drivers/acpi/acpica/utmath.c

   1 /*******************************************************************************
   2  *
   3  * Module Name: utmath - Integer math support routines
   4  *
   5  ******************************************************************************/
   6
   7 /*
   8  * Copyright (C) 2000 - 2010, Intel Corp.
   9  * All rights reserved.
  10  *
  11  * Redistribution and use in source and binary forms, with or without
  12  * modification, are permitted provided that the following conditions
  13  * are met:
  14  * 1. Redistributions of source code must retain the above copyright
  15  *    notice, this list of conditions, and the following disclaimer,
  16  *    without modification.
  17  * 2. Redistributions in binary form must reproduce at minimum a disclaimer
  18  *    substantially similar to the "NO WARRANTY" disclaimer below
  19  *    ("Disclaimer") and any redistribution must be conditioned upon
  20  *    including a substantially similar Disclaimer requirement for further
  21  *    binary redistribution.
  22  * 3. Neither the names of the above-listed copyright holders nor the names
  23  *    of any contributors may be used to endorse or promote products derived
  24  *    from this software without specific prior written permission.
  25  *
  26  * Alternatively, this software may be distributed under the terms of the
  27  * GNU General Public License ("GPL") version 2 as published by the Free
  28  * Software Foundation.
  29  *
  30  * NO WARRANTY
  31  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  32  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  33  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR
  34  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  35  * HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  36  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  37  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  38  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
  39  * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
  40  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  41  * POSSIBILITY OF SUCH DAMAGES.
  42  */
  43
  44 #include <acpi/acpi.h>
  45 #include "accommon.h"
  46
  47 #define _COMPONENT          ACPI_UTILITIES
  48 ACPI_MODULE_NAME("utmath")
  49
  50 /*
  51  * Support for double-precision integer divide.  This code is included here
  52  * in order to support kernel environments where the double-precision math
  53  * library is not available.
  54  */
  55 #ifndef ACPI_USE_NATIVE_DIVIDE
  56 /*******************************************************************************
  57  *
  58  * FUNCTION:    acpi_ut_short_divide
  59  *
  60  * PARAMETERS:  Dividend            - 64-bit dividend
  61  *              Divisor             - 32-bit divisor
  62  *              out_quotient        - Pointer to where the quotient is returned
  63  *              out_remainder       - Pointer to where the remainder is returned
  64  *
  65  * RETURN:      Status (Checks for divide-by-zero)
  66  *
  67  * DESCRIPTION: Perform a short (maximum 64 bits divided by 32 bits)
  68  *              divide and modulo.  The result is a 64-bit quotient and a
  69  *              32-bit remainder.
  70  *
  71  ******************************************************************************/
  72 acpi_status
  73 acpi_ut_short_divide(u64 dividend,
  74                      u32 divisor, u64 *out_quotient, u32 *out_remainder)
  75 {
  76         union uint64_overlay dividend_ovl;
  77         union uint64_overlay quotient;
  78         u32 remainder32;
  79
  80         ACPI_FUNCTION_TRACE(ut_short_divide);
  81
  82         /* Always check for a zero divisor */
  83
  84         if (divisor == 0) {
  85                 ACPI_ERROR((AE_INFO, "Divide by zero"));
  86                 return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO);
  87         }
  88
  89         dividend_ovl.full = dividend;
  90
  91         /*
  92          * The quotient is 64 bits, the remainder is always 32 bits,
  93          * and is generated by the second divide.
  94          */
  95         ACPI_DIV_64_BY_32(0, dividend_ovl.part.hi, divisor,
  96                           quotient.part.hi, remainder32);
  97         ACPI_DIV_64_BY_32(remainder32, dividend_ovl.part.lo, divisor,
  98                           quotient.part.lo, remainder32);
  99
 100         /* Return only what was requested */
 101
 102         if (out_quotient) {
 103                 *out_quotient = quotient.full;
 104         }
 105         if (out_remainder) {
 106                 *out_remainder = remainder32;
 107         }
 108
 109         return_ACPI_STATUS(AE_OK);
 110 }
 111
 112 /*******************************************************************************
 113  *
 114  * FUNCTION:    acpi_ut_divide
 115  *
 116  * PARAMETERS:  in_dividend         - Dividend
 117  *              in_divisor          - Divisor
 118  *              out_quotient        - Pointer to where the quotient is returned
 119  *              out_remainder       - Pointer to where the remainder is returned
 120  *
 121  * RETURN:      Status (Checks for divide-by-zero)
 122  *
 123  * DESCRIPTION: Perform a divide and modulo.
 124  *
 125  ******************************************************************************/
 126
 127 acpi_status
 128 acpi_ut_divide(u64 in_dividend,
 129                u64 in_divisor, u64 *out_quotient, u64 *out_remainder)
 130 {
 131         union uint64_overlay dividend;
 132         union uint64_overlay divisor;
 133         union uint64_overlay quotient;
 134         union uint64_overlay remainder;
 135         union uint64_overlay normalized_dividend;
 136         union uint64_overlay normalized_divisor;
 137         u32 partial1;
 138         union uint64_overlay partial2;
 139         union uint64_overlay partial3;
 140
 141         ACPI_FUNCTION_TRACE(ut_divide);
 142
 143         /* Always check for a zero divisor */
 144
 145         if (in_divisor == 0) {
 146                 ACPI_ERROR((AE_INFO, "Divide by zero"));
 147                 return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO);
 148         }
 149
 150         divisor.full = in_divisor;
 151         dividend.full = in_dividend;
 152         if (divisor.part.hi == 0) {
 153                 /*
 154                  * 1) Simplest case is where the divisor is 32 bits, we can
 155                  * just do two divides
 156                  */
 157                 remainder.part.hi = 0;
 158
 159                 /*
 160                  * The quotient is 64 bits, the remainder is always 32 bits,
 161                  * and is generated by the second divide.
