tbfadt.c

Go to the documentation of this file.

/******************************************************************************
 *
 * Module Name: tbfadt   - FADT table utilities
 *
 *****************************************************************************/

/*
 * 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"
#include "actables.h"

#define _COMPONENT          ACPI_TABLES
ACPI_MODULE_NAME("tbfadt")

/* Local prototypes */
static void
acpi_tb_init_generic_address(struct acpi_generic_address *generic_address,
                 u8 space_id,
                 u8 byte_width, u64 address, char *register_name);

static void acpi_tb_convert_fadt(void);

static void acpi_tb_validate_fadt(void);

static void acpi_tb_setup_fadt_registers(void);

/* Table for conversion of FADT to common internal format and FADT validation */

typedef struct acpi_fadt_info {
    char *name;
    u16 address64;
    u16 address32;
    u16 length;
    u8 default_length;
    u8 type;

} acpi_fadt_info;

#define ACPI_FADT_OPTIONAL          0
#define ACPI_FADT_REQUIRED          1
#define ACPI_FADT_SEPARATE_LENGTH   2

static struct acpi_fadt_info fadt_info_table[] = {
    {"Pm1aEventBlock",
     ACPI_FADT_OFFSET(xpm1a_event_block),
     ACPI_FADT_OFFSET(pm1a_event_block),
     ACPI_FADT_OFFSET(pm1_event_length),
     ACPI_PM1_REGISTER_WIDTH * 2,   /* Enable + Status register */
     ACPI_FADT_REQUIRED},

    {"Pm1bEventBlock",
     ACPI_FADT_OFFSET(xpm1b_event_block),
     ACPI_FADT_OFFSET(pm1b_event_block),
     ACPI_FADT_OFFSET(pm1_event_length),
     ACPI_PM1_REGISTER_WIDTH * 2,   /* Enable + Status register */
     ACPI_FADT_OPTIONAL},

    {"Pm1aControlBlock",
     ACPI_FADT_OFFSET(xpm1a_control_block),
     ACPI_FADT_OFFSET(pm1a_control_block),
     ACPI_FADT_OFFSET(pm1_control_length),
     ACPI_PM1_REGISTER_WIDTH,
     ACPI_FADT_REQUIRED},

    {"Pm1bControlBlock",
     ACPI_FADT_OFFSET(xpm1b_control_block),
     ACPI_FADT_OFFSET(pm1b_control_block),
     ACPI_FADT_OFFSET(pm1_control_length),
     ACPI_PM1_REGISTER_WIDTH,
     ACPI_FADT_OPTIONAL},

    {"Pm2ControlBlock",
     ACPI_FADT_OFFSET(xpm2_control_block),
     ACPI_FADT_OFFSET(pm2_control_block),
     ACPI_FADT_OFFSET(pm2_control_length),
     ACPI_PM2_REGISTER_WIDTH,
     ACPI_FADT_SEPARATE_LENGTH},

    {"PmTimerBlock",
     ACPI_FADT_OFFSET(xpm_timer_block),
     ACPI_FADT_OFFSET(pm_timer_block),
     ACPI_FADT_OFFSET(pm_timer_length),
     ACPI_PM_TIMER_WIDTH,
     ACPI_FADT_REQUIRED},

    {"Gpe0Block",
     ACPI_FADT_OFFSET(xgpe0_block),
     ACPI_FADT_OFFSET(gpe0_block),
     ACPI_FADT_OFFSET(gpe0_block_length),
     0,
     ACPI_FADT_SEPARATE_LENGTH},

    {"Gpe1Block",
     ACPI_FADT_OFFSET(xgpe1_block),
     ACPI_FADT_OFFSET(gpe1_block),
     ACPI_FADT_OFFSET(gpe1_block_length),
     0,
     ACPI_FADT_SEPARATE_LENGTH}
};

#define ACPI_FADT_INFO_ENTRIES \
            (sizeof (fadt_info_table) / sizeof (struct acpi_fadt_info))

