drivers/acpi/utilities/utmath.c

   1 /*******************************************************************************
   2  *
   3  * Module Name: utmath - Integer math support routines
   4  *
   5  ******************************************************************************/
   6
   7 /*
   8  * Copyright (C) 2000 - 2005, R. Byron Moore
   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
  45 #include <acpi/acpi.h>
  46
  47
  48 #define _COMPONENT          ACPI_UTILITIES
  49          ACPI_MODULE_NAME    ("utmath")
  50
  51 /*
  52  * Support for double-precision integer divide.  This code is included here
  53  * in order to support kernel environments where the double-precision math
  54  * library is not available.
  55  */
  56
  57 #ifndef ACPI_USE_NATIVE_DIVIDE
  58 /*******************************************************************************
  59  *
  60  * FUNCTION:    acpi_ut_short_divide
  61  *
  62  * PARAMETERS:  Dividend            - 64-bit dividend
  63  *              Divisor             - 32-bit divisor
  64  *              out_quotient        - Pointer to where the quotient is returned
  65  *              out_remainder       - Pointer to where the remainder is returned
  66  *
  67  * RETURN:      Status (Checks for divide-by-zero)
  68  *
  69  * DESCRIPTION: Perform a short (maximum 64 bits divided by 32 bits)
  70  *              divide and modulo.  The result is a 64-bit quotient and a
  71  *              32-bit remainder.
  72  *
  73  ******************************************************************************/
  74
  75 acpi_status
  76 acpi_ut_short_divide (
  77         acpi_integer                    dividend,
  78         u32                             divisor,
  79         acpi_integer                    *out_quotient,
  80         u32                             *out_remainder)
  81 {
  82         union uint64_overlay            dividend_ovl;
  83         union uint64_overlay            quotient;
  84         u32                             remainder32;
  85
  86
  87         ACPI_FUNCTION_TRACE ("ut_short_divide");
  88
  89
  90         /* Always check for a zero divisor */
  91
  92         if (divisor == 0) {
  93                 ACPI_REPORT_ERROR (("acpi_ut_short_divide: Divide by zero\n"));
  94                 return_ACPI_STATUS (AE_AML_DIVIDE_BY_ZERO);
  95         }
  96
  97         dividend_ovl.full = dividend;
  98
  99         /*
 100          * The quotient is 64 bits, the remainder is always 32 bits,
 101          * and is generated by the second divide.
 102          */
 103         ACPI_DIV_64_BY_32 (0, dividend_ovl.part.hi, divisor,
 104                           quotient.part.hi, remainder32);
 105         ACPI_DIV_64_BY_32 (remainder32, dividend_ovl.part.lo, divisor,
 106                           quotient.part.lo, remainder32);
 107
 108         /* Return only what was requested */
 109
 110         if (out_quotient) {
 111                 *out_quotient = quotient.full;
 112         }
 113         if (out_remainder) {
 114                 *out_remainder = remainder32;
 115         }
 116
 117         return_ACPI_STATUS (AE_OK);
 118 }
 119
 120
 121 /*******************************************************************************
 122  *
 123  * FUNCTION:    acpi_ut_divide
 124  *
 125  * PARAMETERS:  in_dividend         - Dividend
 126  *              in_divisor          - Divisor
 127  *              out_quotient        - Pointer to where the quotient is returned
 128  *              out_remainder       - Pointer to where the remainder is returned
 129  *
 130  * RETURN:      Status (Checks for divide-by-zero)
 131  *
 132  * DESCRIPTION: Perform a divide and modulo.
 133  *
 134  ******************************************************************************/
 135
 136 acpi_status
 137 acpi_ut_divide (
 138         acpi_integer                    in_dividend,
 139         acpi_integer                    in_divisor,
 140         acpi_integer                    *out_quotient,
 141         acpi_integer                    *out_remainder)
 142 {
 143         union uint64_overlay            dividend;
 144         union uint64_overlay            divisor;
 145         union uint64_overlay            quotient;
 146         union uint64_overlay            remainder;
 147         union uint64_overlay            normalized_dividend;
 148         union uint64_overlay            normalized_divisor;
 149         u32                             partial1;
 150         union uint64_overlay            partial2;
 151         union uint64_overlay            partial3;
 152
 153
 154         ACPI_FUNCTION_TRACE ("ut_divide");
 155
 156
 157         /* Always check for a zero divisor */
 158
 159         if (in_divisor == 0) {
 160                 ACPI_REPORT_ERROR (("acpi_ut_divide: Divide by zero\n"));
 161                 return_ACPI_STATUS (AE_AML_DIVIDE_BY_ZERO);
 162         }
 163
 164         divisor.full  = in_divisor;
 165         dividend.full = in_dividend;
 166         if (divisor.part.hi == 0) {
 167                 /*
 168                  * 1) Simplest case is where the divisor is 32 bits, we can
 169                  * just do two divides
 170                  */
 171                 remainder.part.hi = 0;
 172
 173                 /*
 174                  * The quotient is 64 bits, the remainder is always 32 bits,
 175                  * and is generated by the second divide.
