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 * or by defining a preprocessor macro in arch/include/asm/div64.h.
18 */
19
20#include <linux/bitops.h>
21#include <linux/compat.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/*
30 * Don't instrument this function as it may be called from tracing code, since
31 * it needs to read the timer and this often requires calling do_div(), which
32 * calls this function.
33 */
34uint32_t __attribute__((weak, no_instrument_function)) __div64_32(u64 *n,
35								  u32 base)
36{
37	u64 rem = *n;
38	u64 b = base;
39	u64 res, d = 1;
40	u32 high = rem >> 32;
41
42	/* Reduce the thing a bit first */
43	res = 0;
44	if (high >= base) {
45		high /= base;
46		res = (u64)high << 32;
47		rem -= (u64)(high * base) << 32;
48	}
49
50	while ((int64_t)b > 0 && b < rem) {
51		b = b+b;
52		d = d+d;
53	}
54
55	do {
56		if (rem >= b) {
57			rem -= b;
58			res += d;
59		}
60		b >>= 1;
61		d >>= 1;
62	} while (d);
63
64	*n = res;
65	return rem;
66}
67EXPORT_SYMBOL(__div64_32);
68#endif
69
70#ifndef div_s64_rem
71s64 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}
87EXPORT_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
102u64 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 = 1 + 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}
127EXPORT_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
142u64 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 = 1 + 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}
161EXPORT_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
170s64 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}
179EXPORT_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 */
188u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
189{
190	return __iter_div_u64_rem(dividend, divisor, remainder);
191}
192EXPORT_SYMBOL(iter_div_u64_rem);
193