git.oblomov.eu Git - linux-2.6/blob - drivers/acpi/acpica/utmath.c

   1 /*******************************************************************************
   2  *
   3  * Module Name: utmath - Integer math support routines
   4  *
   5  ******************************************************************************/
   6
   7 /*
   8  * Copyright (C) 2000 - 2008, 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(acpi_integer dividend,
  74                      u32 divisor,
  75                      acpi_integer * out_quotient, u32 * out_remainder)
  76 {
  77         union uint64_overlay dividend_ovl;
  78         union uint64_overlay quotient;
  79         u32 remainder32;
  80
  81         ACPI_FUNCTION_TRACE(ut_short_divide);
  82
  83         /* Always check for a zero divisor */
  84
  85         if (divisor == 0) {
  86                 ACPI_ERROR((AE_INFO, "Divide by zero"));
  87                 return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO);
  88         }
  89
  90         dividend_ovl.full = dividend;
  91
  92         /*
  93          * The quotient is 64 bits, the remainder is always 32 bits,
  94          * and is generated by the second divide.
  95          */
  96         ACPI_DIV_64_BY_32(0, dividend_ovl.part.hi, divisor,
  97                           quotient.part.hi, remainder32);
  98         ACPI_DIV_64_BY_32(remainder32, dividend_ovl.part.lo, divisor,
  99                           quotient.part.lo, remainder32);
 100
 101         /* Return only what was requested */
 102
 103         if (out_quotient) {
 104                 *out_quotient = quotient.full;
 105         }
 106         if (out_remainder) {
 107                 *out_remainder = remainder32;
 108         }
 109
 110         return_ACPI_STATUS(AE_OK);
 111 }
 112
 113 /*******************************************************************************
 114  *
 115  * FUNCTION:    acpi_ut_divide
 116  *
 117  * PARAMETERS:  in_dividend         - Dividend
 118  *              in_divisor          - Divisor
 119  *              out_quotient        - Pointer to where the quotient is returned
 120  *              out_remainder       - Pointer to where the remainder is returned
 121  *
 122  * RETURN:      Status (Checks for divide-by-zero)
 123  *
 124  * DESCRIPTION: Perform a divide and modulo.
 125  *
 126  ******************************************************************************/
 127
 128 acpi_status
 129 acpi_ut_divide(acpi_integer in_dividend,
 130                acpi_integer in_divisor,
 131                acpi_integer * out_quotient, acpi_integer * out_remainder)
 132 {
 133         union uint64_overlay dividend;
 134         union uint64_overlay divisor;
 135         union uint64_overlay quotient;
 136         union uint64_overlay remainder;
 137         union uint64_overlay normalized_dividend;
 138         union uint64_overlay normalized_divisor;
 139         u32 partial1;
 140         union uint64_overlay partial2;
 141         union uint64_overlay partial3;
 142
 143         ACPI_FUNCTION_TRACE(ut_divide);
 144
 145         /* Always check for a zero divisor */
 146
 147         if (in_divisor == 0) {
 148                 ACPI_ERROR((AE_INFO, "Divide by zero"));
 149                 return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO);
 150         }
 151
 152         divisor.full = in_divisor;
 153         dividend.full = in_dividend;
 154         if (divisor.part.hi == 0) {
 155                 /*
 156                  * 1) Simplest case is where the divisor is 32 bits, we can
 157                  * just do two divides
 158                  */
 159                 remainder.part.hi = 0;
 160
 161                 /*
 162                  * The quotient is 64 bits, the remainder is always 32 bits,
 163                  * and is generated by the second divide.
 164                  */
 165                 ACPI_DIV_64_BY_32(0, dividend.part.hi, divisor.part.lo,
 166                                   quotient.part.hi, partial1);
 167                 ACPI_DIV_64_BY_32(partial1, dividend.part.lo, divisor.part.lo,
 168                                   quotient.part.lo, remainder.part.lo);
 169         }
 170
 171         else {
 172                 /*
 173                  * 2) The general case where the divisor is a full 64 bits
 174                  * is more difficult
 175                  */
 176                 quotient.part.hi = 0;
 177                 normalized_dividend = dividend;
 178                 normalized_divisor = divisor;
 179
 180                 /* Normalize the operands (shift until the divisor is < 32 bits) */
 181
 182                 do {
 183                         ACPI_SHIFT_RIGHT_64(normalized_divisor.part.hi,
 184                                             normalized_divisor.part.lo);
 185                         ACPI_SHIFT_RIGHT_64(normalized_dividend.part.hi,
 186                                             normalized_dividend.part.lo);
 187
 188                 } while (normalized_divisor.part.hi != 0);
 189
 190                 /* Partial divide */
 191
 192                 ACPI_DIV_64_BY_32(normalized_dividend.part.hi,
 193                                   normalized_dividend.part.lo,
 194                                   normalized_divisor.part.lo,
 195                                   quotient.part.lo, partial1);
 196
 197                 /*
 198                  * The quotient is always 32 bits, and simply requires adjustment.