/* Table used to split Event Blocks into separate status/enable registers */

typedef struct acpi_fadt_pm_info {
    struct acpi_generic_address *target;
    u16 source;
    u8 register_num;

} acpi_fadt_pm_info;

static struct acpi_fadt_pm_info fadt_pm_info_table[] = {
    {&acpi_gbl_xpm1a_status,
     ACPI_FADT_OFFSET(xpm1a_event_block),
     0},

    {&acpi_gbl_xpm1a_enable,
     ACPI_FADT_OFFSET(xpm1a_event_block),
     1},

    {&acpi_gbl_xpm1b_status,
     ACPI_FADT_OFFSET(xpm1b_event_block),
     0},

    {&acpi_gbl_xpm1b_enable,
     ACPI_FADT_OFFSET(xpm1b_event_block),
     1}
};

#define ACPI_FADT_PM_INFO_ENTRIES \
            (sizeof (fadt_pm_info_table) / sizeof (struct acpi_fadt_pm_info))

/*******************************************************************************
 *
 * FUNCTION:    acpi_tb_init_generic_address
 *
 * PARAMETERS:  generic_address     - GAS struct to be initialized
 *              byte_width          - Width of this register
 *              address             - Address of the register
 *
 * RETURN:      None
 *
 * DESCRIPTION: Initialize a Generic Address Structure (GAS)
 *              See the ACPI specification for a full description and
 *              definition of this structure.
 *
 ******************************************************************************/

static void
acpi_tb_init_generic_address(struct acpi_generic_address *generic_address,
                 u8 space_id,
                 u8 byte_width, u64 address, char *register_name)
{
    u8 bit_width;

    /* Bit width field in the GAS is only one byte long, 255 max */

    bit_width = (u8)(byte_width * 8);

    if (byte_width > 31) {  /* (31*8)=248 */
        ACPI_ERROR((AE_INFO,
                "%s - 32-bit FADT register is too long (%u bytes, %u bits) "
                "to convert to GAS struct - 255 bits max, truncating",
                register_name, byte_width, (byte_width * 8)));

        bit_width = 255;
    }

    /*
     * The 64-bit Address field is non-aligned in the byte packed
     * GAS struct.
     */
    ACPI_MOVE_64_TO_64(&generic_address->address, &address);

    /* All other fields are byte-wide */

    generic_address->space_id = space_id;
    generic_address->bit_width = bit_width;
    generic_address->bit_offset = 0;
    generic_address->access_width = 0;  /* Access width ANY */
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_tb_parse_fadt
 *
 * PARAMETERS:  table_index         - Index for the FADT
 *
 * RETURN:      None
 *
 * DESCRIPTION: Initialize the FADT, DSDT and FACS tables
 *              (FADT contains the addresses of the DSDT and FACS)
 *
 ******************************************************************************/

void acpi_tb_parse_fadt(u32 table_index)
{
    u32 length;
    struct acpi_table_header *table;

    /*
     * The FADT has multiple versions with different lengths,
     * and it contains pointers to both the DSDT and FACS tables.
     *
     * Get a local copy of the FADT and convert it to a common format
     * Map entire FADT, assumed to be smaller than one page.
     */
    length = acpi_gbl_root_table_list.tables[table_index].length;

    table =
        acpi_os_map_memory(acpi_gbl_root_table_list.tables[table_index].
                   address, length);
    if (!table) {
        return;
    }

    /*
     * Validate the FADT checksum before we copy the table. Ignore
     * checksum error as we want to try to get the DSDT and FACS.
     */
    (void)acpi_tb_verify_checksum(table, length);

    /* Create a local copy of the FADT in common ACPI 2.0+ format */

    acpi_tb_create_local_fadt(table, length);

    /* All done with the real FADT, unmap it */

    acpi_os_unmap_memory(table, length);

    /* Obtain the DSDT and FACS tables via their addresses within the FADT */

    acpi_tb_install_table((acpi_physical_address) acpi_gbl_FADT.Xdsdt,
                  ACPI_SIG_DSDT, ACPI_TABLE_INDEX_DSDT);

