[PATCH] ACPI: Fix 2.6.21 boot regression on P4/HT

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>

diff --git a/drivers/acpi/tables/tbfadt.c b/drivers/acpi/tables/tbfadt.c
index 807c7116e94b8eaa19471ce66ab4196e0ef66c06..d34149140d8683113462095c4fc01e1ef0189061 100644 (file)
--- a/drivers/acpi/tables/tbfadt.c
+++ b/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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