From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Mark Salter <msalter@redhat.com>
Date: Thu, 10 May 2018 17:38:44 -0400
Subject: [PATCH] aarch64: acpi scan: Fix regression related to X-Gene UARTs

Message-id: <20180510173844.29580-4-msalter@redhat.com>
Patchwork-id: 214381
O-Subject: [RHEL-8 BZ1519554 3/3] aarch64: acpi scan: Fix regression related to X-Gene UARTs
Bugzilla: 1519554
RH-Acked-by: Al Stone <astone@redhat.com>
RH-Acked-by: Tony Camuso <tcamuso@redhat.com>

Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1519554
Brew: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=16144520

Commit e361d1f85855 ("ACPI / scan: Fix enumeration for special UART
devices") caused a regression with some X-Gene based platforms (Mustang
and M400) with invalid DSDT. The DSDT makes it appear that the UART
device is also a slave device attached to itself. With the above commit
the UART won't be enumerated by ACPI scan (slave serial devices shouldn't
be). So check for X-Gene UART device and skip slace device check on it.

Upstream Status: RHEL only
Signed-off-by: Mark Salter <msalter@redhat.com>
Signed-off-by: Herton R. Krzesinski <herton@redhat.com>
---
 drivers/acpi/scan.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 2142f1554761..f5fdf6f3650c 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -1614,6 +1614,15 @@ static bool acpi_device_enumeration_by_parent(struct acpi_device *device)
 	if (!acpi_match_device_ids(device, ignore_serial_bus_ids))
 		return false;
 
+	/*
+	 * Firmware on some arm64 X-Gene platforms will make the UART
+	 * device appear as both a UART and a slave of that UART. Just
+	 * bail out here for X-Gene UARTs.
+	 */
+	if (IS_ENABLED(CONFIG_ARM64) &&
+	    !strcmp(acpi_device_hid(device), "APMC0D08"))
+		return false;
+
 	INIT_LIST_HEAD(&resource_list);
 	acpi_dev_get_resources(device, &resource_list,
 			       acpi_check_serial_bus_slave,
-- 
2.28.0