    /* If Hardware Reduced flag is set, there is no FACS */

    if (!acpi_gbl_reduced_hardware) {
        acpi_tb_install_table((acpi_physical_address) acpi_gbl_FADT.
                      Xfacs, ACPI_SIG_FACS,
                      ACPI_TABLE_INDEX_FACS);
    }
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_tb_create_local_fadt
 *
 * PARAMETERS:  table               - Pointer to BIOS FADT
 *              length              - Length of the table
 *
 * RETURN:      None
 *
 * DESCRIPTION: Get a local copy of the FADT and convert it to a common format.
 *              Performs validation on some important FADT fields.
 *
 * NOTE:        We create a local copy of the FADT regardless of the version.
 *
 ******************************************************************************/

void acpi_tb_create_local_fadt(struct acpi_table_header *table, u32 length)
{
    /*
     * Check if the FADT is larger than the largest table that we expect
     * (the ACPI 5.0 version). If so, truncate the table, and issue
     * a warning.
     */
    if (length > sizeof(struct acpi_table_fadt)) {
        ACPI_BIOS_WARNING((AE_INFO,
                   "FADT (revision %u) is longer than ACPI 5.0 version, "
                   "truncating length %u to %u",
                   table->revision, length,
                   (u32)sizeof(struct acpi_table_fadt)));
    }

    /* Clear the entire local FADT */

    ACPI_MEMSET(&acpi_gbl_FADT, 0, sizeof(struct acpi_table_fadt));

    /* Copy the original FADT, up to sizeof (struct acpi_table_fadt) */

    ACPI_MEMCPY(&acpi_gbl_FADT, table,
            ACPI_MIN(length, sizeof(struct acpi_table_fadt)));

    /* Take a copy of the Hardware Reduced flag */

    acpi_gbl_reduced_hardware = FALSE;
    if (acpi_gbl_FADT.flags & ACPI_FADT_HW_REDUCED) {
        acpi_gbl_reduced_hardware = TRUE;
    }

    /* Convert the local copy of the FADT to the common internal format */

    acpi_tb_convert_fadt();

    /* Validate FADT values now, before we make any changes */

    acpi_tb_validate_fadt();

    /* Initialize the global ACPI register structures */

    acpi_tb_setup_fadt_registers();
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_tb_convert_fadt
 *
 * PARAMETERS:  None, uses acpi_gbl_FADT
 *
 * RETURN:      None
 *
 * DESCRIPTION: Converts all versions of the FADT to a common internal format.
 *              Expand 32-bit addresses to 64-bit as necessary.
 *
 * NOTE:        acpi_gbl_FADT must be of size (struct acpi_table_fadt),
 *              and must contain a copy of the actual FADT.
 *
 * Notes on 64-bit register addresses:
 *
 * After this FADT conversion, later ACPICA code will only use the 64-bit "X"
 * fields of the FADT for all ACPI register addresses.
 *
 * The 64-bit "X" fields are optional extensions to the original 32-bit FADT
 * V1.0 fields. Even if they are present in the FADT, they are optional and
 * are unused if the BIOS sets them to zero. Therefore, we must copy/expand
 * 32-bit V1.0 fields if the corresponding X field is zero.
 *
 * For ACPI 1.0 FADTs, all 32-bit address fields are expanded to the
 * corresponding "X" fields in the internal FADT.
 *
 * For ACPI 2.0+ FADTs, all valid (non-zero) 32-bit address fields are expanded
 * to the corresponding 64-bit X fields. For compatibility with other ACPI
 * implementations, we ignore the 64-bit field if the 32-bit field is valid,
 * regardless of whether the host OS is 32-bit or 64-bit.
 *
 ******************************************************************************/

static void acpi_tb_convert_fadt(void)
{
    struct acpi_generic_address *address64;
    u32 address32;
    u32 i;

