1 /*******************************************************************************
2 *
3 * Module Name: utmath - Integer math support routines
4 *
5 ******************************************************************************/
6
7 /*
8 * Copyright (C) 2000 - 2011, 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
acpi_ut_short_divide(u64 dividend,u32 divisor,u64 * out_quotient,u32 * out_remainder)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
acpi_ut_divide(u64 in_dividend,u64 in_divisor,u64 * out_quotient,u64 * out_remainder)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