1 /******************************************************************************* 2 * 3 * Module Name: utmath - Integer math support routines 4 * 5 ******************************************************************************/ 6 7 /* 8 * Copyright (C) 2000 - 2015, 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 ACPI_DIV_64_BY_32(remainder32, dividend_ovl.part.lo, divisor, 115 quotient.part.lo, remainder32); 116 117 /* Return only what was requested */ 118 119 if (out_quotient) { 120 *out_quotient = quotient.full; 121 } 122 if (out_remainder) { 123 *out_remainder = remainder32; 124 } 125 126 return_ACPI_STATUS(AE_OK); 127 } 128 129 /******************************************************************************* 130 * 131 * FUNCTION: acpi_ut_divide 132 * 133 * PARAMETERS: in_dividend - Dividend 134 * in_divisor - Divisor 135 * out_quotient - Pointer to where the quotient is returned 136 * out_remainder - Pointer to where the remainder is returned 137 * 138 * RETURN: Status (Checks for divide-by-zero) 139 * 140 * DESCRIPTION: Perform a divide and modulo. 141 * 142 ******************************************************************************/ 143 144 acpi_status 145 acpi_ut_divide(u64 in_dividend, 146 u64 in_divisor, u64 *out_quotient, u64 *out_remainder) 147 { 148 union uint64_overlay dividend; 149 union uint64_overlay divisor; 150 union uint64_overlay quotient; 151 union uint64_overlay remainder; 152 union uint64_overlay normalized_dividend; 153 union uint64_overlay normalized_divisor; 154 u32 partial1; 155 union uint64_overlay partial2; 156 union uint64_overlay partial3; 157 158 ACPI_FUNCTION_TRACE(ut_divide); 159 160 /* Always check for a zero divisor */ 161 162 if (in_divisor == 0) { 163 ACPI_ERROR((AE_INFO, "Divide by zero")); 164 return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO); 165 } 166 167 divisor.full = in_divisor; 168 dividend.full = in_dividend; 169 if (divisor.part.hi == 0) { 170 /* 171 * 1) Simplest case is where the divisor is 32 bits, we can 172 * just do two divides 173 */ 174 remainder.part.hi = 0; 175 176 /* 177 * The quotient is 64 bits, the remainder is always 32 bits, 178 * and is generated by the second divide. 179 */ 180 ACPI_DIV_64_BY_32(0, dividend.part.hi, divisor.part.lo, 181 quotient.part.hi, partial1); 182 ACPI_DIV_64_BY_32(partial1, dividend.part.lo, divisor.part.lo, 183 quotient.part.lo, remainder.part.lo); 184 } 185 186 else { 187 /* 188 * 2) The general case where the divisor is a full 64 bits 189 * is more difficult 190 */ 191 quotient.part.hi = 0; 192 normalized_dividend = dividend; 193 normalized_divisor = divisor; 194 195 /* Normalize the operands (shift until the divisor is < 32 bits) */ 196 197 do { 198 ACPI_SHIFT_RIGHT_64(normalized_divisor.part.hi, 199 normalized_divisor.part.lo); 200 ACPI_SHIFT_RIGHT_64(normalized_dividend.part.hi, 201 normalized_dividend.part.lo); 202 203 } while (normalized_divisor.part.hi != 0); 204 205 /* Partial divide */ 206 207 ACPI_DIV_64_BY_32(normalized_dividend.part.hi, 208 normalized_dividend.part.lo, 209 normalized_divisor.part.lo, 210 quotient.part.lo, partial1); 211 212 /* 213 * The quotient is always 32 bits, and simply requires adjustment. 214 * The 64-bit remainder must be generated. 215 */ 216 partial1 = quotient.part.lo * divisor.part.hi; 217 partial2.full = (u64) quotient.part.lo * divisor.part.lo; 218 partial3.full = (u64) partial2.part.hi + partial1; 219 220 remainder.part.hi = partial3.part.lo; 221 remainder.part.lo = partial2.part.lo; 222 223 if (partial3.part.hi == 0) { 224 if (partial3.part.lo >= dividend.part.hi) { 225 if (partial3.part.lo == dividend.part.hi) { 226 if (partial2.part.lo > dividend.part.lo) { 227 quotient.part.lo--; 228 remainder.full -= divisor.full; 229 } 230 } else { 231 quotient.part.lo--; 232 remainder.full -= divisor.full; 233 } 234 } 235 236 remainder.full = remainder.full - dividend.full; 237 remainder.part.hi = (u32) - ((s32) remainder.part.hi); 238 remainder.part.lo = (u32) - ((s32) remainder.part.lo); 239 240 if (remainder.part.lo) { 241 remainder.part.hi--; 242 } 243 } 244 } 245 246 /* Return only what was requested */ 247 248 if (out_quotient) { 249 *out_quotient = quotient.full; 250 } 251 if (out_remainder) { 252 *out_remainder = remainder.full; 253 } 254 255 return_ACPI_STATUS(AE_OK); 256 } 257 258 #else 259 /******************************************************************************* 260 * 261 * FUNCTION: acpi_ut_short_divide, acpi_ut_divide 262 * 263 * PARAMETERS: See function headers above 264 * 265 * DESCRIPTION: Native versions of the ut_divide functions. Use these if either 266 * 1) The target is a 64-bit platform and therefore 64-bit 267 * integer math is supported directly by the machine. 268 * 2) The target is a 32-bit or 16-bit platform, and the 269 * double-precision integer math library is available to 270 * perform the divide. 271 * 272 ******************************************************************************/ 273 acpi_status 274 acpi_ut_short_divide(u64 in_dividend, 275 u32 divisor, u64 *out_quotient, u32 *out_remainder) 276 { 277 278 ACPI_FUNCTION_TRACE(ut_short_divide); 279 280 /* Always check for a zero divisor */ 281 282 if (divisor == 0) { 283 ACPI_ERROR((AE_INFO, "Divide by zero")); 284 return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO); 285 } 286 287 /* Return only what was requested */ 288 289 if (out_quotient) { 290 *out_quotient = in_dividend / divisor; 291 } 292 if (out_remainder) { 293 *out_remainder = (u32) (in_dividend % divisor); 294 } 295 296 return_ACPI_STATUS(AE_OK); 297 } 298 299 acpi_status 300 acpi_ut_divide(u64 in_dividend, 301 u64 in_divisor, u64 *out_quotient, u64 *out_remainder) 302 { 303 ACPI_FUNCTION_TRACE(ut_divide); 304 305 /* Always check for a zero divisor */ 306 307 if (in_divisor == 0) { 308 ACPI_ERROR((AE_INFO, "Divide by zero")); 309 return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO); 310 } 311 312 /* Return only what was requested */ 313 314 if (out_quotient) { 315 *out_quotient = in_dividend / in_divisor; 316 } 317 if (out_remainder) { 318 *out_remainder = in_dividend % in_divisor; 319 } 320 321 return_ACPI_STATUS(AE_OK); 322 } 323 324 #endif 325