drivers/acpi/utilities/utmath.c

   1 /*******************************************************************************
   2  *
   3  * Module Name: utmath - Integer math support routines
   4  *
   5  ******************************************************************************/
   6
   7 /*
   8  * Copyright (C) 2000 - 2004, 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:  in_dividend         - Pointer to the 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                    *in_dividend,
  78         u32                             divisor,
  79         acpi_integer                    *out_quotient,
  80         u32                             *out_remainder)
  81 {
  82         union uint64_overlay            dividend;
  83         union uint64_overlay            quotient;
  84         u32                             remainder32;
  85
  86
  87         ACPI_FUNCTION_TRACE ("ut_short_divide");
  88
  89         dividend.full = *in_dividend;
  90
  91         /* Always check for a zero divisor */
  92
  93         if (divisor == 0) {
  94                 ACPI_REPORT_ERROR (("acpi_ut_short_divide: Divide by zero\n"));
  95                 return_ACPI_STATUS (AE_AML_DIVIDE_BY_ZERO);
  96         }
  97
  98         /*
  99          * The quotient is 64 bits, the remainder is always 32 bits,
 100          * and is generated by the second divide.
 101          */
 102         ACPI_DIV_64_BY_32 (0, dividend.part.hi, divisor,
 103                           quotient.part.hi, remainder32);
 104         ACPI_DIV_64_BY_32 (remainder32, dividend.part.lo,  divisor,
 105                           quotient.part.lo, remainder32);
 106
 107         /* Return only what was requested */
 108
 109         if (out_quotient) {
 110                 *out_quotient = quotient.full;
 111         }
 112         if (out_remainder) {
 113                 *out_remainder = remainder32;
 114         }
 115
 116         return_ACPI_STATUS (AE_OK);
 117 }
 118
 119
 120 /*******************************************************************************
 121  *
 122  * FUNCTION:    acpi_ut_divide
 123  *
 124  * PARAMETERS:  in_dividend         - Pointer to the dividend
 125  *              in_divisor          - Pointer to the divisor
 126  *              out_quotient        - Pointer to where the quotient is returned
 127  *              out_remainder       - Pointer to where the remainder is returned
 128  *
 129  * RETURN:      Status (Checks for divide-by-zero)
 130  *
 131  * DESCRIPTION: Perform a divide and modulo.
 132  *
 133  ******************************************************************************/
 134
 135 acpi_status
 136 acpi_ut_divide (
 137         acpi_integer                    *in_dividend,
 138         acpi_integer                    *in_divisor,
 139         acpi_integer                    *out_quotient,
 140         acpi_integer                    *out_remainder)
 141 {
 142         union uint64_overlay            dividend;
 143         union uint64_overlay            divisor;
 144         union uint64_overlay            quotient;
 145         union uint64_overlay            remainder;
 146         union uint64_overlay            normalized_dividend;
 147         union uint64_overlay            normalized_divisor;
 148         u32                             partial1;
 149         union uint64_overlay            partial2;
 150         union uint64_overlay            partial3;
 151
 152
 153         ACPI_FUNCTION_TRACE ("ut_divide");
 154
 155
 156         /* Always check for a zero divisor */
 157
 158         if (*in_divisor == 0) {
 159                 ACPI_REPORT_ERROR (("acpi_ut_divide: Divide by zero\n"));
 160                 return_ACPI_STATUS (AE_AML_DIVIDE_BY_ZERO);
 161         }
 162
 163         divisor.full  = *in_divisor;
 164         dividend.full = *in_dividend;
 165         if (divisor.part.hi == 0) {
 166                 /*
 167                  * 1) Simplest case is where the divisor is 32 bits, we can
 168                  * just do two divides
 169                  */
 170                 remainder.part.hi = 0;
 171
 172                 /*
 173                  * The quotient is 64 bits, the remainder is always 32 bits,
 174                  * and is generated by the second divide.
 175                  */
 176                 ACPI_DIV_64_BY_32 (0, dividend.part.hi, divisor.part.lo,
 177                                   quotient.part.hi, partial1);
 178                 ACPI_DIV_64_BY_32 (partial1, dividend.part.lo, divisor.part.lo,
 179                                   quotient.part.lo, remainder.part.lo);
 180         }
 181
 182         else {
 183                 /*
 184                  * 2) The general case where the divisor is a full 64 bits
 185                  * is more difficult
 186                  */
 187                 quotient.part.hi   = 0;
 188                 normalized_dividend = dividend;
 189                 normalized_divisor = divisor;
 190
 191                 /* Normalize the operands (shift until the divisor is < 32 bits) */
 192
 193                 do {
 194                         ACPI_SHIFT_RIGHT_64 (normalized_divisor.part.hi,
 195                                          normalized_divisor.part.lo);
 196                         ACPI_SHIFT_RIGHT_64 (normalized_dividend.part.hi,
 197                                          normalized_dividend.part.lo);
 198
 199                 } while (normalized_divisor.part.hi != 0);
 200
 201                 /* Partial divide */
 202
 203                 ACPI_DIV_64_BY_32 (normalized_dividend.part.hi,
 204                                   normalized_dividend.part.lo,
 205                                   normalized_divisor.part.lo,
 206                                   quotient.part.lo, partial1);
 207
 208                 /*
 209                  * The quotient is always 32 bits, and simply requires adjustment.
