drivers/acpi/acpica/utmath.c

   1 /*******************************************************************************
   2  *
   3  * Module Name: utmath - Integer math support routines
   4  *
   5  ******************************************************************************/
   6
   7 /*
   8  * Copyright (C) 2000 - 2016, 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  * Optional support for 64-bit double-precision integer divide. This code
  52  * is configurable and is implemented in order to support 32-bit kernel
  53  * environments where a 64-bit double-precision math library is not available.
  54  *
  55  * Support for a more normal 64-bit divide/modulo (with check for a divide-
  56  * by-zero) appears after this optional section of code.
  57  */
  58 #ifndef ACPI_USE_NATIVE_DIVIDE
  59 /* Structures used only for 64-bit divide */
  60 typedef struct uint64_struct {
  61         u32 lo;
  62         u32 hi;
  63
  64 } uint64_struct;
  65
  66 typedef union uint64_overlay {
  67         u64 full;
  68         struct uint64_struct part;
  69
  70 } uint64_overlay;
  71
  72 /*******************************************************************************
  73  *
  74  * FUNCTION:    acpi_ut_short_divide
  75  *
  76  * PARAMETERS:  dividend            - 64-bit dividend
  77  *              divisor             - 32-bit divisor
  78  *              out_quotient        - Pointer to where the quotient is returned
  79  *              out_remainder       - Pointer to where the remainder is returned
  80  *
  81  * RETURN:      Status (Checks for divide-by-zero)
  82  *
  83  * DESCRIPTION: Perform a short (maximum 64 bits divided by 32 bits)
  84  *              divide and modulo. The result is a 64-bit quotient and a
  85  *              32-bit remainder.
  86  *
  87  ******************************************************************************/
  88
  89 acpi_status
  90 acpi_ut_short_divide(u64 dividend,
  91                      u32 divisor, u64 *out_quotient, u32 *out_remainder)
  92 {
  93         union uint64_overlay dividend_ovl;
  94         union uint64_overlay quotient;
  95         u32 remainder32;
  96
  97         ACPI_FUNCTION_TRACE(ut_short_divide);
  98
  99         /* Always check for a zero divisor */
 100
 101         if (divisor == 0) {
 102                 ACPI_ERROR((AE_INFO, "Divide by zero"));
 103                 return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO);
 104         }
 105
 106         dividend_ovl.full = dividend;
 107
 108         /*
 109          * The quotient is 64 bits, the remainder is always 32 bits,
 110          * and is generated by the second divide.
 111          */
 112         ACPI_DIV_64_BY_32(0, dividend_ovl.part.hi, divisor,
 113                           quotient.part.hi, remainder32);
 114
 115         ACPI_DIV_64_BY_32(remainder32, dividend_ovl.part.lo, divisor,
 116                           quotient.part.lo, remainder32);
 117
 118         /* Return only what was requested */
 119
 120         if (out_quotient) {
 121                 *out_quotient = quotient.full;
 122         }
 123         if (out_remainder) {
 124                 *out_remainder = remainder32;
 125         }
 126
 127         return_ACPI_STATUS(AE_OK);
 128 }
 129
 130 /*******************************************************************************
 131  *
 132  * FUNCTION:    acpi_ut_divide
 133  *
 134  * PARAMETERS:  in_dividend         - Dividend
 135  *              in_divisor          - Divisor
 136  *              out_quotient        - Pointer to where the quotient is returned
 137  *              out_remainder       - Pointer to where the remainder is returned
 138  *
 139  * RETURN:      Status (Checks for divide-by-zero)
 140  *
 141  * DESCRIPTION: Perform a divide and modulo.
 142  *
 143  ******************************************************************************/
 144
 145 acpi_status
 146 acpi_ut_divide(u64 in_dividend,
 147                u64 in_divisor, u64 *out_quotient, u64 *out_remainder)
 148 {
 149         union uint64_overlay dividend;
 150         union uint64_overlay divisor;
 151         union uint64_overlay quotient;
 152         union uint64_overlay remainder;
 153         union uint64_overlay normalized_dividend;
 154         union uint64_overlay normalized_divisor;
 155         u32 partial1;
 156         union uint64_overlay partial2;
 157         union uint64_overlay partial3;
 158
 159         ACPI_FUNCTION_TRACE(ut_divide);
 160
 161         /* Always check for a zero divisor */
 162
 163         if (in_divisor == 0) {
 164                 ACPI_ERROR((AE_INFO, "Divide by zero"));
 165                 return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO);
 166         }
 167
 168         divisor.full = in_divisor;
 169         dividend.full = in_dividend;
 170         if (divisor.part.hi == 0) {
 171                 /*
 172                  * 1) Simplest case is where the divisor is 32 bits, we can
 173                  * just do two divides
 174                  */
 175                 remainder.part.hi = 0;
 176
 177                 /*
 178                  * The quotient is 64 bits, the remainder is always 32 bits,
 179                  * and is generated by the second divide.
