2 files changed, 24 insertions, 1 deletions

diff --git a/drivers/acpi/acpica/aclocal.h b/drivers/acpi/acpica/aclocal.h
index 18a8d96eaa49..f01e155b2bcc 100644
--- a/drivers/acpi/acpica/aclocal.h
+++ b/drivers/acpi/acpica/aclocal.h
@@ -780,7 +780,15 @@ struct acpi_bit_register_info {
  * must be preserved.
  */
 #define ACPI_PM1_STATUS_PRESERVED_BITS          0x0800  /* Bit 11 */
-#define ACPI_PM1_CONTROL_PRESERVED_BITS         0x0200  /* Bit 9 (whatever) */
+
+/* For control registers, both ignored and reserved bits must be preserved */
+
+#define ACPI_PM1_CONTROL_IGNORED_BITS           0x0201  /* Bits 9, 0(SCI_EN) */
+#define ACPI_PM1_CONTROL_RESERVED_BITS          0xC1F8  /* Bits 14-15, 3-8 */
+#define ACPI_PM1_CONTROL_PRESERVED_BITS \
+               (ACPI_PM1_CONTROL_IGNORED_BITS | ACPI_PM1_CONTROL_RESERVED_BITS)
+
+#define ACPI_PM2_CONTROL_PRESERVED_BITS         0xFFFFFFFE      /* All except bit 0 */
 
 /*
  * Register IDs
diff --git a/drivers/acpi/acpica/hwregs.c b/drivers/acpi/acpica/hwregs.c
index fd7abe277db3..611736266f9f 100644
--- a/drivers/acpi/acpica/hwregs.c
+++ b/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;