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, 2 insertions, 1 deletions

diff --git a/drivers/acpi/tables/tbutils.c b/drivers/acpi/tables/tbutils.c
index 0cc92ef5236f..da9f240186e8 100644
--- a/drivers/acpi/tables/tbutils.c
+++ b/drivers/acpi/tables/tbutils.c
@@ -420,7 +420,8 @@ acpi_tb_parse_root_table(acpi_physical_address rsdp_address, u8 flags)
 
         /* Differentiate between RSDT and XSDT root tables */
 
-        if (rsdp->revision > 1 && rsdp->xsdt_physical_address) {
+        if (rsdp->revision > 1 && rsdp->xsdt_physical_address
+                        && !acpi_rsdt_forced) {
                 /*
                  * Root table is an XSDT (64-bit physical addresses). We must use the
                  * XSDT if the revision is > 1 and the XSDT pointer is present, as per