From: Shannon Zhao <redacted>

ACPI 6.0 introduces a new table STAO to list the devices which are used
by Xen and can't be used by Dom0. On Xen virtual platforms, the physical
UART is used by Xen. So here it hides UART from Dom0.

Signed-off-by: Shannon Zhao <redacted>
---
CC: "Rafael J. Wysocki" <redacted> (supporter:ACPI)
CC: Len Brown <lenb@kernel.org> (supporter:ACPI)
CC: linux-acpi at vger.kernel.org (open list:ACPI)
---
 drivers/acpi/bus.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
index a212cef..d7a559f 100644
--- a/drivers/acpi/bus.c
+++ b/drivers/acpi/bus.c

@@ -46,6 +46,7 @@ ACPI_MODULE_NAME("bus");
 struct acpi_device *acpi_root;
 struct proc_dir_entry *acpi_root_dir;
 EXPORT_SYMBOL(acpi_root_dir);
+static u64 spcr_uart_addr;
 
 #ifdef CONFIG_X86
 #ifdef CONFIG_ACPI_CUSTOM_DSDT

@@ -93,6 +94,17 @@ acpi_status acpi_bus_get_status_handle(acpi_handle handle,
 {
 	acpi_status status;
 
+	if (spcr_uart_addr != 0xffffffffffffffff) {

+		u64 addr;
+
+		status = acpi_evaluate_integer(handle, METHOD_NAME__ADR, NULL,
+					       &addr);
+		if (ACPI_SUCCESS(status) && (addr == spcr_uart_addr)) {
+			*sta = 0;
+			return AE_OK;
+		}
+	}
+
 	status = acpi_evaluate_integer(handle, "_STA", NULL, sta);
 	if (ACPI_SUCCESS(status))
 		return AE_OK;

@@ -1069,6 +1081,8 @@ EXPORT_SYMBOL_GPL(acpi_kobj);
 static int __init acpi_init(void)
 {
 	int result;
+	acpi_status status;
+	struct acpi_table_stao *stao_ptr;
 
 	if (acpi_disabled) {
 		printk(KERN_INFO PREFIX "Interpreter disabled.\n");

@@ -1081,6 +1095,22 @@ static int __init acpi_init(void)
 		acpi_kobj = NULL;
 	}
 
+	/* If there is STAO table, check whether it needs to ignore the UART
+	 * device in SPCR table.
+	 */
+	spcr_uart_addr = 0xffffffffffffffff;
+	status = acpi_get_table(ACPI_SIG_STAO, 0,
+				(struct acpi_table_header **)&stao_ptr);
+	if (ACPI_SUCCESS(status)) {
+		if (stao_ptr->ignore_uart) {
+			struct acpi_table_spcr *spcr_ptr;
+
+			acpi_get_table(ACPI_SIG_SPCR, 0,
+				       (struct acpi_table_header **)&spcr_ptr);
+			spcr_uart_addr = spcr_ptr->serial_port.address;
+		}
+	}
+
 	init_acpi_device_notify();
 	result = acpi_bus_init();
 	if (result) {

-- 
2.0.4


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