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From patchwork Fri Apr 20 03:29:47 2018
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Content-Type: text/plain; charset="utf-8"
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MIME-Version: 1.0
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Content-Transfer-Encoding: 7bit
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Subject: ACPI / scan: Fix regression related to X-Gene UARTs
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From: Mark Salter <msalter@redhat.com>
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X-Patchwork-Id: 10351797
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Message-Id: <20180420032947.23023-1-msalter@redhat.com>
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To: =?UTF-8?q?Fr=C3=A9d=C3=A9ric=20Danis?= <frederic.danis.oss@gmail.com>
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Cc: "Rafael J . Wysocki" <rjw@rjwysocki.net>,
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linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org
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Date: Thu, 19 Apr 2018 23:29:47 -0400
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Commit e361d1f85855 ("ACPI / scan: Fix enumeration for special UART
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devices") caused a regression with some X-Gene based platforms (Mustang
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and M400) with invalid DSDT. The DSDT makes it appear that the UART
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device is also a slave device attached to itself. With the above commit
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the UART won't be enumerated by ACPI scan (slave serial devices shouldn't
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be). So check for X-Gene UART device and skip slace device check on it.
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Signed-off-by: Mark Salter <msalter@redhat.com>
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---
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drivers/acpi/scan.c | 8 ++++++++
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1 file changed, 8 insertions(+)
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diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
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index cc234e6a6297..1dcdd0122862 100644
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--- a/drivers/acpi/scan.c
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+++ b/drivers/acpi/scan.c
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@@ -1551,6 +1551,14 @@ static bool acpi_device_enumeration_by_parent(struct acpi_device *device)
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fwnode_property_present(&device->fwnode, "baud")))
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return true;
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+ /*
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+ * Firmware on some arm64 X-Gene platforms will make the UART
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+ * device appear as both a UART and a slave of that UART. Just
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+ * bail out here for X-Gene UARTs.
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+ */
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+ if (!strcmp(acpi_device_hid(device), "APMC0D08"))
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+ return false;
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+
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INIT_LIST_HEAD(&resource_list);
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acpi_dev_get_resources(device, &resource_list,
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acpi_check_serial_bus_slave,
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