ACPICA: Clear PM register write-only bits on reading
Affects PM1 Control register only. When reading the register, zero
the write-only bits as per the ACPI spec. ACPICA BZ 443. Lin Ming.
http://www.acpica.org/bugzilla/show_bug.cgi?id=443
Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/drivers/acpi/acpica/hwregs.c b/drivers/acpi/acpica/hwregs.c
index f8ee0a7..7b2fb60 100644
--- a/drivers/acpi/acpica/hwregs.c
+++ b/drivers/acpi/acpica/hwregs.c
@@ -207,6 +207,13 @@
xpm1a_control_block,
&acpi_gbl_FADT.
xpm1b_control_block);
+
+ /*
+ * Zero the write-only bits. From the ACPI specification, "Hardware
+ * Write-Only Bits": "Upon reads to registers with write-only bits,
+ * software masks out all write-only bits."
+ */
+ value &= ~ACPI_PM1_CONTROL_WRITEONLY_BITS;
break;
case ACPI_REGISTER_PM2_CONTROL: /* 8-bit access */