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1// SPDX-License-Identifier: GPL-2.0
2/*
3 * Copyright (C) 2003 Bernardo Innocenti <bernie@develer.com>
4 *
5 * Based on former do_div() implementation from asm-parisc/div64.h:
6 * Copyright (C) 1999 Hewlett-Packard Co
7 * Copyright (C) 1999 David Mosberger-Tang <davidm@hpl.hp.com>
8 *
9 *
10 * Generic C version of 64bit/32bit division and modulo, with
11 * 64bit result and 32bit remainder.
12 *
13 * The fast case for (n>>32 == 0) is handled inline by do_div().
14 *
15 * Code generated for this function might be very inefficient
16 * for some CPUs. __div64_32() can be overridden by linking arch-specific
17 * assembly versions such as arch/ppc/lib/div64.S and arch/sh/lib/div64.S
18 * or by defining a preprocessor macro in arch/include/asm/div64.h.
19 */
20
21#include <linux/export.h>
22#include <linux/kernel.h>
23#include <linux/math64.h>
24
25/* Not needed on 64bit architectures */
26#if BITS_PER_LONG == 32
27
28#ifndef __div64_32
29uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base)
30{
31 uint64_t rem = *n;
32 uint64_t b = base;
33 uint64_t res, d = 1;
34 uint32_t high = rem >> 32;
35
36 /* Reduce the thing a bit first */
37 res = 0;
38 if (high >= base) {
39 high /= base;
40 res = (uint64_t) high << 32;
41 rem -= (uint64_t) (high*base) << 32;
42 }
43
44 while ((int64_t)b > 0 && b < rem) {
45 b = b+b;
46 d = d+d;
47 }
48
49 do {
50 if (rem >= b) {
51 rem -= b;
52 res += d;
53 }
54 b >>= 1;
55 d >>= 1;
56 } while (d);
57
58 *n = res;
59 return rem;
60}
61EXPORT_SYMBOL(__div64_32);
62#endif
63
64#ifndef div_s64_rem
65s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
66{
67 u64 quotient;
68
69 if (dividend < 0) {
70 quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder);
71 *remainder = -*remainder;
72 if (divisor > 0)
73 quotient = -quotient;
74 } else {
75 quotient = div_u64_rem(dividend, abs(divisor), (u32 *)remainder);
76 if (divisor < 0)
77 quotient = -quotient;
78 }
79 return quotient;
80}
81EXPORT_SYMBOL(div_s64_rem);
82#endif
83
84/**
85 * div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder
86 * @dividend: 64bit dividend
87 * @divisor: 64bit divisor
88 * @remainder: 64bit remainder
89 *
90 * This implementation is a comparable to algorithm used by div64_u64.
91 * But this operation, which includes math for calculating the remainder,
92 * is kept distinct to avoid slowing down the div64_u64 operation on 32bit
93 * systems.
94 */
95#ifndef div64_u64_rem
96u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder)
97{
98 u32 high = divisor >> 32;
99 u64 quot;
100
101 if (high == 0) {
102 u32 rem32;
103 quot = div_u64_rem(dividend, divisor, &rem32);
104 *remainder = rem32;
105 } else {
106 int n = 1 + fls(high);
107 quot = div_u64(dividend >> n, divisor >> n);
108
109 if (quot != 0)
110 quot--;
111
112 *remainder = dividend - quot * divisor;
113 if (*remainder >= divisor) {
114 quot++;
115 *remainder -= divisor;
116 }
117 }
118
119 return quot;
120}
121EXPORT_SYMBOL(div64_u64_rem);
122#endif
123
124/**
125 * div64_u64 - unsigned 64bit divide with 64bit divisor
126 * @dividend: 64bit dividend
127 * @divisor: 64bit divisor
128 *
129 * This implementation is a modified version of the algorithm proposed
130 * by the book 'Hacker's Delight'. The original source and full proof
131 * can be found here and is available for use without restriction.
132 *
133 * 'http://www.hackersdelight.org/hdcodetxt/divDouble.c.txt'
134 */
135#ifndef div64_u64
136u64 div64_u64(u64 dividend, u64 divisor)
137{
138 u32 high = divisor >> 32;
139 u64 quot;
140
141 if (high == 0) {
142 quot = div_u64(dividend, divisor);
143 } else {
144 int n = 1 + fls(high);
145 quot = div_u64(dividend >> n, divisor >> n);
146
147 if (quot != 0)
148 quot--;
149 if ((dividend - quot * divisor) >= divisor)
150 quot++;
151 }
152
153 return quot;
154}
155EXPORT_SYMBOL(div64_u64);
156#endif
157
158/**
159 * div64_s64 - signed 64bit divide with 64bit divisor
160 * @dividend: 64bit dividend
161 * @divisor: 64bit divisor
162 */
163#ifndef div64_s64
164s64 div64_s64(s64 dividend, s64 divisor)
165{
166 s64 quot, t;
167
168 quot = div64_u64(abs(dividend), abs(divisor));
169 t = (dividend ^ divisor) >> 63;
170
171 return (quot ^ t) - t;
172}
173EXPORT_SYMBOL(div64_s64);
174#endif
175
176#endif /* BITS_PER_LONG == 32 */
177
178/*
179 * Iterative div/mod for use when dividend is not expected to be much
180 * bigger than divisor.
181 */
182u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
183{
184 return __iter_div_u64_rem(dividend, divisor, remainder);
185}
186EXPORT_SYMBOL(iter_div_u64_rem);