From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Rafael J. Wysocki" Subject: Re: [PATCH] ACPI / scan: Fix regression related to X-Gene UARTs Date: Sun, 22 Apr 2018 11:34:06 +0200 Message-ID: References: <20180420032947.23023-1-msalter@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: In-Reply-To: <20180420032947.23023-1-msalter@redhat.com> Sender: linux-kernel-owner@vger.kernel.org To: Mark Salter Cc: =?UTF-8?B?RnLDqWTDqXJpYyBEYW5pcw==?= , "Rafael J . Wysocki" , ACPI Devel Maling List , Linux Kernel Mailing List List-Id: linux-acpi@vger.kernel.org On Fri, Apr 20, 2018 at 5:29 AM, Mark Salter wrote: > 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. I'm not convinced that making changes to the core ACPI device enumeration code in order to cover up for firmware bugs is the right approach. > 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; Is the device ID never to be used outside of the broken configurations? Even if that's the plan, how are you going to guarantee that anyway? > + > INIT_LIST_HEAD(&resource_list); > acpi_dev_get_resources(device, &resource_list, > acpi_check_serial_bus_slave, > --