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 327