ACPICA: Hardcode access width for the reset register.

The ACPI spec requires the reset register width to be 8, so we
now hardcode it and ignore the FADT value. This provides/maintains
compatibility with other ACPI implementations that have allowed
BIOS code with bad register width values to go unnoticed.
Matthew Garett, Bob Moore, Lv Zheng.
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/acpica/hwxface.c

@@ -83,11 +83,17 @@ acpi_status acpi_reset(void)
 		 * For I/O space, write directly to the OSL. This bypasses the port
 		 * validation mechanism, which may block a valid write to the reset
 		 * register.
-		 * Spec section 4.7.3.6 requires register width to be 8.
+		 *
+		 * NOTE:
+		 * The ACPI spec requires the reset register width to be 8, so we
+		 * hardcode it here and ignore the FADT value. This maintains
+		 * compatibility with other ACPI implementations that have allowed
+		 * BIOS code with bad register width values to go unnoticed.
 		 */
 		status =
 		    acpi_os_write_port((acpi_io_address) reset_reg->address,
-				       acpi_gbl_FADT.reset_value, 8);
+				       acpi_gbl_FADT.reset_value,
+				       ACPI_RESET_REGISTER_WIDTH);
 	} else {
 		/* Write the reset value to the reset register */
 

include/acpi/actypes.h

@@ -349,6 +349,7 @@ typedef u32 acpi_physical_address;
 #define ACPI_PM1_REGISTER_WIDTH         16
 #define ACPI_PM2_REGISTER_WIDTH         8
 #define ACPI_PM_TIMER_WIDTH             32
+#define ACPI_RESET_REGISTER_WIDTH       8
 
 /* Names within the namespace are 4 bytes long */