n))
 
#endif
 
#endif /* defined(_ARM_DELAY_H) */
 

Line No.	Rev	Author	Line
1	1276	phoenix	`/*`
2			`* linux/include/asm-arm/delay.h`
3			`*`
4			`* Copyright (C) 1995-2003 Russell King`
5			`*`
6			`* This program is free software; you can redistribute it and/or modify`
7			`* it under the terms of the GNU General Public License version 2 as`
8			`* published by the Free Software Foundation.`
9			`*`
10			`* Delay routines, using a pre-computed "loops_per_second" value.`
11			`*/`
12			`#ifndef __ASM_ARM_DELAY_H`
13			`#define __ASM_ARM_DELAY_H`
14
15			`/*`
16			`* Division by multiplication and shifts.`
17			`*`
18			`* We want the number of loops to complete, where loops is:`
19			`* (us * (HZ * loops_per_jiffy)) / 10^6`
20			`* or`
21			`* (ns * (HZ * loops_per_jiffy)) / 10^9`
22			`*`
23			`* Since we don't want to do long division, we multiply both numerator`
24			`* and denominator by (2^28 / 10^6):`
25			`*`
26			`* (us * (2^28 / 10^6) * HZ * loops_per_jiffy) / 2^28`
27			`*`
28			`* => (us * (2^28 * HZ / 10^6) * loops_per_jiffy) / 2^28`
29			`*`
30			`* ~> (((us * (2^28 * HZ / 10^6)) / 2^11) * (loops_per_jiffy / 2^12)) / 2^5`
31			`* (for large loops_per_jiffy >> 2^12)`
32			`*`
33			`* Note: maximum loops_per_jiffy = 67108863 (bogomips = 1342.18)`
34			`* minimum loops_per_jiffy = 20000 (bogomips = 0.4)`
35			`*`
36			`* Note: we rely on HZ = 100.`
37			`*/`
38			`#define UDELAY_FACTOR 26843`
39			`#define NDELAY_FACTOR 27`
40
41			`#ifndef __ASSEMBLY__`
42
43			`extern void __bad_udelay(void); /* intentional errors */`
44			`extern void __bad_ndelay(void); /* intentional errors */`
45
46			`extern void __delay(unsigned long loops);`
47			`extern void __udelay(unsigned long usecs);`
48			`extern void __ndelay(unsigned long nsecs);`
49			`extern void __const_delay(unsigned long units);`
50
51			`#define udelay(n) \`
52			`(__builtin_constant_p(n) ? \`
53			`((n) > 20000 ? __bad_udelay() \`
54			`: __const_delay((n) * UDELAY_FACTOR)) \`
55			`: __udelay(n))`
56
57			`#define ndelay(n) \`
58			`(__builtin_constant_p(n) ? \`
59			`((n) > 20000 ? __bad_ndelay() \`
60			`: __const_delay((n) * NDELAY_FACTOR)) \`
61			`: __ndelay(n))`
62
63			`#endif`
64
65			`#endif /* defined(_ARM_DELAY_H) */`
66

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[/] [or1k/] [trunk/] [linux/] [linux-2.4/] [include/] [asm-arm/] [delay.h] - Blame information for rev 1276