1/*
 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
 9#include <asm/memory.h>
10#include <asm/param.h>	/* HZ */
11
12/*
13 * Loop (or tick) based delay:
14 *
15 * loops = loops_per_jiffy * jiffies_per_sec * delay_us / us_per_sec
16 *
17 * where:
18 *
19 * jiffies_per_sec = HZ
20 * us_per_sec = 1000000
21 *
22 * Therefore the constant part is HZ / 1000000 which is a small
23 * fractional number. To make this usable with integer math, we
24 * scale up this constant by 2^31, perform the actual multiplication,
25 * and scale the result back down by 2^31 with a simple shift:
26 *
27 * loops = (loops_per_jiffy * delay_us * UDELAY_MULT) >> 31
28 *
29 * where:
30 *
31 * UDELAY_MULT = 2^31 * HZ / 1000000
32 *             = (2^31 / 1000000) * HZ
33 *             = 2147.483648 * HZ
34 *             = 2147 * HZ + 483648 * HZ / 1000000
35 *
36 * 31 is the biggest scale shift value that won't overflow 32 bits for
37 * delay_us * UDELAY_MULT assuming HZ <= 1000 and delay_us <= 2000.
38 */
39#define MAX_UDELAY_MS	2
40#define UDELAY_MULT	UL(2147 * HZ + 483648 * HZ / 1000000)
41#define UDELAY_SHIFT	31
42
43#ifndef __ASSEMBLY__
44
45struct delay_timer {
46	unsigned long (*read_current_timer)(void);
47	unsigned long freq;
48};
49
50extern struct arm_delay_ops {
51	void (*delay)(unsigned long);
52	void (*const_udelay)(unsigned long);
53	void (*udelay)(unsigned long);
54	unsigned long ticks_per_jiffy;
55} arm_delay_ops;
56
57#define __delay(n)		arm_delay_ops.delay(n)
58
59/*
60 * This function intentionally does not exist; if you see references to
61 * it, it means that you're calling udelay() with an out of range value.
62 *
63 * With currently imposed limits, this means that we support a max delay
64 * of 2000us. Further limits: HZ<=1000
65 */
66extern void __bad_udelay(void);
67
68/*
69 * division by multiplication: you don't have to worry about
70 * loss of precision.
71 *
72 * Use only for very small delays ( < 2 msec).  Should probably use a
73 * lookup table, really, as the multiplications take much too long with
74 * short delays.  This is a "reasonable" implementation, though (and the
75 * first constant multiplications gets optimized away if the delay is
76 * a constant)
77 */
78#define __udelay(n)		arm_delay_ops.udelay(n)
79#define __const_udelay(n)	arm_delay_ops.const_udelay(n)
 
 
80
81#define udelay(n)							\
82	(__builtin_constant_p(n) ?					\
83	  ((n) > (MAX_UDELAY_MS * 1000) ? __bad_udelay() :		\
84			__const_udelay((n) * UDELAY_MULT)) :		\
85	  __udelay(n))
86
87/* Loop-based definitions for assembly code. */
88extern void __loop_delay(unsigned long loops);
89extern void __loop_udelay(unsigned long usecs);
90extern void __loop_const_udelay(unsigned long);
91
92/* Delay-loop timer registration. */
93#define ARCH_HAS_READ_CURRENT_TIMER
94extern void register_current_timer_delay(const struct delay_timer *timer);
95
96#endif /* __ASSEMBLY__ */
97
98#endif /* defined(_ARM_DELAY_H) */
99

 1/*
 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
 
 9#include <asm/param.h>	/* HZ */
10
11extern 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
18 * of 2000us. Further limits: HZ<=1000 and bogomips<=3355
19 */
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
37#define udelay(n)							\
38	(__builtin_constant_p(n) ?					\
39	  ((n) > (MAX_UDELAY_MS * 1000) ? __bad_udelay() :		\
40			__const_udelay((n) * ((2199023U*HZ)>>11))) :	\
41	  __udelay(n))
 
 
 
 
 
 
 
 
 
 
 
42
43#endif /* defined(_ARM_DELAY_H) */
44