ACPICA: Cleanup the option of forcing the use of the RSDT.

This change adds a runtime option that will force ACPICA to use the
RSDT instead of the XSDT. Although the ACPI spec requires that an XSDT
be used instead of the RSDT, the XSDT has been found to be corrupt or
ill-formed on some machines.

This option is already in the Linux kernel.  When it is back ported to
ACPICA, code is re-written to follow ACPICA coding style.  This patch
is the generation of the integration.

Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

2 files changed, 13 insertions, 5 deletions

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);