1/*******************************************************************************
2 *
3 * Module Name: utmath - Integer math support routines
4 *
5 ******************************************************************************/
6
7/*
8 * Copyright (C) 2000 - 2014, 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
48ACPI_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 */
60typedef struct uint64_struct {
61	u32 lo;
62	u32 hi;
63
64} uint64_struct;
65
66typedef 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
89acpi_status
90acpi_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
144acpi_status
145acpi_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 ******************************************************************************/
273acpi_status
274acpi_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
299acpi_status
300acpi_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