1 files changed, 26 insertions, 18 deletions

diff --git a/drivers/acpi/tables/tbfadt.c b/drivers/acpi/tables/tbfadt.c
index 1285e91474fb..002bb33003af 100644
--- a/drivers/acpi/tables/tbfadt.c
+++ b/drivers/acpi/tables/tbfadt.c
@@ -211,14 +211,17 @@ void acpi_tb_parse_fadt(acpi_native_uint table_index, u8 flags)
  * DESCRIPTION: Get a local copy of the FADT and convert it to a common format.
  *              Performs validation on some important FADT fields.
  *
+ * NOTE:        We create a local copy of the FADT regardless of the version.
+ *
  ******************************************************************************/
 
 void acpi_tb_create_local_fadt(struct acpi_table_header *table, u32 length)
 {
 
         /*
-         * Check if the FADT is larger than what we know about (ACPI 2.0 version).
-         * Truncate the table, but make some noise.
+         * Check if the FADT is larger than the largest table that we expect
+         * (the ACPI 2.0/3.0 version). If so, truncate the table, and issue
+         * a warning.
          */
         if (length > sizeof(struct acpi_table_fadt)) {
                 ACPI_WARNING((AE_INFO,
@@ -227,10 +230,12 @@ void acpi_tb_create_local_fadt(struct acpi_table_header *table, u32 length)
                               sizeof(struct acpi_table_fadt)));
         }
 
-        /* Copy the entire FADT locally. Zero first for tb_convert_fadt */
+        /* Clear the entire local FADT */
 
         ACPI_MEMSET(&acpi_gbl_FADT, 0, sizeof(struct acpi_table_fadt));
 
+        /* Copy the original FADT, up to sizeof (struct acpi_table_fadt) */
+
         ACPI_MEMCPY(&acpi_gbl_FADT, table,
                     ACPI_MIN(length, sizeof(struct acpi_table_fadt)));
 
@@ -251,7 +256,7 @@ void acpi_tb_create_local_fadt(struct acpi_table_header *table, u32 length)
  * RETURN:      None
  *
  * DESCRIPTION: Converts all versions of the FADT to a common internal format.
- *              -> Expand all 32-bit addresses to 64-bit.
+ *              Expand all 32-bit addresses to 64-bit.
  *
  * NOTE:        acpi_gbl_FADT must be of size (struct acpi_table_fadt),
  *              and must contain a copy of the actual FADT.
@@ -292,8 +297,23 @@ static void acpi_tb_convert_fadt(void)
         }
 
         /*
-         * Expand the 32-bit V1.0 addresses to the 64-bit "X" generic address
-         * structures as necessary.
+         * For ACPI 1.0 FADTs (revision 1 or 2), ensure that reserved fields which
+         * should be zero are indeed zero. This will workaround BIOSs that
+         * inadvertently place values in these fields.
+         *
+         * The ACPI 1.0 reserved fields that will be zeroed are the bytes located at
+         * offset 45, 55, 95, and the word located at offset 109, 110.
+         */
+        if (acpi_gbl_FADT.header.revision < 3) {
+                acpi_gbl_FADT.preferred_profile = 0;
+                acpi_gbl_FADT.pstate_control = 0;
+                acpi_gbl_FADT.cst_control = 0;
+                acpi_gbl_FADT.boot_flags = 0;
+        }
+
+        /*
+         * Expand the ACPI 1.0 32-bit V1.0 addresses to the ACPI 2.0 64-bit "X"
+         * generic address structures as necessary.
          */
         for (i = 0; i < ACPI_FADT_INFO_ENTRIES; i++) {
                 target =
@@ -349,18 +369,6 @@ static void acpi_tb_convert_fadt(void)
                     acpi_gbl_FADT.xpm1a_event_block.space_id;
 
         }
-
-        /*
-         * For ACPI 1.0 FADTs, ensure that reserved fields (which should be zero)
-         * are indeed zero. This will workaround BIOSs that inadvertently placed
-         * values in these fields.
-         */
-        if (acpi_gbl_FADT.header.revision < 3) {
-                acpi_gbl_FADT.preferred_profile = 0;
-                acpi_gbl_FADT.pstate_control = 0;
-                acpi_gbl_FADT.cst_control = 0;
-                acpi_gbl_FADT.boot_flags = 0;
-        }
 }
 
 /******************************************************************************