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/* 64bit divisor, dividend and result. dynamic precision */ 81#ifndef div64_u64 82u64 div64_u64(u64 dividend, u64 divisor) 83{ 84 u32 high, d; 85 86 high = divisor >> 32; 87 if (high) { 88 unsigned int shift = fls(high); 89 90 d = divisor >> shift; 91 dividend >>= shift; 92 } else 93 d = divisor; 94 95 return div_u64(dividend, d); 96} 97EXPORT_SYMBOL(div64_u64); 98#endif 99 100#endif /* BITS_PER_LONG == 32 */ 101 102/* 103 * Iterative div/mod for use when dividend is not expected to be much 104 * bigger than divisor. 105 */ 106u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder) 107{ 108 return __iter_div_u64_rem(dividend, divisor, remainder); 109} 110EXPORT_SYMBOL(iter_div_u64_rem); 111