    /*
     * Expand the 32-bit FACS and DSDT addresses to 64-bit as necessary.
     * Later code will always use the X 64-bit field. Also, check for an
     * address mismatch between the 32-bit and 64-bit address fields
     * (FIRMWARE_CTRL/X_FIRMWARE_CTRL, DSDT/X_DSDT) which would indicate
     * the presence of two FACS or two DSDT tables.
     */
    if (!acpi_gbl_FADT.Xfacs) {
        acpi_gbl_FADT.Xfacs = (u64) acpi_gbl_FADT.facs;
    } else if (acpi_gbl_FADT.facs &&
           (acpi_gbl_FADT.Xfacs != (u64) acpi_gbl_FADT.facs)) {
        ACPI_WARNING((AE_INFO,
            "32/64 FACS address mismatch in FADT - two FACS tables!"));
    }

    if (!acpi_gbl_FADT.Xdsdt) {
        acpi_gbl_FADT.Xdsdt = (u64) acpi_gbl_FADT.dsdt;
    } else if (acpi_gbl_FADT.dsdt &&
           (acpi_gbl_FADT.Xdsdt != (u64) acpi_gbl_FADT.dsdt)) {
        ACPI_WARNING((AE_INFO,
            "32/64 DSDT address mismatch in FADT - two DSDT tables!"));
    }

    /*
     * For ACPI 1.0 FADTs (revision 1 or 2), ensure that reserved fields which
     * should be zero are indeed zero. This will workaround BIOSs that
     * inadvertently place values in these fields.
     *
     * The ACPI 1.0 reserved fields that will be zeroed are the bytes located at
     * offset 45, 55, 95, and the word located at offset 109, 110.
     *
     * Note: The FADT revision value is unreliable. Only the length can be
     * trusted.
     */
    if (acpi_gbl_FADT.header.length <= ACPI_FADT_V2_SIZE) {
        acpi_gbl_FADT.preferred_profile = 0;
        acpi_gbl_FADT.pstate_control = 0;
        acpi_gbl_FADT.cst_control = 0;
        acpi_gbl_FADT.boot_flags = 0;
    }

    /* Update the local FADT table header length */

    acpi_gbl_FADT.header.length = sizeof(struct acpi_table_fadt);

    /*
     * Expand the ACPI 1.0 32-bit addresses to the ACPI 2.0 64-bit "X"
     * generic address structures as necessary. Later code will always use
     * the 64-bit address structures.
     *
     * March 2009:
     * We now always use the 32-bit address if it is valid (non-null). This
     * is not in accordance with the ACPI specification which states that
     * the 64-bit address supersedes the 32-bit version, but we do this for
     * compatibility with other ACPI implementations. Most notably, in the
     * case where both the 32 and 64 versions are non-null, we use the 32-bit
     * version. This is the only address that is guaranteed to have been
     * tested by the BIOS manufacturer.
     */
    for (i = 0; i < ACPI_FADT_INFO_ENTRIES; i++) {
        address32 = *ACPI_ADD_PTR(u32,
                      &acpi_gbl_FADT,
                      fadt_info_table[i].address32);

        address64 = ACPI_ADD_PTR(struct acpi_generic_address,
                     &acpi_gbl_FADT,
                     fadt_info_table[i].address64);

        /*
         * If both 32- and 64-bit addresses are valid (non-zero),
         * they must match.
         */
        if (address64->address && address32 &&
            (address64->address != (u64)address32)) {
            ACPI_BIOS_ERROR((AE_INFO,
                     "32/64X address mismatch in FADT/%s: "
                     "0x%8.8X/0x%8.8X%8.8X, using 32",
                     fadt_info_table[i].name, address32,
                     ACPI_FORMAT_UINT64(address64->
                                address)));
        }

