Wolfgang Denk | 7b64fef | 2006-10-24 14:21:16 +0200 | [diff] [blame] | 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 |
Peng Fan | 0342e33 | 2017-04-10 13:39:48 +0800 | [diff] [blame] | 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. |
Wolfgang Denk | 7b64fef | 2006-10-24 14:21:16 +0200 | [diff] [blame] | 18 | */ |
| 19 | |
Peng Fan | 0342e33 | 2017-04-10 13:39:48 +0800 | [diff] [blame] | 20 | #include <linux/compat.h> |
| 21 | #include <linux/kernel.h> |
| 22 | #include <linux/math64.h> |
Wolfgang Denk | 7b64fef | 2006-10-24 14:21:16 +0200 | [diff] [blame] | 23 | |
Peng Fan | 0342e33 | 2017-04-10 13:39:48 +0800 | [diff] [blame] | 24 | /* Not needed on 64bit architectures */ |
| 25 | #if BITS_PER_LONG == 32 |
| 26 | |
| 27 | #ifndef __div64_32 |
Simon Glass | f611a46 | 2019-04-08 13:20:49 -0600 | [diff] [blame] | 28 | /* |
| 29 | * Don't instrument this function as it may be called from tracing code, since |
| 30 | * it needs to read the timer and this often requires calling do_div(), which |
| 31 | * calls this function. |
| 32 | */ |
| 33 | uint32_t __attribute__((weak, no_instrument_function)) __div64_32(u64 *n, |
| 34 | u32 base) |
Wolfgang Denk | 7b64fef | 2006-10-24 14:21:16 +0200 | [diff] [blame] | 35 | { |
Simon Glass | ca49b2c | 2019-04-08 13:20:48 -0600 | [diff] [blame] | 36 | u64 rem = *n; |
| 37 | u64 b = base; |
| 38 | u64 res, d = 1; |
| 39 | u32 high = rem >> 32; |
Wolfgang Denk | 7b64fef | 2006-10-24 14:21:16 +0200 | [diff] [blame] | 40 | |
| 41 | /* Reduce the thing a bit first */ |
| 42 | res = 0; |
| 43 | if (high >= base) { |
| 44 | high /= base; |
Simon Glass | ca49b2c | 2019-04-08 13:20:48 -0600 | [diff] [blame] | 45 | res = (u64)high << 32; |
| 46 | rem -= (u64)(high * base) << 32; |
Wolfgang Denk | 7b64fef | 2006-10-24 14:21:16 +0200 | [diff] [blame] | 47 | } |
| 48 | |
| 49 | while ((int64_t)b > 0 && b < rem) { |
| 50 | b = b+b; |
| 51 | d = d+d; |
| 52 | } |
| 53 | |
| 54 | do { |
| 55 | if (rem >= b) { |
| 56 | rem -= b; |
| 57 | res += d; |
| 58 | } |
| 59 | b >>= 1; |
| 60 | d >>= 1; |
| 61 | } while (d); |
| 62 | |
| 63 | *n = res; |
| 64 | return rem; |
| 65 | } |
Peng Fan | 0342e33 | 2017-04-10 13:39:48 +0800 | [diff] [blame] | 66 | EXPORT_SYMBOL(__div64_32); |
| 67 | #endif |
| 68 | |
| 69 | #ifndef div_s64_rem |
| 70 | s64 div_s64_rem(s64 dividend, s32 divisor, s32 *remainder) |
| 71 | { |
| 72 | u64 quotient; |
| 73 | |
| 74 | if (dividend < 0) { |
| 75 | quotient = div_u64_rem(-dividend, abs(divisor), (u32 *)remainder); |
| 76 | *remainder = -*remainder; |
| 77 | if (divisor > 0) |
| 78 | quotient = -quotient; |
| 79 | } else { |
| 80 | quotient = div_u64_rem(dividend, abs(divisor), (u32 *)remainder); |
| 81 | if (divisor < 0) |
| 82 | quotient = -quotient; |
| 83 | } |
| 84 | return quotient; |
| 85 | } |
| 86 | EXPORT_SYMBOL(div_s64_rem); |
| 87 | #endif |
| 88 | |
| 89 | /** |
| 90 | * div64_u64_rem - unsigned 64bit divide with 64bit divisor and remainder |
| 91 | * @dividend: 64bit dividend |
| 92 | * @divisor: 64bit divisor |
