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/compat.h> 21 #include <linux/kernel.h> 22 #include <linux/math64.h> 23 24 /* Not needed on 64bit architectures */ 25 #if BITS_PER_LONG == 32 26 27 #ifndef __div64_32 28 uint32_t __attribute__((weak)) __div64_32(uint64_t *n, uint32_t base) 29 { 30 uint64_t rem = *n; 31 uint64_t b = base; 32 uint64_t res, d = 1; 33 uint32_t high = rem >> 32; 34 35 /* Reduce the thing a bit first */ 36 res = 0; 37 if (high >= base) { 38 high /= base; 39 res = (uint64_t) high << 32; 40 rem -= (uint64_t) (high*base) << 32; 41 } 42 43 while ((int64_t)b > 0 && b < rem) { 44 b = b+b; 45 d = d+d; 46 } 47 48 do { 49 if (rem >= b) { 50 rem -= b; 51 res += d; 52 } 53 b >>= 1; 54 d >>= 1; 55 } while (d); 56 57 *n = res; 58 return rem; 59 } 60 EXPORT_SYMBOL(__div64_32); 61 #endif 62 63 #ifndef div_s64_rem 64 s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder) 65 { 66 u64 quotient; 67 68 if (dividend < 0) { 69 quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder); 70 *remainder = -*remainder; 71 if (divisor > 0) 72 quotient = -quotient; 73 } else { 74 quotient = div_u64_rem(dividend, abs(divisor), (u32 *)remainder); 75 if (divisor < 0) 76 quotient = -quotient; 77 } 78 return quotient; 79 } 80 EXPORT_SYMBOL(div_s64_rem); 81 #endif 82 83 /** 84 * div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder 85 * @dividend: 64bit dividend 86 * @divisor: 64bit divisor 87 * @remainder: 64bit remainder 88 * 89 * This implementation is a comparable to algorithm used by div64_u64. 90 * But this operation, which includes math for calculating the remainder, 91 * is kept distinct to avoid slowing down the div64_u64 operation on 32bit 92 * systems. 93 */ 94 #ifndef div64_u64_rem 95 u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder) 96 { 97 u32 high = divisor >> 32; 98 u64 quot; 99 100 if (high == 0) { 101 u32 rem32; 102 quot = div_u64_rem(dividend, divisor, &rem32); 103 *remainder = rem32; 104 } else { 105 int n = 1 + fls(high); 106 quot = div_u64(dividend >> n, divisor >> n); 107 108 if (quot != 0) 109 quot--; 110 111 *remainder = dividend - quot * divisor; 112 if (*remainder >= divisor) { 113 quot++; 114 *remainder -= divisor; 115 } 116 } 117 118 return quot; 119 } 120 EXPORT_SYMBOL(div64_u64_rem); 121 #endif 122 123 /** 124 * div64_u64 - unsigned 64bit divide with 64bit divisor 125 * @dividend: 64bit dividend 126 * @divisor: 64bit divisor 127 * 128 * This implementation is a modified version of the algorithm proposed 129 * by the book 'Hacker's Delight'. The original source and full proof 130 * can be found here and is available for use without restriction. 131 * 132 * 'http://www.hackersdelight.org/hdcodetxt/divDouble.c.txt' 133 */ 134 #ifndef div64_u64 135 u64 div64_u64(u64 dividend, u64 divisor) 136 { 137 u32 high = divisor >> 32; 138 u64 quot; 139 140 if (high == 0) { 141 quot = div_u64(dividend, divisor); 142 } else { 143 int n = 1 + fls(high); 144 quot = div_u64(dividend >> n, divisor >> n); 145 146 if (quot != 0) 147 quot--; 148 if ((dividend - quot * divisor) >= divisor) 149 quot++; 150 } 151 152 return quot; 153 } 154 EXPORT_SYMBOL(div64_u64); 155 #endif 156 157 /** 158 * div64_s64 - signed 64bit divide with 64bit divisor 159 * @dividend: 64bit dividend 160 * @divisor: 64bit divisor 161 */ 162 #ifndef div64_s64 163 s64 div64_s64(s64 dividend, s64 divisor) 164 { 165 s64 quot, t; 166 167 quot = div64_u64(abs(dividend), abs(divisor)); 168 t = (dividend ^ divisor) >> 63; 169 170 return (quot ^ t) - t; 171 } 172 EXPORT_SYMBOL(div64_s64); 173 #endif 174 175 #endif /* BITS_PER_LONG == 32 */ 176 177 /* 178 * Iterative div/mod for use when dividend is not expected to be much 179 * bigger than divisor. 180 */ 181 u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder) 182 { 183 return __iter_div_u64_rem(dividend, divisor, remainder); 184 } 185 EXPORT_SYMBOL(iter_div_u64_rem); 186