 180                  */
 181                 ACPI_DIV_64_BY_32(0, dividend.part.hi, divisor.part.lo,
 182                                   quotient.part.hi, partial1);
 183
 184                 ACPI_DIV_64_BY_32(partial1, dividend.part.lo, divisor.part.lo,
 185                                   quotient.part.lo, remainder.part.lo);
 186         }
 187
 188         else {
 189                 /*
 190                  * 2) The general case where the divisor is a full 64 bits
 191                  * is more difficult
 192                  */
 193                 quotient.part.hi = 0;
 194                 normalized_dividend = dividend;
 195                 normalized_divisor = divisor;
 196
 197                 /* Normalize the operands (shift until the divisor is < 32 bits) */
 198
 199                 do {
 200                         ACPI_SHIFT_RIGHT_64(normalized_divisor.part.hi,
 201                                             normalized_divisor.part.lo);
 202                         ACPI_SHIFT_RIGHT_64(normalized_dividend.part.hi,
 203                                             normalized_dividend.part.lo);
 204
 205                 } while (normalized_divisor.part.hi != 0);
 206
 207                 /* Partial divide */
 208
 209                 ACPI_DIV_64_BY_32(normalized_dividend.part.hi,
 210                                   normalized_dividend.part.lo,
 211                                   normalized_divisor.part.lo, quotient.part.lo,
 212                                   partial1);
 213
 214                 /*
 215                  * The quotient is always 32 bits, and simply requires
 216                  * adjustment. The 64-bit remainder must be generated.
 217                  */
 218                 partial1 = quotient.part.lo * divisor.part.hi;
 219                 partial2.full = (u64) quotient.part.lo * divisor.part.lo;
 220                 partial3.full = (u64) partial2.part.hi + partial1;
 221
 222                 remainder.part.hi = partial3.part.lo;
 223                 remainder.part.lo = partial2.part.lo;
 224
 225                 if (partial3.part.hi == 0) {
 226                         if (partial3.part.lo >= dividend.part.hi) {
 227                                 if (partial3.part.lo == dividend.part.hi) {
 228                                         if (partial2.part.lo > dividend.part.lo) {
 229                                                 quotient.part.lo--;
 230                                                 remainder.full -= divisor.full;
 231                                         }
 232                                 } else {
 233                                         quotient.part.lo--;
 234                                         remainder.full -= divisor.full;
 235                                 }
 236                         }
 237
 238                         remainder.full = remainder.full - dividend.full;
 239                         remainder.part.hi = (u32) - ((s32) remainder.part.hi);
 240                         remainder.part.lo = (u32) - ((s32) remainder.part.lo);
 241
 242                         if (remainder.part.lo) {
 243                                 remainder.part.hi--;
 244                         }
 245                 }
 246         }
 247
 248         /* Return only what was requested */
 249
 250         if (out_quotient) {
 251                 *out_quotient = quotient.full;
 252         }
 253         if (out_remainder) {
 254                 *out_remainder = remainder.full;
 255         }
 256
 257         return_ACPI_STATUS(AE_OK);
 258 }
 259
 260 #else
 261 /*******************************************************************************
 262  *
 263  * FUNCTION:    acpi_ut_short_divide, acpi_ut_divide
 264  *
 265  * PARAMETERS:  See function headers above
 266  *
 267  * DESCRIPTION: Native versions of the ut_divide functions. Use these if either
 268  *              1) The target is a 64-bit platform and therefore 64-bit
 269  *                 integer math is supported directly by the machine.
 270  *              2) The target is a 32-bit or 16-bit platform, and the
 271  *                 double-precision integer math library is available to
 272  *                 perform the divide.
 273  *
 274  ******************************************************************************/
 275 acpi_status
 276 acpi_ut_short_divide(u64 in_dividend,
 277                      u32 divisor, u64 *out_quotient, u32 *out_remainder)
 278 {
 279
 280         ACPI_FUNCTION_TRACE(ut_short_divide);
 281
 282         /* Always check for a zero divisor */
 283
 284         if (divisor == 0) {
 285                 ACPI_ERROR((AE_INFO, "Divide by zero"));
 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(u64 in_dividend,
 303                u64 in_divisor, u64 *out_quotient, u64 *out_remainder)
 304 {
 305         ACPI_FUNCTION_TRACE(ut_divide);
 306
 307         /* Always check for a zero divisor */
 308
 309         if (in_divisor == 0) {
 310                 ACPI_ERROR((AE_INFO, "Divide by zero"));
 311                 return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO);
 312         }
 313
 314         /* Return only what was requested */
 315
 316         if (out_quotient) {
 317                 *out_quotient = in_dividend / in_divisor;
 318         }
 319         if (out_remainder) {
 320                 *out_remainder = in_dividend % in_divisor;
 321         }
 322
 323         return_ACPI_STATUS(AE_OK);
 324 }
 325
 326 #endif