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ACPI: Ingore the RESET_REG_SUP bit when using ACPI reset mechanism

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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>
This commit is contained in:
Zhao Yakui 2008-10-17 14:22:27 -04:00 committed by Len Brown
parent 3fa8749e58
commit 8fd145917f
1 changed files with 22 additions and 3 deletions
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25
drivers/acpi/reboot.c
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@ -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;