 199                  * The 64-bit remainder must be generated.
 200                  */
 201                 partial1 = quotient.part.lo * divisor.part.hi;
 202                 partial2.full =
 203                     (acpi_integer) quotient.part.lo * divisor.part.lo;
 204                 partial3.full = (acpi_integer) partial2.part.hi + partial1;
 205
 206                 remainder.part.hi = partial3.part.lo;
 207                 remainder.part.lo = partial2.part.lo;
 208
 209                 if (partial3.part.hi == 0) {
 210                         if (partial3.part.lo >= dividend.part.hi) {
 211                                 if (partial3.part.lo == dividend.part.hi) {
 212                                         if (partial2.part.lo > dividend.part.lo) {
 213                                                 quotient.part.lo--;
 214                                                 remainder.full -= divisor.full;
 215                                         }
 216                                 } else {
 217                                         quotient.part.lo--;
 218                                         remainder.full -= divisor.full;
 219                                 }
 220                         }
 221
 222                         remainder.full = remainder.full - dividend.full;
 223                         remainder.part.hi = (u32) - ((s32) remainder.part.hi);
 224                         remainder.part.lo = (u32) - ((s32) remainder.part.lo);
 225
 226                         if (remainder.part.lo) {
 227                                 remainder.part.hi--;
 228                         }
 229                 }
 230         }
 231
 232         /* Return only what was requested */
 233
 234         if (out_quotient) {
 235                 *out_quotient = quotient.full;
 236         }
 237         if (out_remainder) {
 238                 *out_remainder = remainder.full;
 239         }
 240
 241         return_ACPI_STATUS(AE_OK);
 242 }
 243
 244 #else
 245 /*******************************************************************************
 246  *
 247  * FUNCTION:    acpi_ut_short_divide, acpi_ut_divide
 248  *
 249  * PARAMETERS:  See function headers above
 250  *
 251  * DESCRIPTION: Native versions of the ut_divide functions. Use these if either
 252  *              1) The target is a 64-bit platform and therefore 64-bit
 253  *                 integer math is supported directly by the machine.
 254  *              2) The target is a 32-bit or 16-bit platform, and the
 255  *                 double-precision integer math library is available to
 256  *                 perform the divide.
 257  *
 258  ******************************************************************************/
 259 acpi_status
 260 acpi_ut_short_divide(acpi_integer in_dividend,
 261                      u32 divisor,
 262                      acpi_integer * out_quotient, u32 * out_remainder)
 263 {
 264
 265         ACPI_FUNCTION_TRACE(ut_short_divide);
 266
 267         /* Always check for a zero divisor */
 268
 269         if (divisor == 0) {
 270                 ACPI_ERROR((AE_INFO, "Divide by zero"));
 271                 return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO);
 272         }
 273
 274         /* Return only what was requested */
 275
 276         if (out_quotient) {
 277                 *out_quotient = in_dividend / divisor;
 278         }
 279         if (out_remainder) {
 280                 *out_remainder = (u32) (in_dividend % divisor);
 281         }
 282
 283         return_ACPI_STATUS(AE_OK);
 284 }
 285
 286 acpi_status
 287 acpi_ut_divide(acpi_integer in_dividend,
 288                acpi_integer in_divisor,
 289                acpi_integer * out_quotient, acpi_integer * out_remainder)
 290 {
 291         ACPI_FUNCTION_TRACE(ut_divide);
 292
 293         /* Always check for a zero divisor */
 294
 295         if (in_divisor == 0) {
 296                 ACPI_ERROR((AE_INFO, "Divide by zero"));
 297                 return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO);
 298         }
 299
 300         /* Return only what was requested */
 301
 302         if (out_quotient) {
 303                 *out_quotient = in_dividend / in_divisor;
 304         }
 305         if (out_remainder) {
 306                 *out_remainder = in_dividend % in_divisor;
 307         }
 308
 309         return_ACPI_STATUS(AE_OK);
 310 }
 311
 312 #endif