utmath.c

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/*******************************************************************************
 *
 * Module Name: utmath - Integer math support routines
 *
 ******************************************************************************/

/*
 * Copyright (C) 2000 - 2012, Intel Corp.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions, and the following disclaimer,
 *    without modification.
 * 2. Redistributions in binary form must reproduce at minimum a disclaimer
 *    substantially similar to the "NO WARRANTY" disclaimer below
 *    ("Disclaimer") and any redistribution must be conditioned upon
 *    including a substantially similar Disclaimer requirement for further
 *    binary redistribution.
 * 3. Neither the names of the above-listed copyright holders nor the names
 *    of any contributors may be used to endorse or promote products derived
 *    from this software without specific prior written permission.
 *
 * Alternatively, this software may be distributed under the terms of the
 * GNU General Public License ("GPL") version 2 as published by the Free
 * Software Foundation.
 *
 * NO WARRANTY
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * HOLDERS OR CONTRIBUTORS BE LIABLE FOR SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGES.
 */

#include <acpi/acpi.h>
#include "accommon.h"

#define _COMPONENT          ACPI_UTILITIES
ACPI_MODULE_NAME("utmath")

/*
 * Optional support for 64-bit double-precision integer divide. This code
 * is configurable and is implemented in order to support 32-bit kernel
 * environments where a 64-bit double-precision math library is not available.
 *
 * Support for a more normal 64-bit divide/modulo (with check for a divide-
 * by-zero) appears after this optional section of code.
 */
#ifndef ACPI_USE_NATIVE_DIVIDE
/* Structures used only for 64-bit divide */
typedef struct uint64_struct {
    u32 lo;
    u32 hi;

} uint64_struct;

typedef union uint64_overlay {
    u64 full;
    struct uint64_struct part;

} uint64_overlay;

/*******************************************************************************
 *
 * FUNCTION:    acpi_ut_short_divide
 *
 * PARAMETERS:  dividend            - 64-bit dividend
 *              divisor             - 32-bit divisor
 *              out_quotient        - Pointer to where the quotient is returned
 *              out_remainder       - Pointer to where the remainder is returned
 *
 * RETURN:      Status (Checks for divide-by-zero)
 *
 * DESCRIPTION: Perform a short (maximum 64 bits divided by 32 bits)
 *              divide and modulo.  The result is a 64-bit quotient and a
 *              32-bit remainder.
 *
 ******************************************************************************/

acpi_status
acpi_ut_short_divide(u64 dividend,
             u32 divisor, u64 *out_quotient, u32 *out_remainder)
{
    union uint64_overlay dividend_ovl;
    union uint64_overlay quotient;
    u32 remainder32;

    ACPI_FUNCTION_TRACE(ut_short_divide);

    /* Always check for a zero divisor */

    if (divisor == 0) {
        ACPI_ERROR((AE_INFO, "Divide by zero"));
        return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO);
    }

    dividend_ovl.full = dividend;

    /*
     * The quotient is 64 bits, the remainder is always 32 bits,
     * and is generated by the second divide.
     */
    ACPI_DIV_64_BY_32(0, dividend_ovl.part.hi, divisor,
              quotient.part.hi, remainder32);
    ACPI_DIV_64_BY_32(remainder32, dividend_ovl.part.lo, divisor,
              quotient.part.lo, remainder32);

    /* Return only what was requested */

    if (out_quotient) {
        *out_quotient = quotient.full;
    }
    if (out_remainder) {
        *out_remainder = remainder32;
    }

    return_ACPI_STATUS(AE_OK);
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_ut_divide
 *
 * PARAMETERS:  in_dividend         - Dividend
 *              in_divisor          - Divisor
 *              out_quotient        - Pointer to where the quotient is returned
 *              out_remainder       - Pointer to where the remainder is returned
 *
 * RETURN:      Status (Checks for divide-by-zero)
 *
 * DESCRIPTION: Perform a divide and modulo.
 *
 ******************************************************************************/

acpi_status
acpi_ut_divide(u64 in_dividend,
           u64 in_divisor, u64 *out_quotient, u64 *out_remainder)
{
    union uint64_overlay dividend;
    union uint64_overlay divisor;
    union uint64_overlay quotient;
    union uint64_overlay remainder;
    union uint64_overlay normalized_dividend;
    union uint64_overlay normalized_divisor;
    u32 partial1;
    union uint64_overlay partial2;
    union uint64_overlay partial3;

    ACPI_FUNCTION_TRACE(ut_divide);