 210                  * The 64-bit remainder must be generated.
 211                  */
 212                 partial1      = quotient.part.lo * divisor.part.hi;
 213                 partial2.full = (acpi_integer) quotient.part.lo * divisor.part.lo;
 214                 partial3.full = (acpi_integer) partial2.part.hi + partial1;
 215
 216                 remainder.part.hi = partial3.part.lo;
 217                 remainder.part.lo = partial2.part.lo;
 218
 219                 if (partial3.part.hi == 0) {
 220                         if (partial3.part.lo >= dividend.part.hi) {
 221                                 if (partial3.part.lo == dividend.part.hi) {
 222                                         if (partial2.part.lo > dividend.part.lo) {
 223                                                 quotient.part.lo--;
 224                                                 remainder.full -= divisor.full;
 225                                         }
 226                                 }
 227                                 else {
 228                                         quotient.part.lo--;
 229                                         remainder.full -= divisor.full;
 230                                 }
 231                         }
 232
 233                         remainder.full    = remainder.full - dividend.full;
 234                         remainder.part.hi = (u32) -((s32) remainder.part.hi);
 235                         remainder.part.lo = (u32) -((s32) remainder.part.lo);
 236
 237                         if (remainder.part.lo) {
 238                                 remainder.part.hi--;
 239                         }
 240                 }
 241         }
 242
 243         /* Return only what was requested */
 244
 245         if (out_quotient) {
 246                 *out_quotient = quotient.full;
 247         }
 248         if (out_remainder) {
 249                 *out_remainder = remainder.full;
 250         }
 251
 252         return_ACPI_STATUS (AE_OK);
 253 }
 254
 255 #else
 256
 257 /*******************************************************************************
 258  *
 259  * FUNCTION:    acpi_ut_short_divide, acpi_ut_divide
 260  *
 261  * DESCRIPTION: Native versions of the ut_divide functions. Use these if either
 262  *              1) The target is a 64-bit platform and therefore 64-bit
 263  *                 integer math is supported directly by the machine.
 264  *              2) The target is a 32-bit or 16-bit platform, and the
 265  *                 double-precision integer math library is available to
 266  *                 perform the divide.
 267  *
 268  ******************************************************************************/
 269
 270 acpi_status
 271 acpi_ut_short_divide (
 272         acpi_integer                    *in_dividend,
 273         u32                             divisor,
 274         acpi_integer                    *out_quotient,
 275         u32                             *out_remainder)
 276 {
 277
 278         ACPI_FUNCTION_TRACE ("ut_short_divide");
 279
 280
 281         /* Always check for a zero divisor */
 282
 283         if (divisor == 0) {
 284                 ACPI_REPORT_ERROR (("acpi_ut_short_divide: Divide by zero\n"));
 285                 return_ACPI_STATUS (AE_AML_DIVIDE_BY_ZERO);
 286         }
 287
 288         /* Return only what was requested */
 289
 290         if (out_quotient) {
 291                 *out_quotient = *in_dividend / divisor;
 292         }
 293         if (out_remainder) {
 294                 *out_remainder = (u32) *in_dividend % divisor;
 295         }
 296
 297         return_ACPI_STATUS (AE_OK);
 298 }
 299
 300 acpi_status
 301 acpi_ut_divide (
 302         acpi_integer                    *in_dividend,
 303         acpi_integer                    *in_divisor,
 304         acpi_integer                    *out_quotient,
 305         acpi_integer                    *out_remainder)
 306 {
 307         ACPI_FUNCTION_TRACE ("ut_divide");
 308
 309
 310         /* Always check for a zero divisor */
 311
 312         if (*in_divisor == 0) {
 313                 ACPI_REPORT_ERROR (("acpi_ut_divide: Divide by zero\n"));
 314                 return_ACPI_STATUS (AE_AML_DIVIDE_BY_ZERO);
 315         }
 316
 317
 318         /* Return only what was requested */
 319
 320         if (out_quotient) {
 321                 *out_quotient = *in_dividend / *in_divisor;
 322         }
 323         if (out_remainder) {
 324                 *out_remainder = *in_dividend % *in_divisor;
 325         }
 326
 327         return_ACPI_STATUS (AE_OK);
 328 }
 329
 330 #endif
 331
 332