 162                  */
 163                 ACPI_DIV_64_BY_32(0, dividend.part.hi, divisor.part.lo,
 164                                   quotient.part.hi, partial1);
 165                 ACPI_DIV_64_BY_32(partial1, dividend.part.lo, divisor.part.lo,
 166                                   quotient.part.lo, remainder.part.lo);
 167         }
 168
 169         else {
 170                 /*
 171                  * 2) The general case where the divisor is a full 64 bits
 172                  * is more difficult
 173                  */
 174                 quotient.part.hi = 0;
 175                 normalized_dividend = dividend;
 176                 normalized_divisor = divisor;
 177
 178                 /* Normalize the operands (shift until the divisor is < 32 bits) */
 179
 180                 do {
 181                         ACPI_SHIFT_RIGHT_64(normalized_divisor.part.hi,
 182                                             normalized_divisor.part.lo);
 183                         ACPI_SHIFT_RIGHT_64(normalized_dividend.part.hi,
 184                                             normalized_dividend.part.lo);
 185
 186                 } while (normalized_divisor.part.hi != 0);
 187
 188                 /* Partial divide */
 189
 190                 ACPI_DIV_64_BY_32(normalized_dividend.part.hi,
 191                                   normalized_dividend.part.lo,
 192                                   normalized_divisor.part.lo,
 193                                   quotient.part.lo, partial1);
 194
 195                 /*
 196                  * The quotient is always 32 bits, and simply requires adjustment.
 197                  * The 64-bit remainder must be generated.
 198                  */
 199                 partial1 = quotient.part.lo * divisor.part.hi;
 200                 partial2.full = (u64) quotient.part.lo * divisor.part.lo;
 201                 partial3.full = (u64) partial2.part.hi + partial1;
 202
 203                 remainder.part.hi = partial3.part.lo;
 204                 remainder.part.lo = partial2.part.lo;
 205
 206                 if (partial3.part.hi == 0) {
 207                         if (partial3.part.lo >= dividend.part.hi) {
 208                                 if (partial3.part.lo == dividend.part.hi) {
 209                                         if (partial2.part.lo > dividend.part.lo) {
 210                                                 quotient.part.lo--;
 211                                                 remainder.full -= divisor.full;
 212                                         }
 213                                 } else {
 214                                         quotient.part.lo--;
 215                                         remainder.full -= divisor.full;
 216                                 }
 217                         }
 218
 219                         remainder.full = remainder.full - dividend.full;
 220                         remainder.part.hi = (u32) - ((s32) remainder.part.hi);
 221                         remainder.part.lo = (u32) - ((s32) remainder.part.lo);
 222
 223                         if (remainder.part.lo) {
 224                                 remainder.part.hi--;
 225                         }
 226                 }
 227         }
 228
 229         /* Return only what was requested */
 230
 231         if (out_quotient) {
 232                 *out_quotient = quotient.full;
 233         }
 234         if (out_remainder) {
 235                 *out_remainder = remainder.full;
 236         }
 237
 238         return_ACPI_STATUS(AE_OK);
 239 }
 240
 241 #else
 242 /*******************************************************************************
 243  *
 244  * FUNCTION:    acpi_ut_short_divide, acpi_ut_divide
 245  *
 246  * PARAMETERS:  See function headers above
 247  *
 248  * DESCRIPTION: Native versions of the ut_divide functions. Use these if either
 249  *              1) The target is a 64-bit platform and therefore 64-bit
 250  *                 integer math is supported directly by the machine.
 251  *              2) The target is a 32-bit or 16-bit platform, and the
 252  *                 double-precision integer math library is available to
 253  *                 perform the divide.
 254  *
 255  ******************************************************************************/
 256 acpi_status
 257 acpi_ut_short_divide(u64 in_dividend,
 258                      u32 divisor, u64 *out_quotient, u32 *out_remainder)
 259 {
 260
 261         ACPI_FUNCTION_TRACE(ut_short_divide);
 262
 263         /* Always check for a zero divisor */
 264
 265         if (divisor == 0) {
 266                 ACPI_ERROR((AE_INFO, "Divide by zero"));
 267                 return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO);
 268         }
 269
 270         /* Return only what was requested */
 271
 272         if (out_quotient) {
 273                 *out_quotient = in_dividend / divisor;
 274         }
 275         if (out_remainder) {
 276                 *out_remainder = (u32) (in_dividend % divisor);
 277         }
 278
 279         return_ACPI_STATUS(AE_OK);
 280 }
 281
 282 acpi_status
 283 acpi_ut_divide(u64 in_dividend,
 284                u64 in_divisor, u64 *out_quotient, u64 *out_remainder)
 285 {
 286         ACPI_FUNCTION_TRACE(ut_divide);
 287
 288         /* Always check for a zero divisor */
 289
 290         if (in_divisor == 0) {
 291                 ACPI_ERROR((AE_INFO, "Divide by zero"));
 292                 return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO);
 293         }
 294
 295         /* Return only what was requested */
 296
 297         if (out_quotient) {
 298                 *out_quotient = in_dividend / in_divisor;
 299         }
 300         if (out_remainder) {
 301                 *out_remainder = in_dividend % in_divisor;
 302         }
 303
 304         return_ACPI_STATUS(AE_OK);
 305 }
 306
 307 #endif