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Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
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
Nicolas Pitredce1eb92015-11-02 13:02:46 -050016 * assembly versions such as arch/ppc/lib/div64.S and arch/sh/lib/div64.S
17 * or by defining a preprocessor macro in arch/include/asm/div64.h.
Linus Torvalds1da177e2005-04-16 15:20:36 -070018 */
19
Paul Gortmaker8bc3bcc2011-11-16 21:29:17 -050020#include <linux/export.h>
21#include <linux/kernel.h>
Roman Zippel2418f4f2008-05-01 04:34:25 -070022#include <linux/math64.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070023
24/* Not needed on 64bit architectures */
25#if BITS_PER_LONG == 32
26
Nicolas Pitredce1eb92015-11-02 13:02:46 -050027#ifndef __div64_32
David S. Millercb8c1812007-04-10 22:10:39 -070028uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base)
Linus Torvalds1da177e2005-04-16 15:20:36 -070029{
30 uint64_t rem = *n;
31 uint64_t b = base;
32 uint64_t res, d = 1;
33 uint32_t high = rem >> 32;
34
35 /* Reduce the thing a bit first */
36 res = 0;
37 if (high >= base) {
38 high /= base;
39 res = (uint64_t) high << 32;
40 rem -= (uint64_t) (high*base) << 32;
41 }
42
43 while ((int64_t)b > 0 && b < rem) {
44 b = b+b;
45 d = d+d;
46 }
47
48 do {
49 if (rem >= b) {
50 rem -= b;
51 res += d;
52 }
53 b >>= 1;
54 d >>= 1;
55 } while (d);
56
57 *n = res;
58 return rem;
59}
Linus Torvalds1da177e2005-04-16 15:20:36 -070060EXPORT_SYMBOL(__div64_32);
Nicolas Pitredce1eb92015-11-02 13:02:46 -050061#endif
Linus Torvalds1da177e2005-04-16 15:20:36 -070062
Roman Zippel2418f4f2008-05-01 04:34:25 -070063#ifndef div_s64_rem
64s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
65{
66 u64 quotient;
67
68 if (dividend < 0) {
69 quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder);
70 *remainder = -*remainder;
71 if (divisor > 0)
72 quotient = -quotient;
73 } else {
74 quotient = div_u64_rem(dividend, abs(divisor), (u32 *)remainder);
75 if (divisor < 0)
76 quotient = -quotient;
77 }
78 return quotient;
79}
80EXPORT_SYMBOL(div_s64_rem);
81#endif
82
Brian Behlendorf658716d2010-10-26 14:23:10 -070083/**
Mike Snitzereb18cba2013-08-20 15:05:17 -040084 * div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder
85 * @dividend: 64bit dividend
86 * @divisor: 64bit divisor
87 * @remainder: 64bit remainder
88 *
89 * This implementation is a comparable to algorithm used by div64_u64.
90 * But this operation, which includes math for calculating the remainder,
91 * is kept distinct to avoid slowing down the div64_u64 operation on 32bit
92 * systems.
93 */
94#ifndef div64_u64_rem
95u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder)
96{
97 u32 high = divisor >> 32;
98 u64 quot;
99
100 if (high == 0) {
101 u32 rem32;
102 quot = div_u64_rem(dividend, divisor, &rem32);
103 *remainder = rem32;
104 } else {
Stanislaw Gruszkaafac7da2019-03-07 16:28:18 -0800105 int n = fls(high);
Mike Snitzereb18cba2013-08-20 15:05:17 -0400106 quot = div_u64(dividend >> n, divisor >> n);
107
108 if (quot != 0)
109 quot--;
110
111 *remainder = dividend - quot * divisor;
112 if (*remainder >= divisor) {
113 quot++;
114 *remainder -= divisor;
115 }
116 }
117
118 return quot;
119}
120EXPORT_SYMBOL(div64_u64_rem);
121#endif
122
123/**
Stanislaw Gruszkaf3002132013-04-30 11:35:07 +0200124 * div64_u64 - unsigned 64bit divide with 64bit divisor
Brian Behlendorf658716d2010-10-26 14:23:10 -0700125 * @dividend: 64bit dividend
126 * @divisor: 64bit divisor
127 *
128 * This implementation is a modified version of the algorithm proposed
129 * by the book 'Hacker's Delight'. The original source and full proof
130 * can be found here and is available for use without restriction.
