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
26uint32_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
59EXPORT_SYMBOL(__div64_32);
60
61#ifndef div_s64_rem
62s64 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}
78EXPORT_SYMBOL(div_s64_rem);
79#endif
80
81/**
82 * div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder
83 * @dividend:	64bit dividend
84 * @divisor:	64bit divisor
85 * @remainder:  64bit remainder
86 *
87 * This implementation is a comparable to algorithm used by div64_u64.
88 * But this operation, which includes math for calculating the remainder,
89 * is kept distinct to avoid slowing down the div64_u64 operation on 32bit
90 * systems.
91 */
92#ifndef div64_u64_rem
93u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder)
94{
95	u32 high = divisor >> 32;
96	u64 quot;
97
98	if (high == 0) {
99		u32 rem32;
100		quot = div_u64_rem(dividend, divisor, &rem32);
101		*remainder = rem32;
102	} else {
103		int n = 1 + fls(high);
104		quot = div_u64(dividend >> n, divisor >> n);
105
106		if (quot != 0)
107			quot--;
108
109		*remainder = dividend - quot * divisor;
110		if (*remainder >= divisor) {
111			quot++;
112			*remainder -= divisor;
113		}
114	}
115
116	return quot;
117}
118EXPORT_SYMBOL(div64_u64_rem);
119#endif
120
121/**
122 * div64_u64 - unsigned 64bit divide with 64bit divisor
123 * @dividend:	64bit dividend
124 * @divisor:	64bit divisor
125 *
126 * This implementation is a modified version of the algorithm proposed
127 * by the book 'Hacker's Delight'.  The original source and full proof
128 * can be found here and is available for use without restriction.
129 *
130 * 'http://www.hackersdelight.org/hdcodetxt/divDouble.c.txt'
131 */
132#ifndef div64_u64
133u64 div64_u64(u64 dividend, u64 divisor)
134{
135	u32 high = divisor >> 32;
136	u64 quot;
137
138	if (high == 0) {
139		quot = div_u64(dividend, divisor);
140	} else {
141		int n = 1 + fls(high);
142		quot = div_u64(dividend >> n, divisor >> n);
143
144		if (quot != 0)
145			quot--;
146		if ((dividend - quot * divisor) >= divisor)
147			quot++;
148	}
149
150	return quot;
151}
152EXPORT_SYMBOL(div64_u64);
153#endif
154
155/**
156 * div64_s64 - signed 64bit divide with 64bit divisor
157 * @dividend:	64bit dividend
158 * @divisor:	64bit divisor
159 */
160#ifndef div64_s64
161s64 div64_s64(s64 dividend, s64 divisor)
162{
163	s64 quot, t;
164
165	quot = div64_u64(abs64(dividend), abs64(divisor));
166	t = (dividend ^ divisor) >> 63;
167
168	return (quot ^ t) - t;
169}
170EXPORT_SYMBOL(div64_s64);
171#endif
172
173#endif /* BITS_PER_LONG == 32 */
174
175/*
176 * Iterative div/mod for use when dividend is not expected to be much
177 * bigger than divisor.
178 */
179u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
180{
181	return __iter_div_u64_rem(dividend, divisor, remainder);
182}
183EXPORT_SYMBOL(iter_div_u64_rem);
184