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
29 uint32_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 }
61 EXPORT_SYMBOL(__div64_32);
62 #endif
63
64 /**
65 * div_s64_rem - signed 64bit divide with 64bit divisor and remainder
66 * @dividend: 64bit dividend
67 * @divisor: 64bit divisor
68 * @remainder: 64bit remainder
69 */
70 #ifndef div_s64_rem
71 s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
72 {
73 u64 quotient;
74
75 if (dividend < 0) {
76 quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder);
77 *remainder = -*remainder;
78 if (divisor > 0)
79 quotient = -quotient;
80 } else {
81 quotient = div_u64_rem(dividend, abs(divisor), (u32 *)remainder);
82 if (divisor < 0)
83 quotient = -quotient;
84 }
85 return quotient;
86 }
87 EXPORT_SYMBOL(div_s64_rem);
88 #endif
89
90 /**
91 * div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder
92 * @dividend: 64bit dividend
93 * @divisor: 64bit divisor
94 * @remainder: 64bit remainder
95 *
96 * This implementation is a comparable to algorithm used by div64_u64.
97 * But this operation, which includes math for calculating the remainder,
98 * is kept distinct to avoid slowing down the div64_u64 operation on 32bit
99 * systems.
100 */
101 #ifndef div64_u64_rem
102 u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder)
103 {
104 u32 high = divisor >> 32;
105 u64 quot;
106
107 if (high == 0) {
108 u32 rem32;
109 quot = div_u64_rem(dividend, divisor, &rem32);
110 *remainder = rem32;
111 } else {
112 int n = fls(high);
113 quot = div_u64(dividend >> n, divisor >> n);
114
115 if (quot != 0)
116 quot--;
117
118 *remainder = dividend - quot * divisor;
119 if (*remainder >= divisor) {
120 quot++;
121 *remainder -= divisor;
122 }
123 }
124
125 return quot;
126 }
127 EXPORT_SYMBOL(div64_u64_rem);
128 #endif
129
130 /**
131 * div64_u64 - unsigned 64bit divide with 64bit divisor
132 * @dividend: 64bit dividend
133 * @divisor: 64bit divisor
134 *
135 * This implementation is a modified version of the algorithm proposed
136 * by the book 'Hacker's Delight'. The original source and full proof
137 * can be found here and is available for use without restriction.
138 *
139 * 'http://www.hackersdelight.org/hdcodetxt/divDouble.c.txt'
140 */
141 #ifndef div64_u64
142 u64 div64_u64(u64 dividend, u64 divisor)
143 {
144 u32 high = divisor >> 32;
145 u64 quot;
146
147 if (high == 0) {
148 quot = div_u64(dividend, divisor);
149 } else {
150 int n = fls(high);
151 quot = div_u64(dividend >> n, divisor >> n);
152
153 if (quot != 0)
154 quot--;
155 if ((dividend - quot * divisor) >= divisor)
156 quot++;
157 }
158
159 return quot;
160 }
161 EXPORT_SYMBOL(div64_u64);
162 #endif
163
164 /**
165 * div64_s64 - signed 64bit divide with 64bit divisor
166 * @dividend: 64bit dividend
167 * @divisor: 64bit divisor
168 */
169 #ifndef div64_s64
170 s64 div64_s64(s64 dividend, s64 divisor)
171 {
172 s64 quot, t;
173
174 quot = div64_u64(abs(dividend), abs(divisor));
175 t = (dividend ^ divisor) >> 63;
176
177 return (quot ^ t) - t;
178 }
179 EXPORT_SYMBOL(div64_s64);
180 #endif
181
182 #endif /* BITS_PER_LONG == 32 */
183
184 /*
185 * Iterative div/mod for use when dividend is not expected to be much
186 * bigger than divisor.
187 */
188 u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
189 {
190 return __iter_div_u64_rem(dividend, divisor, remainder);
191 }
192 EXPORT_SYMBOL(iter_div_u64_rem);