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/module.h>
20 #include <linux/math64.h>
21
22 /* Not needed on 64bit architectures */
23 #if BITS_PER_LONG == 32
24
__div64_32(uint64_t * n,uint32_t base)25 uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base)
26 {
27 uint64_t rem = *n;
28 uint64_t b = base;
29 uint64_t res, d = 1;
30 uint32_t high = rem >> 32;
31
32 /* Reduce the thing a bit first */
33 res = 0;
34 if (high >= base) {
35 high /= base;
36 res = (uint64_t) high << 32;
37 rem -= (uint64_t) (high*base) << 32;
38 }
39
40 while ((int64_t)b > 0 && b < rem) {
41 b = b+b;
42 d = d+d;
43 }
44
45 do {
46 if (rem >= b) {
47 rem -= b;
48 res += d;
49 }
50 b >>= 1;
51 d >>= 1;
52 } while (d);
53
54 *n = res;
55 return rem;
56 }
57
58 EXPORT_SYMBOL(__div64_32);
59
60 #ifndef div_s64_rem
div_s64_rem(s64 dividend,s32 divisor,s32 * remainder)61 s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
62 {
63 u64 quotient;
64
65 if (dividend < 0) {
66 quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder);
67 *remainder = -*remainder;
68 if (divisor > 0)
69 quotient = -quotient;
70 } else {
71 quotient = div_u64_rem(dividend, abs(divisor), (u32 *)remainder);
72 if (divisor < 0)
73 quotient = -quotient;
74 }
75 return quotient;
76 }
77 EXPORT_SYMBOL(div_s64_rem);
78 #endif
79
80 /**
81 * div64_u64 - unsigned 64bit divide with 64bit divisor
82 * @dividend: 64bit dividend
83 * @divisor: 64bit divisor
84 *
85 * This implementation is a modified version of the algorithm proposed
86 * by the book 'Hacker's Delight'. The original source and full proof
87 * can be found here and is available for use without restriction.
88 *
89 * 'http://www.hackersdelight.org/HDcode/newCode/divDouble.c'
90 */
91 #ifndef div64_u64
div64_u64(u64 dividend,u64 divisor)92 u64 div64_u64(u64 dividend, u64 divisor)
93 {
94 u32 high = divisor >> 32;
95 u64 quot;
96
97 if (high == 0) {
98 quot = div_u64(dividend, divisor);
99 } else {
100 int n = 1 + fls(high);
101 quot = div_u64(dividend >> n, divisor >> n);
102
103 if (quot != 0)
104 quot--;
105 if ((dividend - quot * divisor) >= divisor)
106 quot++;
107 }
108
109 return quot;
110 }
111 EXPORT_SYMBOL(div64_u64);
112 #endif
113
114 /**
115 * div64_s64 - signed 64bit divide with 64bit divisor
116 * @dividend: 64bit dividend
117 * @divisor: 64bit divisor
118 */
119 #ifndef div64_s64
div64_s64(s64 dividend,s64 divisor)120 s64 div64_s64(s64 dividend, s64 divisor)
121 {
122 s64 quot, t;
123
124 quot = div64_u64(abs64(dividend), abs64(divisor));
125 t = (dividend ^ divisor) >> 63;
126
127 return (quot ^ t) - t;
128 }
129 EXPORT_SYMBOL(div64_s64);
130 #endif
131
132 #endif /* BITS_PER_LONG == 32 */
133
134 /*
135 * Iterative div/mod for use when dividend is not expected to be much
136 * bigger than divisor.
137 */
iter_div_u64_rem(u64 dividend,u32 divisor,u64 * remainder)138 u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
139 {
140 return __iter_div_u64_rem(dividend, divisor, remainder);
141 }
142 EXPORT_SYMBOL(iter_div_u64_rem);
143