        /* Always use 32-bit address if it is valid (non-null) */

        if (address32) {
            /*
             * Copy the 32-bit address to the 64-bit GAS structure. The
             * Space ID is always I/O for 32-bit legacy address fields
            */
            acpi_tb_init_generic_address(address64,
                             ACPI_ADR_SPACE_SYSTEM_IO,
                             *ACPI_ADD_PTR(u8,
                                   &acpi_gbl_FADT,
                                   fadt_info_table
                                   [i].length),
                             (u64) address32,
                             fadt_info_table[i].name);
        }
    }
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_tb_validate_fadt
 *
 * PARAMETERS:  table           - Pointer to the FADT to be validated
 *
 * RETURN:      None
 *
 * DESCRIPTION: Validate various important fields within the FADT. If a problem
 *              is found, issue a message, but no status is returned.
 *              Used by both the table manager and the disassembler.
 *
 * Possible additional checks:
 * (acpi_gbl_FADT.pm1_event_length >= 4)
 * (acpi_gbl_FADT.pm1_control_length >= 2)
 * (acpi_gbl_FADT.pm_timer_length >= 4)
 * Gpe block lengths must be multiple of 2
 *
 ******************************************************************************/

static void acpi_tb_validate_fadt(void)
{
    char *name;
    struct acpi_generic_address *address64;
    u8 length;
    u32 i;

    /*
     * Check for FACS and DSDT address mismatches. An address mismatch between
     * the 32-bit and 64-bit address fields (FIRMWARE_CTRL/X_FIRMWARE_CTRL and
     * DSDT/X_DSDT) would indicate the presence of two FACS or two DSDT tables.
     */
    if (acpi_gbl_FADT.facs &&
        (acpi_gbl_FADT.Xfacs != (u64)acpi_gbl_FADT.facs)) {
        ACPI_BIOS_WARNING((AE_INFO,
                   "32/64X FACS address mismatch in FADT - "
                   "0x%8.8X/0x%8.8X%8.8X, using 32",
                   acpi_gbl_FADT.facs,
                   ACPI_FORMAT_UINT64(acpi_gbl_FADT.Xfacs)));

        acpi_gbl_FADT.Xfacs = (u64)acpi_gbl_FADT.facs;
    }

    if (acpi_gbl_FADT.dsdt &&
        (acpi_gbl_FADT.Xdsdt != (u64)acpi_gbl_FADT.dsdt)) {
        ACPI_BIOS_WARNING((AE_INFO,
                   "32/64X DSDT address mismatch in FADT - "
                   "0x%8.8X/0x%8.8X%8.8X, using 32",
                   acpi_gbl_FADT.dsdt,
                   ACPI_FORMAT_UINT64(acpi_gbl_FADT.Xdsdt)));

        acpi_gbl_FADT.Xdsdt = (u64)acpi_gbl_FADT.dsdt;
    }

    /* If Hardware Reduced flag is set, we are all done */

    if (acpi_gbl_reduced_hardware) {
        return;
    }

    /* Examine all of the 64-bit extended address fields (X fields) */

    for (i = 0; i < ACPI_FADT_INFO_ENTRIES; i++) {
        /*
         * Generate pointer to the 64-bit address, get the register
         * length (width) and the register name
         */
        address64 = ACPI_ADD_PTR(struct acpi_generic_address,
                     &acpi_gbl_FADT,
                     fadt_info_table[i].address64);
        length =
            *ACPI_ADD_PTR(u8, &acpi_gbl_FADT,
                  fadt_info_table[i].length);
        name = fadt_info_table[i].name;

        /*
         * For each extended field, check for length mismatch between the
         * legacy length field and the corresponding 64-bit X length field.
         */
        if (address64->address &&
            (address64->bit_width != ACPI_MUL_8(length))) {
            ACPI_BIOS_WARNING((AE_INFO,
                       "32/64X length mismatch in FADT/%s: %u/%u",
                       name, ACPI_MUL_8(length),
                       address64->bit_width));
        }