| 93 | * @remainder: 64bit remainder |
| 94 | * |
| 95 | * This implementation is a comparable to algorithm used by div64_u64. |
| 96 | * But this operation, which includes math for calculating the remainder, |
| 97 | * is kept distinct to avoid slowing down the div64_u64 operation on 32bit |
| 98 | * systems. |
| 99 | */ |
| 100 | #ifndef div64_u64_rem |
| 101 | u64 div64_u64_rem(u64 dividend, u64 divisor, u64 *remainder) |
| 102 | { |
| 103 | u32 high = divisor >> 32; |
| 104 | u64 quot; |
| 105 | |
| 106 | if (high == 0) { |
| 107 | u32 rem32; |
| 108 | quot = div_u64_rem(dividend, divisor, &rem32); |
| 109 | *remainder = rem32; |
| 110 | } else { |
| 111 | int n = 1 + fls(high); |
| 112 | quot = div_u64(dividend >> n, divisor >> n); |
| 113 | |
| 114 | if (quot != 0) |
| 115 | quot--; |
| 116 | |
| 117 | *remainder = dividend - quot * divisor; |
| 118 | if (*remainder >= divisor) { |
| 119 | quot++; |
| 120 | *remainder -= divisor; |
| 121 | } |
| 122 | } |
| 123 | |
| 124 | return quot; |
| 125 | } |
| 126 | EXPORT_SYMBOL(div64_u64_rem); |
| 127 | #endif |
| 128 | |
| 129 | /** |
| 130 | * div64_u64 - unsigned 64bit divide with 64bit divisor |
| 131 | * @dividend: 64bit dividend |
| 132 | * @divisor: 64bit divisor |
| 133 | * |
| 134 | * This implementation is a modified version of the algorithm proposed |
| 135 | * by the book 'Hacker's Delight'. The original source and full proof |
| 136 | * can be found here and is available for use without restriction. |
| 137 | * |
| 138 | * 'http://www.hackersdelight.org/hdcodetxt/divDouble.c.txt' |
| 139 | */ |
| 140 | #ifndef div64_u64 |
| 141 | u64 div64_u64(u64 dividend, u64 divisor) |
| 142 | { |
| 143 | u32 high = divisor >> 32; |
| 144 | u64 quot; |
| 145 | |
| 146 | if (high == 0) { |
| 147 | quot = div_u64(dividend, divisor); |
| 148 | } else { |
| 149 | int n = 1 + fls(high); |
| 150 | quot = div_u64(dividend >> n, divisor >> n); |
| 151 | |
| 152 | if (quot != 0) |
| 153 | quot--; |
| 154 | if ((dividend - quot * divisor) >= divisor) |
| 155 | quot++; |
| 156 | } |
| 157 | |
| 158 | return quot; |
| 159 | } |
| 160 | EXPORT_SYMBOL(div64_u64); |
| 161 | #endif |
| 162 | |
| 163 | /** |
| 164 | * div64_s64 - signed 64bit divide with 64bit divisor |
| 165 | * @dividend: 64bit dividend |
| 166 | * @divisor: 64bit divisor |
| 167 | */ |
| 168 | #ifndef div64_s64 |
| 169 | s64 div64_s64(s64 dividend, s64 divisor) |
| 170 | { |
| 171 | s64 quot, t; |
| 172 | |
| 173 | quot = div64_u64(abs(dividend), abs(divisor)); |
| 174 | t = (dividend ^ divisor) >> 63; |
| 175 | |
| 176 | return (quot ^ t) - t; |
| 177 | } |
| 178 | EXPORT_SYMBOL(div64_s64); |
| 179 | #endif |
| 180 | |
| 181 | #endif /* BITS_PER_LONG == 32 */ |
| 182 | |
| 183 | /* |
| 184 | * Iterative div/mod for use when dividend is not expected to be much |
| 185 | * bigger than divisor. |
| 186 | */ |
| 187 | u32 iter_div_u64_rem(u64 dividend, u32 divisor, u64 *remainder) |
| 188 | { |
| 189 | return __iter_div_u64_rem(dividend, divisor, remainder); |
| 190 | } |
| 191 | EXPORT_SYMBOL(iter_div_u64_rem); |