Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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linux
1/*
2 * This file is subject to the terms and conditions of the GNU General Public
3 * License. See the file "COPYING" in the main directory of this archive
4 * for more details.
5 *
6 * Copyright (C) 1994 by Waldorf Electronics
7 * Copyright (C) 1995 - 2000, 01, 03 by Ralf Baechle
8 * Copyright (C) 1999, 2000 Silicon Graphics, Inc.
9 */
10#ifndef _ASM_DELAY_H
11#define _ASM_DELAY_H
12
13#include <linux/config.h>
14#include <linux/param.h>
15
16#include <asm/compiler.h>
17
18extern unsigned long loops_per_jiffy;
19
20static inline void __delay(unsigned long loops)
21{
22 if (sizeof(long) == 4)
23 __asm__ __volatile__ (
24 ".set\tnoreorder\n"
25 "1:\tbnez\t%0,1b\n\t"
26 "subu\t%0,1\n\t"
27 ".set\treorder"
28 : "=r" (loops)
29 : "0" (loops));
30 else if (sizeof(long) == 8)
31 __asm__ __volatile__ (
32 ".set\tnoreorder\n"
33 "1:\tbnez\t%0,1b\n\t"
34 "dsubu\t%0,1\n\t"
35 ".set\treorder"
36 :"=r" (loops)
37 :"0" (loops));
38}
39
40
41/*
42 * Division by multiplication: you don't have to worry about
43 * loss of precision.
44 *
45 * Use only for very small delays ( < 1 msec). Should probably use a
46 * lookup table, really, as the multiplications take much too long with
47 * short delays. This is a "reasonable" implementation, though (and the
48 * first constant multiplications gets optimized away if the delay is
49 * a constant)
50 */
51
52static inline void __udelay(unsigned long usecs, unsigned long lpj)
53{
54 unsigned long lo;
55
56 /*
57 * The common rates of 1000 and 128 are rounded wrongly by the
58 * catchall case for 64-bit. Excessive precission? Probably ...
59 */
60#if defined(CONFIG_MIPS64) && (HZ == 128)
61 usecs *= 0x0008637bd05af6c7UL; /* 2**64 / (1000000 / HZ) */
62#elif defined(CONFIG_MIPS64) && (HZ == 1000)
63 usecs *= 0x004189374BC6A7f0UL; /* 2**64 / (1000000 / HZ) */
64#elif defined(CONFIG_MIPS64)
65 usecs *= (0x8000000000000000UL / (500000 / HZ));
66#else /* 32-bit junk follows here */
67 usecs *= (unsigned long) (((0x8000000000000000ULL / (500000 / HZ)) +
68 0x80000000ULL) >> 32);
69#endif
70
71 if (sizeof(long) == 4)
72 __asm__("multu\t%2, %3"
73 : "=h" (usecs), "=l" (lo)
74 : "r" (usecs), "r" (lpj)
75 : GCC_REG_ACCUM);
76 else if (sizeof(long) == 8)
77 __asm__("dmultu\t%2, %3"
78 : "=h" (usecs), "=l" (lo)
79 : "r" (usecs), "r" (lpj)
80 : GCC_REG_ACCUM);
81
82 __delay(usecs);
83}
84
85#ifdef CONFIG_SMP
86#define __udelay_val cpu_data[smp_processor_id()].udelay_val
87#else
88#define __udelay_val loops_per_jiffy
89#endif
90
91#define udelay(usecs) __udelay((usecs),__udelay_val)
92
93#endif /* _ASM_DELAY_H */