 176                  */
 177                 ACPI_DIV_64_BY_32 (0, dividend.part.hi, divisor.part.lo,
 178                                   quotient.part.hi, partial1);
 179                 ACPI_DIV_64_BY_32 (partial1, dividend.part.lo, divisor.part.lo,
 180                                   quotient.part.lo, remainder.part.lo);
 181         }
 182
 183         else {
 184                 /*
 185                  * 2) The general case where the divisor is a full 64 bits
 186                  * is more difficult
 187                  */
 188                 quotient.part.hi   = 0;
 189                 normalized_dividend = dividend;
 190                 normalized_divisor = divisor;
 191
 192                 /* Normalize the operands (shift until the divisor is < 32 bits) */
 193
 194                 do {
 195                         ACPI_SHIFT_RIGHT_64 (normalized_divisor.part.hi,
 196                                          normalized_divisor.part.lo);
 197                         ACPI_SHIFT_RIGHT_64 (normalized_dividend.part.hi,
 198                                          normalized_dividend.part.lo);
 199
 200                 } while (normalized_divisor.part.hi != 0);
 201
 202                 /* Partial divide */
 203
 204                 ACPI_DIV_64_BY_32 (normalized_dividend.part.hi,
 205                                   normalized_dividend.part.lo,
 206                                   normalized_divisor.part.lo,
 207                                   quotient.part.lo, partial1);
 208
 209                 /*
 210                  * The quotient is always 32 bits, and simply requires adjustment.
 211                  * The 64-bit remainder must be generated.
 212                  */
 213                 partial1      = quotient.part.lo * divisor.part.hi;
 214                 partial2.full = (acpi_integer) quotient.part.lo * divisor.part.lo;
 215                 partial3.full = (acpi_integer) partial2.part.hi + partial1;
 216
 217                 remainder.part.hi = partial3.part.lo;
 218                 remainder.part.lo = partial2.part.lo;
 219
 220                 if (partial3.part.hi == 0) {
 221                         if (partial3.part.lo >= dividend.part.hi) {
 222                                 if (partial3.part.lo == dividend.part.hi) {
 223                                         if (partial2.part.lo > dividend.part.lo) {
 224                                                 quotient.part.lo--;
 225                                                 remainder.full -= divisor.full;
 226                                         }
 227                                 }
 228                                 else {
 229                                         quotient.part.lo--;
 230                                         remainder.full -= divisor.full;
 231                                 }
 232                         }
 233
 234                         remainder.full    = remainder.full - dividend.full;
 235                         remainder.part.hi = (u32) -((s32) remainder.part.hi);
 236                         remainder.part.lo = (u32) -((s32) remainder.part.lo);
 237
 238                         if (remainder.part.lo) {
 239                                 remainder.part.hi--;
 240                         }
 241                 }
 242         }
 243
 244         /* Return only what was requested */
 245
 246         if (out_quotient) {
 247                 *out_quotient = quotient.full;
 248         }
 249         if (out_remainder) {
 250                 *out_remainder = remainder.full;
 251         }
 252
 253         return_ACPI_STATUS (AE_OK);
 254 }
 255
 256 #else
 257
 258 /*******************************************************************************
 259  *
 260  * FUNCTION:    acpi_ut_short_divide, acpi_ut_divide
 261  *
 262  * DESCRIPTION: Native versions of the ut_divide functions. Use these if either
 263  *              1) The target is a 64-bit platform and therefore 64-bit
 264  *                 integer math is supported directly by the machine.
 265  *              2) The target is a 32-bit or 16-bit platform, and the
 266  *                 double-precision integer math library is available to
 267  *                 perform the divide.
 268  *
 269  ******************************************************************************/
 270
 271 acpi_status
 272 acpi_ut_short_divide (
 273         acpi_integer                    in_dividend,
 274         u32                             divisor,
 275         acpi_integer                    *out_quotient,
 276         u32                             *out_remainder)
 277 {
 278
 279         ACPI_FUNCTION_TRACE ("ut_short_divide");
 280
 281
 282         /* Always check for a zero divisor */
 283
 284         if (divisor == 0) {
 285                 ACPI_REPORT_ERROR (("acpi_ut_short_divide: Divide by zero\n"));
 286                 return_ACPI_STATUS (AE_AML_DIVIDE_BY_ZERO);
 287         }
 288
 289         /* Return only what was requested */
 290
 291         if (out_quotient) {
 292                 *out_quotient = in_dividend / divisor;
 293         }
 294         if (out_remainder) {
 295                 *out_remainder = (u32) in_dividend % divisor;
 296         }
 297
 298         return_ACPI_STATUS (AE_OK);
 299 }
 300
 301 acpi_status
 302 acpi_ut_divide (
 303         acpi_integer                    in_dividend,
 304         acpi_integer                    in_divisor,
 305         acpi_integer                    *out_quotient,
 306         acpi_integer                    *out_remainder)
 307 {
 308         ACPI_FUNCTION_TRACE ("ut_divide");
 309
 310
 311         /* Always check for a zero divisor */
 312
 313         if (in_divisor == 0) {
 314                 ACPI_REPORT_ERROR (("acpi_ut_divide: Divide by zero\n"));
 315                 return_ACPI_STATUS (AE_AML_DIVIDE_BY_ZERO);
 316         }
 317
 318
 319         /* Return only what was requested */
 320
 321         if (out_quotient) {
 322                 *out_quotient = in_dividend / in_divisor;
 323         }
 324         if (out_remainder) {
 325                 *out_remainder = in_dividend % in_divisor;
 326         }
 327
 328         return_ACPI_STATUS (AE_OK);
 329 }
 330
 331 #endif
 332
 333