ACPICA: Preserve all PM control reserved and ignored bits

As per the ACPI specification, preserve (read/modify/write) all
bits that are defined as either reserved or ignored (PM control
control registers only.)

Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/acpi/acpica/hwregs.c

@@ -328,6 +328,21 @@ acpi_status acpi_hw_register_write(u32 register_id, u32 value)
 
 	case ACPI_REGISTER_PM2_CONTROL:	/* 8-bit access */
 
+		/*
+		 * For control registers, all reserved bits must be preserved,
+		 * as per the ACPI spec.
+		 */
+		status =
+		    acpi_read(&read_value, &acpi_gbl_FADT.xpm2_control_block);
+		if (ACPI_FAILURE(status)) {
+			goto exit;
+		}
+
+		/* Insert the bits to be preserved */
+
+		ACPI_INSERT_BITS(value, ACPI_PM2_CONTROL_PRESERVED_BITS,
+				 read_value);
+
 		status = acpi_write(value, &acpi_gbl_FADT.xpm2_control_block);
 		break;