ACPICA: Truncate I/O addresses to 16 bits for Windows compatibility

This feature is optional and is enabled if the BIOS requests any
Windows OSI strings. It can also be enabled by the host OS.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
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>

3 files changed, 29 insertions, 0 deletions

diff --git a/drivers/acpi/acpica/acglobal.h b/drivers/acpi/acpica/acglobal.h
index 9070f1fe8f17..899d68afc3c5 100644
--- a/drivers/acpi/acpica/acglobal.h
+++ b/drivers/acpi/acpica/acglobal.h
@@ -125,6 +125,14 @@ u8 ACPI_INIT_GLOBAL(acpi_gbl_enable_aml_debug_object, FALSE);
  */
 u8 ACPI_INIT_GLOBAL(acpi_gbl_copy_dsdt_locally, FALSE);
 
+/*
+ * Optionally truncate I/O addresses to 16 bits. Provides compatibility
+ * with other ACPI implementations. NOTE: During ACPICA initialization,
+ * this value is set to TRUE if any Windows OSI strings have been
+ * requested by the BIOS.
+ */
+u8 ACPI_INIT_GLOBAL(acpi_gbl_truncate_io_addresses, FALSE);
+
 /* acpi_gbl_FADT is a local copy of the FADT, converted to a common format. */
 
 struct acpi_table_fadt acpi_gbl_FADT;
diff --git a/drivers/acpi/acpica/hwvalid.c b/drivers/acpi/acpica/hwvalid.c
index c10d587c1641..e1d9c777b213 100644
--- a/drivers/acpi/acpica/hwvalid.c
+++ b/drivers/acpi/acpica/hwvalid.c
@@ -222,6 +222,12 @@ acpi_status acpi_hw_read_port(acpi_io_address address, u32 *value, u32 width)
 	u32 one_byte;
 	u32 i;
 
+	/* Truncate address to 16 bits if requested */
+
+	if (acpi_gbl_truncate_io_addresses) {
+		address &= ACPI_UINT16_MAX;
+	}
+
 	/* Validate the entire request and perform the I/O */
 
 	status = acpi_hw_validate_io_request(address, width);
@@ -279,6 +285,12 @@ acpi_status acpi_hw_write_port(acpi_io_address address, u32 value, u32 width)
 	acpi_status status;
 	u32 i;
 
+	/* Truncate address to 16 bits if requested */
+
+	if (acpi_gbl_truncate_io_addresses) {
+		address &= ACPI_UINT16_MAX;
+	}
+
 	/* Validate the entire request and perform the I/O */
 
 	status = acpi_hw_validate_io_request(address, width);
diff --git a/drivers/acpi/acpica/nsinit.c b/drivers/acpi/acpica/nsinit.c
index 9bd6f050f299..4e5272c313e0 100644
--- a/drivers/acpi/acpica/nsinit.c
+++ b/drivers/acpi/acpica/nsinit.c
@@ -193,6 +193,15 @@ acpi_status acpi_ns_initialize_devices(void)
 					acpi_ns_init_one_device, NULL, &info,
 					NULL);
 
+	/*
+	 * Any _OSI requests should be completed by now. If the BIOS has
+	 * requested any Windows OSI strings, we will always truncate
+	 * I/O addresses to 16 bits -- for Windows compatibility.
+	 */
+	if (acpi_gbl_osi_data >= ACPI_OSI_WIN_2000) {
+		acpi_gbl_truncate_io_addresses = TRUE;
+	}
+
 	ACPI_FREE(info.evaluate_info);
 	if (ACPI_FAILURE(status)) {
 		goto error_exit;