ACPI : Use RSDT instead of XSDT by adding boot option of "acpi=rsdt"

On some boxes there exist both RSDT and XSDT table. But unfortunately
sometimes there exists the following error when XSDT table is used:
   a. 32/64X address mismatch
   b. The 32/64X FACS address mismatch

   In such case the boot option of "acpi=rsdt" is provided so that
RSDT is tried instead of XSDT table when the system can't work well.

http://bugzilla.kernel.org/show_bug.cgi?id=8246

Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
cc:Thomas Renninger <trenn@suse.de>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index c9115c1b672c..136f02842de9 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -139,6 +139,7 @@ and is between 256 and 4096 characters. It is defined in the file
                         ht -- run only enough ACPI to enable Hyper Threading
                         strict -- Be less tolerant of platforms that are not
                                 strictly ACPI specification compliant.
+                        rsdt -- prefer RSDT over (default) XSDT
 
                         See also Documentation/power/pm.txt, pci=noacpi