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Subject[patch 04/69] ACPI: Fix 2.6.21 boot regression on P4/HT
-stable review patch.  If anyone has any objections, please let us know.
---------------------

From: Len Brown <lenb@kernel.org>

Up through 2.6.20 we cleared the FADT.CSTATE_CONTROL field
for FADT versions before r3, because it made no sense
for that reserved field to be set for pre-ACPI 2.0 systems.

It turns out that not clearing this field exposes
Linux to SMM BIOS failures, so do the same in 2.6.21.

http://bugzilla.kernel.org/show_bug.cgi?id=8346

Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
---
drivers/acpi/tables/tbfadt.c | 14 ++++++++++++++
1 file changed, 14 insertions(+)

--- linux-2.6.21.1.orig/drivers/acpi/tables/tbfadt.c
+++ linux-2.6.21.1/drivers/acpi/tables/tbfadt.c
@@ -347,6 +347,20 @@ static void acpi_tb_convert_fadt(void)
acpi_gbl_xpm1b_enable.space_id = acpi_gbl_FADT.xpm1a_event_block.space_id;

}
+ /*
+ * _CST object and C States change notification start with
+ * ACPI 2.0 (FADT r3). Although the field should be Reserved
+ * and 0 before then, some pre-r3 FADT set this field and
+ * it results in SMM-related boot failures. For them, clear it.
+ */
+ if ((acpi_gbl_FADT.header.revision < 3) &&
+ (acpi_gbl_FADT.cst_control != 0)) {
+ ACPI_WARNING((AE_INFO,
+ "Ignoring BIOS FADT r%u C-state control",
+ acpi_gbl_FADT.header.revision));
+ acpi_gbl_FADT.cst_control = 0;
+ }
+
}

/******************************************************************************
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