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From: Mark Salter <>
To: "Frédéric Danis" <>
Cc: "Rafael J . Wysocki" <>,,
Subject: [PATCH] ACPI / scan: Fix regression related to X-Gene UARTs
Date: Thu, 19 Apr 2018 23:29:47 -0400	[thread overview]
Message-ID: <> (raw)

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.

Signed-off-by: Mark Salter <>
 drivers/acpi/scan.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index cc234e6a6297..1dcdd0122862 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -1551,6 +1551,14 @@ static bool acpi_device_enumeration_by_parent(struct acpi_device *device)
 	     fwnode_property_present(&device->fwnode, "baud")))
 		return true;
+	/*
+	 * 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 (!strcmp(acpi_device_hid(device), "APMC0D08"))
+		return false;
 	acpi_dev_get_resources(device, &resource_list,

             reply	other threads:[~2018-04-20  3:30 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-20  3:29 Mark Salter [this message]
2018-04-22  9:34 ` [PATCH] ACPI / scan: Fix regression related to X-Gene UARTs Rafael J. Wysocki
2018-04-27 18:24   ` Mark Salter

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