    /* Always check for a zero divisor */

    if (in_divisor == 0) {
        ACPI_ERROR((AE_INFO, "Divide by zero"));
        return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO);
    }

    divisor.full = in_divisor;
    dividend.full = in_dividend;
    if (divisor.part.hi == 0) {
        /*
         * 1) Simplest case is where the divisor is 32 bits, we can
         * just do two divides
         */
        remainder.part.hi = 0;

        /*
         * The quotient is 64 bits, the remainder is always 32 bits,
         * and is generated by the second divide.
         */
        ACPI_DIV_64_BY_32(0, dividend.part.hi, divisor.part.lo,
                  quotient.part.hi, partial1);
        ACPI_DIV_64_BY_32(partial1, dividend.part.lo, divisor.part.lo,
                  quotient.part.lo, remainder.part.lo);
    }

    else {
        /*
         * 2) The general case where the divisor is a full 64 bits
         * is more difficult
         */
        quotient.part.hi = 0;
        normalized_dividend = dividend;
        normalized_divisor = divisor;

        /* Normalize the operands (shift until the divisor is < 32 bits) */

        do {
            ACPI_SHIFT_RIGHT_64(normalized_divisor.part.hi,
                        normalized_divisor.part.lo);
            ACPI_SHIFT_RIGHT_64(normalized_dividend.part.hi,
                        normalized_dividend.part.lo);

        } while (normalized_divisor.part.hi != 0);

        /* Partial divide */

        ACPI_DIV_64_BY_32(normalized_dividend.part.hi,
                  normalized_dividend.part.lo,
                  normalized_divisor.part.lo,
                  quotient.part.lo, partial1);

        /*
         * The quotient is always 32 bits, and simply requires adjustment.
         * The 64-bit remainder must be generated.
         */
        partial1 = quotient.part.lo * divisor.part.hi;
        partial2.full = (u64) quotient.part.lo * divisor.part.lo;
        partial3.full = (u64) partial2.part.hi + partial1;

        remainder.part.hi = partial3.part.lo;
        remainder.part.lo = partial2.part.lo;

        if (partial3.part.hi == 0) {
            if (partial3.part.lo >= dividend.part.hi) {
                if (partial3.part.lo == dividend.part.hi) {
                    if (partial2.part.lo > dividend.part.lo) {
                        quotient.part.lo--;
                        remainder.full -= divisor.full;
                    }
                } else {
                    quotient.part.lo--;
                    remainder.full -= divisor.full;
                }
            }

            remainder.full = remainder.full - dividend.full;
            remainder.part.hi = (u32) - ((s32) remainder.part.hi);
            remainder.part.lo = (u32) - ((s32) remainder.part.lo);

            if (remainder.part.lo) {
                remainder.part.hi--;
            }
        }
    }

    /* Return only what was requested */

    if (out_quotient) {
        *out_quotient = quotient.full;
    }
    if (out_remainder) {
        *out_remainder = remainder.full;
    }

    return_ACPI_STATUS(AE_OK);
}

#else
/*******************************************************************************
 *
 * FUNCTION:    acpi_ut_short_divide, acpi_ut_divide
 *
 * PARAMETERS:  See function headers above
 *
 * DESCRIPTION: Native versions of the ut_divide functions. Use these if either
 *              1) The target is a 64-bit platform and therefore 64-bit
 *                 integer math is supported directly by the machine.
 *              2) The target is a 32-bit or 16-bit platform, and the
 *                 double-precision integer math library is available to
 *                 perform the divide.
 *
 ******************************************************************************/
acpi_status
acpi_ut_short_divide(u64 in_dividend,
             u32 divisor, u64 *out_quotient, u32 *out_remainder)
{

    ACPI_FUNCTION_TRACE(ut_short_divide);

    /* Always check for a zero divisor */

    if (divisor == 0) {
        ACPI_ERROR((AE_INFO, "Divide by zero"));
        return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO);
    }

    /* Return only what was requested */

    if (out_quotient) {
        *out_quotient = in_dividend / divisor;
    }
    if (out_remainder) {
        *out_remainder = (u32) (in_dividend % divisor);
    }

    return_ACPI_STATUS(AE_OK);
}

acpi_status
acpi_ut_divide(u64 in_dividend,
           u64 in_divisor, u64 *out_quotient, u64 *out_remainder)
{
    ACPI_FUNCTION_TRACE(ut_divide);

    /* Always check for a zero divisor */

    if (in_divisor == 0) {
        ACPI_ERROR((AE_INFO, "Divide by zero"));
        return_ACPI_STATUS(AE_AML_DIVIDE_BY_ZERO);
    }

    /* Return only what was requested */

    if (out_quotient) {
        *out_quotient = in_dividend / in_divisor;
    }
    if (out_remainder) {
        *out_remainder = in_dividend % in_divisor;
    }

    return_ACPI_STATUS(AE_OK);
}

#endif