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Source at commit cdde9cf73945d547acd3e96f9508c79e84ad0bf1 created 12 years 9 months ago. By Maarten ter Huurne, MMC: JZ4740: Added support for CPU frequency changing | |
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1 | /* |
2 | * Copyright (C) 2003 Bernardo Innocenti <bernie@develer.com> |
3 | * |
4 | * Based on former do_div() implementation from asm-parisc/div64.h: |
5 | * Copyright (C) 1999 Hewlett-Packard Co |
6 | * Copyright (C) 1999 David Mosberger-Tang <davidm@hpl.hp.com> |
7 | * |
8 | * |
9 | * Generic C version of 64bit/32bit division and modulo, with |
10 | * 64bit result and 32bit remainder. |
11 | * |
12 | * The fast case for (n>>32 == 0) is handled inline by do_div(). |
13 | * |
14 | * Code generated for this function might be very inefficient |
15 | * for some CPUs. __div64_32() can be overridden by linking arch-specific |
16 | * assembly versions such as arch/ppc/lib/div64.S and arch/sh/lib/div64.S. |
17 | */ |
18 | |
19 | #include <linux/export.h> |
20 | #include <linux/kernel.h> |
21 | #include <linux/math64.h> |
22 | |
23 | /* Not needed on 64bit architectures */ |
24 | #if BITS_PER_LONG == 32 |
25 | |
26 | uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base) |
27 | { |
28 | uint64_t rem = *n; |
29 | uint64_t b = base; |
30 | uint64_t res, d = 1; |
31 | uint32_t high = rem >> 32; |
32 | |
33 | /* Reduce the thing a bit first */ |
34 | res = 0; |
35 | if (high >= base) { |
36 | high /= base; |
37 | res = (uint64_t) high << 32; |
38 | rem -= (uint64_t) (high*base) << 32; |
39 | } |
40 | |
41 | while ((int64_t)b > 0 && b < rem) { |
42 | b = b+b; |
43 | d = d+d; |
44 | } |
45 | |
46 | do { |
47 | if (rem >= b) { |
48 | rem -= b; |
49 | res += d; |
50 | } |
51 | b >>= 1; |
52 | d >>= 1; |
53 | } while (d); |
54 | |
55 | *n = res; |
56 | return rem; |
57 | } |
58 | |
59 | EXPORT_SYMBOL(__div64_32); |
60 | |
61 | #ifndef div_s64_rem |
62 | s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder) |
63 | { |
64 | u64 quotient; |
65 | |
66 | if (dividend < 0) { |
67 | quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder); |
68 | *remainder = -*remainder; |
69 | if (divisor > 0) |
70 | quotient = -quotient; |
71 | } else { |
72 | quotient = div_u64_rem(dividend, abs(divisor), (u32 *)remainder); |
73 | if (divisor < 0) |
74 | quotient = -quotient; |
75 | } |
76 | return quotient; |
77 | } |
78 | EXPORT_SYMBOL(div_s64_rem); |
79 | #endif |
80 | |
81 | /** |
82 | * div64_u64 - unsigned 64bit divide with 64bit divisor |
83 | * @dividend: 64bit dividend |
84 | * @divisor: 64bit divisor |
85 | * |
86 | * This implementation is a modified version of the algorithm proposed |
87 | * by the book 'Hacker's Delight'. The original source and full proof |
88 | * can be found here and is available for use without restriction. |
89 | * |
90 | * 'http://www.hackersdelight.org/HDcode/newCode/divDouble.c.txt' |
91 | */ |
92 | #ifndef div64_u64 |
93 | u64 div64_u64(u64 dividend, u64 divisor) |
94 | { |
95 | u32 high = divisor >> 32; |
96 | u64 quot; |
97 | |
98 | if (high == 0) { |
99 | quot = div_u64(dividend, divisor); |
100 | } else { |
101 | int n = 1 + fls(high); |
102 | quot = div_u64(dividend >> n, divisor >> n); |
103 | |
104 | if (quot != 0) |
105 | quot--; |
106 | if ((dividend - quot * divisor) >= divisor) |
107 | quot++; |
108 | } |
109 | |
110 | return quot; |
111 | } |
112 | EXPORT_SYMBOL(div64_u64); |
113 | #endif |
114 | |
115 | /** |
116 | * div64_s64 - signed 64bit divide with 64bit divisor |
117 | * @dividend: 64bit dividend |
118 | * @divisor: 64bit divisor |
119 | */ |
120 | #ifndef div64_s64 |
121 | s64 div64_s64(s64 dividend, s64 divisor) |
122 | { |
123 | s64 quot, t; |
124 | |
125 | quot = div64_u64(abs64(dividend), abs64(divisor)); |
126 | t = (dividend ^ divisor) >> 63; |
127 | |
128 | return (quot ^ t) - t; |
129 | } |
130 | EXPORT_SYMBOL(div64_s64); |
131 | #endif |
132 | |
133 | #endif /* BITS_PER_LONG == 32 */ |
134 | |
135 | /* |
136 | * Iterative div/mod for use when dividend is not expected to be much |
137 | * bigger than divisor. |
138 | */ |
139 | u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder) |
140 | { |
141 | return __iter_div_u64_rem(dividend, divisor, remainder); |
142 | } |
143 | EXPORT_SYMBOL(iter_div_u64_rem); |
144 |
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