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
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
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
acpi_ut_divide(u64 in_dividend,u64 in_divisor,u64 * out_quotient,u64 * out_remainder)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