tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
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#include <linux/smp.h>
16#include <asm/compiler.h>
17
18static inline void __delay(unsigned long loops)
19{
20 if (sizeof(long) == 4)
21 __asm__ __volatile__ (
22 " .set noreorder \n"
23 " .align 3 \n"
24 "1: bnez %0, 1b \n"
25 " subu %0, 1 \n"
26 " .set reorder \n"
27 : "=r" (loops)
28 : "0" (loops));
29 else if (sizeof(long) == 8)
30 __asm__ __volatile__ (
31 " .set noreorder \n"
32 " .align 3 \n"
33 "1: bnez %0, 1b \n"
34 " dsubu %0, 1 \n"
35 " .set reorder \n"
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 rates of 128 is rounded wrongly by the catchall case
58 * for 64-bit. Excessive precission? Probably ...
59 */
60#if defined(CONFIG_64BIT) && (HZ == 128)
61 usecs *= 0x0008637bd05af6c7UL; /* 2**64 / (1000000 / HZ) */
62#elif defined(CONFIG_64BIT)
63 usecs *= (0x8000000000000000UL / (500000 / HZ));
64#else /* 32-bit junk follows here */
65 usecs *= (unsigned long) (((0x8000000000000000ULL / (500000 / HZ)) +
66 0x80000000ULL) >> 32);
67#endif
68
69 if (sizeof(long) == 4)
70 __asm__("multu\t%2, %3"
71 : "=h" (usecs), "=l" (lo)
72 : "r" (usecs), "r" (lpj)
73 : GCC_REG_ACCUM);
74 else if (sizeof(long) == 8)
75 __asm__("dmultu\t%2, %3"
76 : "=h" (usecs), "=l" (lo)
77 : "r" (usecs), "r" (lpj)
78 : GCC_REG_ACCUM);
79
80 __delay(usecs);
81}
82
83#define __udelay_val cpu_data[smp_processor_id()].udelay_val
84
85#define udelay(usecs) __udelay((usecs),__udelay_val)
86
87/* make sure "usecs *= ..." in udelay do not overflow. */
88#if HZ >= 1000
89#define MAX_UDELAY_MS 1
90#elif HZ <= 200
91#define MAX_UDELAY_MS 5
92#else
93#define MAX_UDELAY_MS (1000 / HZ)
94#endif
95
96#endif /* _ASM_DELAY_H */