        if (fadt_info_table[i].type & ACPI_FADT_REQUIRED) {
            /*
             * Field is required (Pm1a_event, Pm1a_control, pm_timer).
             * Both the address and length must be non-zero.
             */
            if (!address64->address || !length) {
                ACPI_BIOS_ERROR((AE_INFO,
                         "Required FADT field %s has zero address and/or length: "
                         "0x%8.8X%8.8X/0x%X",
                         name,
                         ACPI_FORMAT_UINT64(address64->
                                    address),
                         length));
            }
        } else if (fadt_info_table[i].type & ACPI_FADT_SEPARATE_LENGTH) {
            /*
             * Field is optional (Pm2_control, GPE0, GPE1) AND has its own
             * length field. If present, both the address and length must
             * be valid.
             */
            if ((address64->address && !length) ||
                (!address64->address && length)) {
                ACPI_BIOS_WARNING((AE_INFO,
                           "Optional FADT field %s has zero address or length: "
                           "0x%8.8X%8.8X/0x%X",
                           name,
                           ACPI_FORMAT_UINT64
                           (address64->address),
                           length));
            }
        }
    }
}

/*******************************************************************************
 *
 * FUNCTION:    acpi_tb_setup_fadt_registers
 *
 * PARAMETERS:  None, uses acpi_gbl_FADT.
 *
 * RETURN:      None
 *
 * DESCRIPTION: Initialize global ACPI PM1 register definitions. Optionally,
 *              force FADT register definitions to their default lengths.
 *
 ******************************************************************************/

static void acpi_tb_setup_fadt_registers(void)
{
    struct acpi_generic_address *target64;
    struct acpi_generic_address *source64;
    u8 pm1_register_byte_width;
    u32 i;

    /*
     * Optionally check all register lengths against the default values and
     * update them if they are incorrect.
     */
    if (acpi_gbl_use_default_register_widths) {
        for (i = 0; i < ACPI_FADT_INFO_ENTRIES; i++) {
            target64 =
                ACPI_ADD_PTR(struct acpi_generic_address,
                     &acpi_gbl_FADT,
                     fadt_info_table[i].address64);

            /*
             * If a valid register (Address != 0) and the (default_length > 0)
             * (Not a GPE register), then check the width against the default.
             */
            if ((target64->address) &&
                (fadt_info_table[i].default_length > 0) &&
                (fadt_info_table[i].default_length !=
                 target64->bit_width)) {
                ACPI_BIOS_WARNING((AE_INFO,
                           "Invalid length for FADT/%s: %u, using default %u",
                           fadt_info_table[i].name,
                           target64->bit_width,
                           fadt_info_table[i].
                           default_length));

                /* Incorrect size, set width to the default */

                target64->bit_width =
                    fadt_info_table[i].default_length;
            }
        }
    }

    /*
     * Get the length of the individual PM1 registers (enable and status).
     * Each register is defined to be (event block length / 2). Extra divide
     * by 8 converts bits to bytes.
     */
    pm1_register_byte_width = (u8)
        ACPI_DIV_16(acpi_gbl_FADT.xpm1a_event_block.bit_width);

    /*
     * Calculate separate GAS structs for the PM1x (A/B) Status and Enable
     * registers. These addresses do not appear (directly) in the FADT, so it
     * is useful to pre-calculate them from the PM1 Event Block definitions.
     *
     * The PM event blocks are split into two register blocks, first is the
     * PM Status Register block, followed immediately by the PM Enable
     * Register block. Each is of length (pm1_event_length/2)
     *
     * Note: The PM1A event block is required by the ACPI specification.
     * However, the PM1B event block is optional and is rarely, if ever,
     * used.
     */

    for (i = 0; i < ACPI_FADT_PM_INFO_ENTRIES; i++) {
        source64 =
            ACPI_ADD_PTR(struct acpi_generic_address, &acpi_gbl_FADT,
                 fadt_pm_info_table[i].source);

        if (source64->address) {
            acpi_tb_init_generic_address(fadt_pm_info_table[i].
                             target, source64->space_id,
                             pm1_register_byte_width,
                             source64->address +
                             (fadt_pm_info_table[i].
                              register_num *
                              pm1_register_byte_width),
                             "PmRegisters");
        }
    }
}