1 files changed, 62 insertions, 15 deletions

diff --git a/drivers/acpi/hardware/hwregs.c b/drivers/acpi/hardware/hwregs.c
index ae142de19507..3143f36fcec9 100644
--- a/drivers/acpi/hardware/hwregs.c
+++ b/drivers/acpi/hardware/hwregs.c
@@ -172,9 +172,9 @@ acpi_get_sleep_type_data(u8 sleep_state, u8 * sleep_type_a, u8 * sleep_type_b)
         }
 
         /*
-         * The package must have at least two elements.  NOTE (March 2005): This
+         * The package must have at least two elements. NOTE (March 2005): This
          * goes against the current ACPI spec which defines this object as a
-         * package with one encoded DWORD element.  However, existing practice
+         * package with one encoded DWORD element. However, existing practice
          * by BIOS vendors seems to be to have 2 or more elements, at least
          * one per sleep type (A/B).
          */
@@ -255,7 +255,7 @@ struct acpi_bit_register_info *acpi_hw_get_bit_register_info(u32 register_id)
  *              return_value    - Value that was read from the register
  *              Flags           - Lock the hardware or not
  *
- * RETURN:      Status and the value read from specified Register.  Value
+ * RETURN:      Status and the value read from specified Register. Value
  *              returned is normalized to bit0 (is shifted all the way right)
  *
  * DESCRIPTION: ACPI bit_register read function.
@@ -361,8 +361,8 @@ acpi_status acpi_set_register(u32 register_id, u32 value, u32 flags)
         case ACPI_REGISTER_PM1_STATUS:
 
                 /*
-                 * Status Registers are different from the rest.  Clear by
-                 * writing 1, and writing 0 has no effect.  So, the only relevant
+                 * Status Registers are different from the rest. Clear by
+                 * writing 1, and writing 0 has no effect. So, the only relevant
                  * information is the single bit we're interested in, all others should
                  * be written as 0 so they will be left unchanged.
                  */
@@ -467,14 +467,13 @@ ACPI_EXPORT_SYMBOL(acpi_set_register)
  *
  * FUNCTION:    acpi_hw_register_read
  *
- * PARAMETERS:  use_lock            - Mutex hw access
- *              register_id         - register_iD + Offset
+ * PARAMETERS:  use_lock            - Lock hardware? True/False
+ *              register_id         - ACPI Register ID
  *              return_value        - Where the register value is returned
  *
  * RETURN:      Status and the value read.
  *
- * DESCRIPTION: Acpi register read function.  Registers are read at the
- *              given offset.
+ * DESCRIPTION: Read from the specified ACPI register
  *
  ******************************************************************************/
 acpi_status
@@ -580,14 +579,26 @@ acpi_hw_register_read(u8 use_lock, u32 register_id, u32 * return_value)
  *
  * FUNCTION:    acpi_hw_register_write
  *
- * PARAMETERS:  use_lock            - Mutex hw access
- *              register_id         - register_iD + Offset
+ * PARAMETERS:  use_lock            - Lock hardware? True/False
+ *              register_id         - ACPI Register ID
  *              Value               - The value to write
  *
  * RETURN:      Status
  *
- * DESCRIPTION: Acpi register Write function.  Registers are written at the
- *              given offset.
+ * DESCRIPTION: Write to the specified ACPI register
+ *
+ * NOTE: In accordance with the ACPI specification, this function automatically
+ * preserves the value of the following bits, meaning that these bits cannot be
+ * changed via this interface:
+ *
+ * PM1_CONTROL[0] = SCI_EN
+ * PM1_CONTROL[9]
+ * PM1_STATUS[11]
+ *
+ * ACPI References:
+ * 1) Hardware Ignored Bits: When software writes to a register with ignored
+ *      bit fields, it preserves the ignored bit fields
+ * 2) SCI_EN: OSPM always preserves this bit position
  *
  ******************************************************************************/
 
@@ -595,6 +606,7 @@ acpi_status acpi_hw_register_write(u8 use_lock, u32 register_id, u32 value)
 {
         acpi_status status;
         acpi_cpu_flags lock_flags = 0;
+        u32 read_value;
 
         ACPI_FUNCTION_TRACE(hw_register_write);
 
@@ -605,6 +617,22 @@ acpi_status acpi_hw_register_write(u8 use_lock, u32 register_id, u32 value)
         switch (register_id) {
         case ACPI_REGISTER_PM1_STATUS:  /* 16-bit access */
 
+                /* Perform a read first to preserve certain bits (per ACPI spec) */
+
+                status = acpi_hw_register_read(ACPI_MTX_DO_NOT_LOCK,
+                                               ACPI_REGISTER_PM1_STATUS,
+                                               &read_value);
+                if (ACPI_FAILURE(status)) {
+                        goto unlock_and_exit;
+                }
+
+                /* Insert the bits to be preserved */
+
+                ACPI_INSERT_BITS(value, ACPI_PM1_STATUS_PRESERVED_BITS,
+                                 read_value);
+
+                /* Now we can write the data */
+
                 status =
                     acpi_hw_low_level_write(16, value,
                                             &acpi_gbl_FADT->xpm1a_evt_blk);
@@ -635,6 +663,25 @@ acpi_status acpi_hw_register_write(u8 use_lock, u32 register_id, u32 value)
 
         case ACPI_REGISTER_PM1_CONTROL: /* 16-bit access */
 
+                /*
+                 * Perform a read first to preserve certain bits (per ACPI spec)
+                 *
+                 * Note: This includes SCI_EN, we never want to change this bit
+                 */
+                status = acpi_hw_register_read(ACPI_MTX_DO_NOT_LOCK,
+                                               ACPI_REGISTER_PM1_CONTROL,
+                                               &read_value);
+                if (ACPI_FAILURE(status)) {
+                        goto unlock_and_exit;
+                }
+
+                /* Insert the bits to be preserved */
+
+                ACPI_INSERT_BITS(value, ACPI_PM1_CONTROL_PRESERVED_BITS,
+                                 read_value);
+
+                /* Now we can write the data */
+
                 status =
                     acpi_hw_low_level_write(16, value,
                                             &acpi_gbl_FADT->xpm1a_cnt_blk);
@@ -726,7 +773,7 @@ acpi_hw_low_level_read(u32 width, u32 * value, struct acpi_generic_address *reg)
                 return (AE_OK);
         }
 
-        /* Get a local copy of the address.  Handles possible alignment issues */
+        /* Get a local copy of the address. Handles possible alignment issues */
 
         ACPI_MOVE_64_TO_64(&address, &reg->address);
         if (!address) {
@@ -798,7 +845,7 @@ acpi_hw_low_level_write(u32 width, u32 value, struct acpi_generic_address * reg)
                 return (AE_OK);
         }
 
-        /* Get a local copy of the address.  Handles possible alignment issues */
+        /* Get a local copy of the address. Handles possible alignment issues */
 
         ACPI_MOVE_64_TO_64(&address, &reg->address);
         if (!address) {