131 *
Heinrich Schuchardt28ca84e2015-02-26 20:19:03 +0100132 * 'http://www.hackersdelight.org/hdcodetxt/divDouble.c.txt'
Brian Behlendorf658716d2010-10-26 14:23:10 -0700133 */
Stanislaw Gruszkaf3002132013-04-30 11:35:07 +0200134#ifndef div64_u64
135u64 div64_u64(u64 dividend, u64 divisor)
Stephen Hemminger3927f2e2007-03-25 19:54:23 -0700136{
Brian Behlendorf658716d2010-10-26 14:23:10 -0700137 u32 high = divisor >> 32;
138 u64 quot;
Stephen Hemminger3927f2e2007-03-25 19:54:23 -0700139
Brian Behlendorf658716d2010-10-26 14:23:10 -0700140 if (high == 0) {
Stanislaw Gruszkaf3002132013-04-30 11:35:07 +0200141 quot = div_u64(dividend, divisor);
Brian Behlendorf658716d2010-10-26 14:23:10 -0700142 } else {
Stanislaw Gruszkaafac7da2019-03-07 16:28:18 -0800143 int n = fls(high);
Brian Behlendorf658716d2010-10-26 14:23:10 -0700144 quot = div_u64(dividend >> n, divisor >> n);
Stephen Hemminger3927f2e2007-03-25 19:54:23 -0700145
Brian Behlendorf658716d2010-10-26 14:23:10 -0700146 if (quot != 0)
147 quot--;
Stanislaw Gruszkaf3002132013-04-30 11:35:07 +0200148 if ((dividend - quot * divisor) >= divisor)
Brian Behlendorf658716d2010-10-26 14:23:10 -0700149 quot++;
150 }
Stephen Hemminger3927f2e2007-03-25 19:54:23 -0700151
Brian Behlendorf658716d2010-10-26 14:23:10 -0700152 return quot;
Stephen Hemminger3927f2e2007-03-25 19:54:23 -0700153}
Stanislaw Gruszkaf3002132013-04-30 11:35:07 +0200154EXPORT_SYMBOL(div64_u64);
Roman Zippel6f6d6a12008-05-01 04:34:28 -0700155#endif
Stephen Hemminger3927f2e2007-03-25 19:54:23 -0700156
Brian Behlendorf658716d2010-10-26 14:23:10 -0700157/**
158 * div64_s64 - signed 64bit divide with 64bit divisor
159 * @dividend: 64bit dividend
160 * @divisor: 64bit divisor
161 */
162#ifndef div64_s64
163s64 div64_s64(s64 dividend, s64 divisor)
164{
165 s64 quot, t;
166
Andrew Morton79211c82015-11-09 14:58:13 -0800167 quot = div64_u64(abs(dividend), abs(divisor));
Brian Behlendorf658716d2010-10-26 14:23:10 -0700168 t = (dividend ^ divisor) >> 63;
169
170 return (quot ^ t) - t;
171}
172EXPORT_SYMBOL(div64_s64);
173#endif
174
Linus Torvalds1da177e2005-04-16 15:20:36 -0700175#endif /* BITS_PER_LONG == 32 */
Jeremy Fitzhardingef595ec92008-06-12 10:47:56 +0200176
177/*
178 * Iterative div/mod for use when dividend is not expected to be much
179 * bigger than divisor.
180 */
181u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
182{
Jeremy Fitzhardinged5e181f2008-06-12 10:47:58 +0200183 return __iter_div_u64_rem(dividend, divisor, remainder);
Jeremy Fitzhardingef595ec92008-06-12 10:47:56 +0200184}
185EXPORT_SYMBOL(iter_div_u64_rem);