325 lines
9.4 KiB
C
325 lines
9.4 KiB
C
/*******************************************************************************
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*
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* Module Name: utmath - Integer math support routines
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*
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******************************************************************************/
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/*
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* Copyright (C) 2000 - 2013, Intel Corp.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions, and the following disclaimer,
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* without modification.
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* 2. Redistributions in binary form must reproduce at minimum a disclaimer
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* substantially similar to the "NO WARRANTY" disclaimer below
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* ("Disclaimer") and any redistribution must be conditioned upon
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* including a substantially similar Disclaimer requirement for further
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* binary redistribution.
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* 3. Neither the names of the above-listed copyright holders nor the names
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* of any contributors may be used to endorse or promote products derived
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* from this software without specific prior written permission.
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*
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* Alternatively, this software may be distributed under the terms of the
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* GNU General Public License ("GPL") version 2 as published by the Free
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* Software Foundation.
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*
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* NO WARRANTY
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR
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* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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* HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
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* IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGES.
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*/
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#include <acpi/acpi.h>
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#include "accommon.h"
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#define _COMPONENT ACPI_UTILITIES
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ACPI_MODULE_NAME("utmath")
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/*
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* Optional support for 64-bit double-precision integer divide. This code
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* is configurable and is implemented in order to support 32-bit kernel
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* environments where a 64-bit double-precision math library is not available.
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*
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* Support for a more normal 64-bit divide/modulo (with check for a divide-
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* by-zero) appears after this optional section of code.
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*/
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#ifndef ACPI_USE_NATIVE_DIVIDE
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/* Structures used only for 64-bit divide */
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typedef struct uint64_struct {
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u32 lo;
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u32 hi;
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} uint64_struct;
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typedef union uint64_overlay {
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u64 full;
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struct uint64_struct part;
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} uint64_overlay;
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/*******************************************************************************
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*
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* FUNCTION: acpi_ut_short_divide
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*
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* PARAMETERS: dividend - 64-bit dividend
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* divisor - 32-bit divisor
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* out_quotient - Pointer to where the quotient is returned
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* out_remainder - Pointer to where the remainder is returned
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*
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* RETURN: Status (Checks for divide-by-zero)
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*
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* DESCRIPTION: Perform a short (maximum 64 bits divided by 32 bits)
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* divide and modulo. The result is a 64-bit quotient and a
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* 32-bit remainder.
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*
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******************************************************************************/
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acpi_status
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acpi_ut_short_divide(u64 dividend,
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u32 divisor, u64 *out_quotient, u32 *out_remainder)
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{
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union uint64_overlay dividend_ovl;
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union uint64_overlay quotient;
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u32 remainder32;
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ACPI_FUNCTION_TRACE(ut_short_divide);
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/* Always check for a zero divisor */
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if (divisor == 0) {
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ACPI_ERROR((AE_INFO, "Divide by zero"));
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return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO);
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}
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dividend_ovl.full = dividend;
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/*
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* The quotient is 64 bits, the remainder is always 32 bits,
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* and is generated by the second divide.
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*/
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ACPI_DIV_64_BY_32(0, dividend_ovl.part.hi, divisor,
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quotient.part.hi, remainder32);
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ACPI_DIV_64_BY_32(remainder32, dividend_ovl.part.lo, divisor,
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quotient.part.lo, remainder32);
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/* Return only what was requested */
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if (out_quotient) {
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*out_quotient = quotient.full;
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}
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if (out_remainder) {
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*out_remainder = remainder32;
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}
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return_ACPI_STATUS(AE_OK);
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}
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/*******************************************************************************
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*
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* FUNCTION: acpi_ut_divide
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*
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* PARAMETERS: in_dividend - Dividend
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* in_divisor - Divisor
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* out_quotient - Pointer to where the quotient is returned
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* out_remainder - Pointer to where the remainder is returned
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*
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* RETURN: Status (Checks for divide-by-zero)
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*
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* DESCRIPTION: Perform a divide and modulo.
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*
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******************************************************************************/
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acpi_status
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acpi_ut_divide(u64 in_dividend,
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u64 in_divisor, u64 *out_quotient, u64 *out_remainder)
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{
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union uint64_overlay dividend;
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union uint64_overlay divisor;
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union uint64_overlay quotient;
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union uint64_overlay remainder;
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union uint64_overlay normalized_dividend;
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union uint64_overlay normalized_divisor;
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u32 partial1;
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union uint64_overlay partial2;
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union uint64_overlay partial3;
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ACPI_FUNCTION_TRACE(ut_divide);
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/* Always check for a zero divisor */
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if (in_divisor == 0) {
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ACPI_ERROR((AE_INFO, "Divide by zero"));
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return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO);
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}
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divisor.full = in_divisor;
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dividend.full = in_dividend;
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if (divisor.part.hi == 0) {
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/*
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* 1) Simplest case is where the divisor is 32 bits, we can
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* just do two divides
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*/
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remainder.part.hi = 0;
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/*
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* The quotient is 64 bits, the remainder is always 32 bits,
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* and is generated by the second divide.
