5 files changed, 22 insertions, 16 deletions

diff --git a/arch/ia64/kernel/acpi.c b/arch/ia64/kernel/acpi.c
index 59d52e3aef12..28dc6ba6690a 100644
--- a/arch/ia64/kernel/acpi.c
+++ b/arch/ia64/kernel/acpi.c
@@ -61,7 +61,6 @@
 
 #define PREFIX                  "ACPI: "
 
-u32 acpi_rsdt_forced;
 unsigned int acpi_cpei_override;
 unsigned int acpi_cpei_phys_cpuid;
 
diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 6c0b43bd024b..0b0b91b83d51 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -46,7 +46,6 @@
 
 #include "sleep.h" /* To include x86_acpi_suspend_lowlevel */
 static int __initdata acpi_force = 0;
-u32 acpi_rsdt_forced;
 int acpi_disabled;
 EXPORT_SYMBOL(acpi_disabled);
 
@@ -1564,7 +1563,7 @@ static int __init parse_acpi(char *arg)
         }
         /* acpi=rsdt use RSDT instead of XSDT */
         else if (strcmp(arg, "rsdt") == 0) {
-                acpi_rsdt_forced = 1;
+                acpi_gbl_do_not_use_xsdt = TRUE;
         }
         /* "acpi=noirq" disables ACPI interrupt routing */
         else if (strcmp(arg, "noirq") == 0) {
diff --git a/drivers/acpi/acpica/acglobal.h b/drivers/acpi/acpica/acglobal.h
index e9f1fc7f99c7..cffb45742aa5 100644
--- a/drivers/acpi/acpica/acglobal.h
+++ b/drivers/acpi/acpica/acglobal.h
@@ -119,6 +119,14 @@ bool ACPI_INIT_GLOBAL(acpi_gbl_enable_aml_debug_object, FALSE);
 u8 ACPI_INIT_GLOBAL(acpi_gbl_copy_dsdt_locally, FALSE);
 
 /*
+ * Optionally ignore an XSDT if present and use the RSDT instead.
+ * Although the ACPI specification requires that an XSDT be used instead
+ * of the RSDT, the XSDT has been found to be corrupt or ill-formed on
+ * some machines. Default behavior is to use the XSDT if present.
+ */
+u8 ACPI_INIT_GLOBAL(acpi_gbl_do_not_use_xsdt, FALSE);
+
+/*
  * Optionally truncate I/O addresses to 16 bits. Provides compatibility
  * with other ACPI implementations. NOTE: During ACPICA initialization,
  * this value is set to TRUE if any Windows OSI strings have been
diff --git a/drivers/acpi/acpica/tbutils.c b/drivers/acpi/acpica/tbutils.c
index ee6067062cdc..6412d3c301cb 100644
--- a/drivers/acpi/acpica/tbutils.c
+++ b/drivers/acpi/acpica/tbutils.c
@@ -478,10 +478,10 @@ acpi_status __init acpi_tb_parse_root_table(acpi_physical_address rsdp_address)
                                    ACPI_CAST_PTR(struct acpi_table_header,
                                                  rsdp));
 
-        /* Differentiate between RSDT and XSDT root tables */
+        /* Use XSDT if present and not overridden. Otherwise, use RSDT */
 
-        if ((rsdp->revision > 1) && rsdp->xsdt_physical_address
-                        && !acpi_rsdt_forced) {
+        if ((rsdp->revision > 1) &&
+            rsdp->xsdt_physical_address && !acpi_gbl_do_not_use_xsdt) {
                 /*
                  * RSDP contains an XSDT (64-bit physical addresses). We must use
                  * the XSDT if the revision is > 1 and the XSDT pointer is present,
@@ -503,8 +503,8 @@ acpi_status __init acpi_tb_parse_root_table(acpi_physical_address rsdp_address)
         acpi_os_unmap_memory(rsdp, sizeof(struct acpi_table_rsdp));
 
         /*
-         * If it is present, validate the XSDT for access/size and ensure
-         * that all table entries are at least non-NULL
+         * If it is present and used, validate the XSDT for access/size
+         * and ensure that all table entries are at least non-NULL
          */
         if (table_entry_size == ACPI_XSDT_ENTRY_SIZE) {
                 status = acpi_tb_validate_xsdt(address);
diff --git a/include/acpi/acpixf.h b/include/acpi/acpixf.h
index 4278aba96503..30b01f889538 100644
--- a/include/acpi/acpixf.h
+++ b/include/acpi/acpixf.h
@@ -54,7 +54,6 @@
 #include <acpi/acbuffer.h>
 
 extern u8 acpi_gbl_permanent_mmap;
-extern u32 acpi_rsdt_forced;
 
 /*
  * Globals that are publically available
@@ -72,17 +71,18 @@ extern u32 acpi_dbg_layer;
 
 /* ACPICA runtime options */
 
-extern u8 acpi_gbl_enable_interpreter_slack;
 extern u8 acpi_gbl_all_methods_serialized;
-extern u8 acpi_gbl_create_osi_method;
-extern u8 acpi_gbl_use_default_register_widths;
-extern acpi_name acpi_gbl_trace_method_name;
-extern u32 acpi_gbl_trace_flags;
-extern bool acpi_gbl_enable_aml_debug_object;
 extern u8 acpi_gbl_copy_dsdt_locally;
-extern u8 acpi_gbl_truncate_io_addresses;
+extern u8 acpi_gbl_create_osi_method;
 extern u8 acpi_gbl_disable_auto_repair;
 extern u8 acpi_gbl_disable_ssdt_table_load;
+extern u8 acpi_gbl_do_not_use_xsdt;
+extern bool acpi_gbl_enable_aml_debug_object;
+extern u8 acpi_gbl_enable_interpreter_slack;
+extern u32 acpi_gbl_trace_flags;
+extern acpi_name acpi_gbl_trace_method_name;
+extern u8 acpi_gbl_truncate_io_addresses;
+extern u8 acpi_gbl_use_default_register_widths;
 
 /*
  * Hardware-reduced prototypes. All interfaces that use these macros will