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 308