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/module.h>
 20#include <linux/math64.h>
 21
 22/* Not needed on 64bit architectures */
 23#if BITS_PER_LONG == 32
 24
 25uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base)
 26{
 27	uint64_t rem = *n;
 28	uint64_t b = base;
 29	uint64_t res, d = 1;
 30	uint32_t high = rem >> 32;
 31
 32	/* Reduce the thing a bit first */
 33	res = 0;
 34	if (high >= base) {
 35		high /= base;
 36		res = (uint64_t) high << 32;
 37		rem -= (uint64_t) (high*base) << 32;
 38	}
 39
 40	while ((int64_t)b > 0 && b < rem) {
 41		b = b+b;
 42		d = d+d;
 43	}
 44
 45	do {
 46		if (rem >= b) {
 47			rem -= b;
 48			res += d;
 49		}
 50		b >>= 1;
 51		d >>= 1;
 52	} while (d);
 53
 54	*n = res;
 55	return rem;
 56}
 57
 58EXPORT_SYMBOL(__div64_32);
 59
 60#ifndef div_s64_rem
 61s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder)
 62{
 63	u64 quotient;
 64
 65	if (dividend < 0) {
 66		quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder);
 67		*remainder = -*remainder;
 68		if (divisor > 0)
 69			quotient = -quotient;
 70	} else {
 71		quotient = div_u64_rem(dividend, abs(divisor), (u32 *)remainder);
 72		if (divisor < 0)
 73			quotient = -quotient;
 74	}
 75	return quotient;
 76}
 77EXPORT_SYMBOL(div_s64_rem);
 78#endif
 79
 80/**
 81 * div64_u64 - unsigned 64bit divide with 64bit divisor
 82 * @dividend:	64bit dividend
 83 * @divisor:	64bit divisor
 84 *
 85 * This implementation is a modified version of the algorithm proposed
 86 * by the book 'Hacker's Delight'.  The original source and full proof
 87 * can be found here and is available for use without restriction.
 88 *
 89 * 'http://www.hackersdelight.org/HDcode/newCode/divDouble.c'
 90 */
 91#ifndef div64_u64
 92u64 div64_u64(u64 dividend, u64 divisor)
 93{
 94	u32 high = divisor >> 32;
 95	u64 quot;
 96
 97	if (high == 0) {
 98		quot = div_u64(dividend, divisor);
 99	} else {
100		int n = 1 + fls(high);
101		quot = div_u64(dividend >> n, divisor >> n);
102
103		if (quot != 0)
104			quot--;
105		if ((dividend - quot * divisor) >= divisor)
106			quot++;
107	}
108
109	return quot;
110}
111EXPORT_SYMBOL(div64_u64);
112#endif
113
114/**
115 * div64_s64 - signed 64bit divide with 64bit divisor
116 * @dividend:	64bit dividend
117 * @divisor:	64bit divisor
118 */
119#ifndef div64_s64
120s64 div64_s64(s64 dividend, s64 divisor)
121{
122	s64 quot, t;
123
124	quot = div64_u64(abs64(dividend), abs64(divisor));
125	t = (dividend ^ divisor) >> 63;
126
127	return (quot ^ t) - t;
128}
129EXPORT_SYMBOL(div64_s64);
130#endif
131
132#endif /* BITS_PER_LONG == 32 */
133
134/*
135 * Iterative div/mod for use when dividend is not expected to be much
136 * bigger than divisor.
137 */
138u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder)
139{
140	return __iter_div_u64_rem(dividend, divisor, remainder);
141}
142EXPORT_SYMBOL(iter_div_u64_rem);