1 /*******************************************************************************
3 * Module Name: utmath - Integer math support routines
5 ******************************************************************************/
8 * Copyright (C) 2000 - 2012, Intel Corp.
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44 #include <acpi/acpi.h>
47 #define _COMPONENT ACPI_UTILITIES
48 ACPI_MODULE_NAME("utmath")
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.
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.
58 #ifndef ACPI_USE_NATIVE_DIVIDE
59 /* Structures used only for 64-bit divide */
60 typedef struct uint64_struct {
66 typedef union uint64_overlay {
68 struct uint64_struct part;
72 /*******************************************************************************
74 * FUNCTION: acpi_ut_short_divide
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
81 * RETURN: Status (Checks for divide-by-zero)
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
87 ******************************************************************************/
90 acpi_ut_short_divide(u64 dividend,
91 u32 divisor, u64 *out_quotient, u32 *out_remainder)
93 union uint64_overlay dividend_ovl;
94 union uint64_overlay quotient;
97 ACPI_FUNCTION_TRACE(ut_short_divide);
99 /* Always check for a zero divisor */
102 ACPI_ERROR((AE_INFO, "Divide by zero"));
103 return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO);
106 dividend_ovl.full = dividend;
109 * The quotient is 64 bits, the remainder is always 32 bits,
110 * and is generated by the second divide.
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);
117 /* Return only what was requested */
120 *out_quotient = quotient.full;
123 *out_remainder = remainder32;
126 return_ACPI_STATUS(AE_OK);
129 /*******************************************************************************
131 * FUNCTION: acpi_ut_divide
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
138 * RETURN: Status (Checks for divide-by-zero)
140 * DESCRIPTION: Perform a divide and modulo.
142 ******************************************************************************/
145 acpi_ut_divide(u64 in_dividend,
146 u64 in_divisor, u64 *out_quotient, u64 *out_remainder)
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;
155 union uint64_overlay partial2;
156 union uint64_overlay partial3;
158 ACPI_FUNCTION_TRACE(ut_divide);
160 /* Always check for a zero divisor */
162 if (in_divisor == 0) {
163 ACPI_ERROR((AE_INFO, "Divide by zero"));
164 return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO);
167 divisor.full = in_divisor;
168 dividend.full = in_dividend;
169 if (divisor.part.hi == 0) {
171 * 1) Simplest case is where the divisor is 32 bits, we can
172 * just do two divides
174 remainder.part.hi = 0;
177 * The quotient is 64 bits, the remainder is always 32 bits,
178 * and is generated by the second divide.
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);
188 * 2) The general case where the divisor is a full 64 bits
191 quotient.part.hi = 0;
192 normalized_dividend = dividend;
193 normalized_divisor = divisor;
195 /* Normalize the operands (shift until the divisor is < 32 bits) */
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);
203 } while (normalized_divisor.part.hi != 0);
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);
213 * The quotient is always 32 bits, and simply requires adjustment.
214 * The 64-bit remainder must be generated.
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;
220 remainder.part.hi = partial3.part.lo;
221 remainder.part.lo = partial2.part.lo;
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) {
228 remainder.full -= divisor.full;
232 remainder.full -= divisor.full;
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);
240 if (remainder.part.lo) {
246 /* Return only what was requested */
249 *out_quotient = quotient.full;
252 *out_remainder = remainder.full;
255 return_ACPI_STATUS(AE_OK);
259 /*******************************************************************************
261 * FUNCTION: acpi_ut_short_divide, acpi_ut_divide
263 * PARAMETERS: See function headers above
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.
272 ******************************************************************************/
274 acpi_ut_short_divide(u64 in_dividend,
275 u32 divisor, u64 *out_quotient, u32 *out_remainder)
278 ACPI_FUNCTION_TRACE(ut_short_divide);
280 /* Always check for a zero divisor */
283 ACPI_ERROR((AE_INFO, "Divide by zero"));
284 return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO);
287 /* Return only what was requested */
290 *out_quotient = in_dividend / divisor;
293 *out_remainder = (u32) (in_dividend % divisor);
296 return_ACPI_STATUS(AE_OK);
300 acpi_ut_divide(u64 in_dividend,
301 u64 in_divisor, u64 *out_quotient, u64 *out_remainder)
303 ACPI_FUNCTION_TRACE(ut_divide);
305 /* Always check for a zero divisor */
307 if (in_divisor == 0) {
308 ACPI_ERROR((AE_INFO, "Divide by zero"));
309 return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO);
312 /* Return only what was requested */
315 *out_quotient = in_dividend / in_divisor;
318 *out_remainder = in_dividend % in_divisor;
321 return_ACPI_STATUS(AE_OK);