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    Subject[patch 51/57] ACPI: Ingore the RESET_REG_SUP bit when using ACPI reset mechanism
    2.6.27-stable review patch.  If anyone has any objections, please let us know.

    ------------------
    From: Zhao Yakui <yakui.zhao@intel.com>

    Subject: [patch 51/57] ACPI: Ingore the RESET_REG_SUP bit when using ACPI reset mechanism

    commit 8fd145917fb62368a9b80db59562c20576238f5a upstream

    ACPI: Ingore the RESET_REG_SUP bit when using ACPI reset mechanism

    According to ACPI 3.0, FADT.flags.RESET_REG_SUP indicates
    whether the ACPI reboot mechanism is supported.

    However, some boxes have this bit clear, have a valid
    ACPI_RESET_REG & RESET_VALUE, and ACPI reboot is the only
    mechanism that works for them after S3.

    This suggests that other operating systems may not be checking
    the RESET_REG_SUP bit, and are using other means to decide
    whether to use the ACPI reboot mechanism or not.

    Here we stop checking RESET_REG_SUP.
    Instead, When acpi reboot is requested,
    only the reset_register is checked. If the following
    conditions are met, it indicates that the reset register is supported.
    a. reset_register is not zero
    b. the access width is eight
    c. the bit_offset is zero

    http://bugzilla.kernel.org/show_bug.cgi?id=7299
    http://bugzilla.kernel.org/show_bug.cgi?id=1148

    Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
    Signed-off-by: Len Brown <len.brown@intel.com>
    Cc: Chuck Ebbert <cebbert@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

    ---
    drivers/acpi/reboot.c | 25 ++++++++++++++++++++++---
    1 file changed, 22 insertions(+), 3 deletions(-)

    --- a/drivers/acpi/reboot.c
    +++ b/drivers/acpi/reboot.c
    @@ -15,9 +15,28 @@ void acpi_reboot(void)

    rr = &acpi_gbl_FADT.reset_register;

    - /* Is the reset register supported? */
    - if (!(acpi_gbl_FADT.flags & ACPI_FADT_RESET_REGISTER) ||
    - rr->bit_width != 8 || rr->bit_offset != 0)
    + /*
    + * Is the ACPI reset register supported?
    + *
    + * According to ACPI 3.0, FADT.flags.RESET_REG_SUP indicates
    + * whether the ACPI reset mechanism is supported.
    + *
    + * However, some boxes have this bit clear, yet a valid
    + * ACPI_RESET_REG & RESET_VALUE, and ACPI reboot is the only
    + * mechanism that works for them after S3.
    + *
    + * This suggests that other operating systems may not be checking
    + * the RESET_REG_SUP bit, and are using other means to decide
    + * whether to use the ACPI reboot mechanism or not.
    + *
    + * So when acpi reboot is requested,
    + * only the reset_register is checked. If the following
    + * conditions are met, it indicates that the reset register is supported.
    + * a. reset_register is not zero
    + * b. the access width is eight
    + * c. the bit_offset is zero
    + */
    + if (!(rr->address) || rr->bit_width != 8 || rr->bit_offset != 0)
    return;

    reset_value = acpi_gbl_FADT.reset_value;
    --


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