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*/
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ACPI_DIV_64_BY_32(0, dividend.part.hi, divisor.part.lo,
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quotient.part.hi, partial1);
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ACPI_DIV_64_BY_32(partial1, dividend.part.lo, divisor.part.lo,
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quotient.part.lo, remainder.part.lo);
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}
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else {
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/*
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* 2) The general case where the divisor is a full 64 bits
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* is more difficult
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*/
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quotient.part.hi = 0;
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normalized_dividend = dividend;
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normalized_divisor = divisor;
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/* Normalize the operands (shift until the divisor is < 32 bits) */
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do {
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ACPI_SHIFT_RIGHT_64(normalized_divisor.part.hi,
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normalized_divisor.part.lo);
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ACPI_SHIFT_RIGHT_64(normalized_dividend.part.hi,
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normalized_dividend.part.lo);
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} while (normalized_divisor.part.hi != 0);
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/* Partial divide */
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ACPI_DIV_64_BY_32(normalized_dividend.part.hi,
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normalized_dividend.part.lo,
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normalized_divisor.part.lo,
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quotient.part.lo, partial1);
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/*
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* The quotient is always 32 bits, and simply requires adjustment.
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* The 64-bit remainder must be generated.
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*/
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partial1 = quotient.part.lo * divisor.part.hi;
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partial2.full = (u64) quotient.part.lo * divisor.part.lo;
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partial3.full = (u64) partial2.part.hi + partial1;
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remainder.part.hi = partial3.part.lo;
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remainder.part.lo = partial2.part.lo;
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if (partial3.part.hi == 0) {
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if (partial3.part.lo >= dividend.part.hi) {
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if (partial3.part.lo == dividend.part.hi) {
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if (partial2.part.lo > dividend.part.lo) {
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quotient.part.lo--;
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remainder.full -= divisor.full;
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}
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} else {
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quotient.part.lo--;
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remainder.full -= divisor.full;
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}
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}
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remainder.full = remainder.full - dividend.full;
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remainder.part.hi = (u32) - ((s32) remainder.part.hi);
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remainder.part.lo = (u32) - ((s32) remainder.part.lo);
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if (remainder.part.lo) {
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remainder.part.hi--;
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}
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}
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}
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/* Return only what was requested */
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if (out_quotient) {
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*out_quotient = quotient.full;
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}
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if (out_remainder) {
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*out_remainder = remainder.full;
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}
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return_ACPI_STATUS(AE_OK);
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}
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#else
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/*******************************************************************************
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*
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* FUNCTION: acpi_ut_short_divide, acpi_ut_divide
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*
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* PARAMETERS: See function headers above
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*
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* DESCRIPTION: Native versions of the ut_divide functions. Use these if either
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* 1) The target is a 64-bit platform and therefore 64-bit
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* integer math is supported directly by the machine.
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* 2) The target is a 32-bit or 16-bit platform, and the
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* double-precision integer math library is available to
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* perform the divide.
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*
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******************************************************************************/
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acpi_status
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acpi_ut_short_divide(u64 in_dividend,
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u32 divisor, u64 *out_quotient, u32 *out_remainder)
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{
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ACPI_FUNCTION_TRACE(ut_short_divide);
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/* Always check for a zero divisor */
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if (divisor == 0) {
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ACPI_ERROR((AE_INFO, "Divide by zero"));
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return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO);
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}
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/* Return only what was requested */
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if (out_quotient) {
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*out_quotient = in_dividend / divisor;
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}
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if (out_remainder) {
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*out_remainder = (u32) (in_dividend % divisor);
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}
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return_ACPI_STATUS(AE_OK);
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}
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acpi_status
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acpi_ut_divide(u64 in_dividend,
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u64 in_divisor, u64 *out_quotient, u64 *out_remainder)
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{
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ACPI_FUNCTION_TRACE(ut_divide);
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/* Always check for a zero divisor */
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if (in_divisor == 0) {
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ACPI_ERROR((AE_INFO, "Divide by zero"));
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return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO);
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}
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/* Return only what was requested */
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if (out_quotient) {
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*out_quotient = in_dividend / in_divisor;
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}
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if (out_remainder) {
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*out_remainder = in_dividend % in_divisor;
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}
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return_ACPI_STATUS(AE_OK);
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}
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#endif
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