| Message ID | 20180420032947.23023-1-msalter@redhat.com (mailing list archive) |
|---|---|
| State | Rejected, archived |
| Headers | show |
On Fri, Apr 20, 2018 at 5:29 AM, Mark Salter <msalter@redhat.com> 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 <msalter@redhat.com> > --- > 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, > -- -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Sun, 2018-04-22 at 11:34 +0200, Rafael J. Wysocki wrote: > On Fri, Apr 20, 2018 at 5:29 AM, Mark Salter <msalter@redhat.com> 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. It is unfortunate but the firmware bug predates the change which uncovered it, so previously working systems no longer work. > > > 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 <msalter@redhat.com> > > --- > > 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? The device ID will always be used for X-Gene UARTs. Whether the DSDT is broken or not wouldn't matter because the end result would be the same (the UART being treated as master rather than a serial bus slave). The broken firmware looks like this: Device (URT0) { Name (_HID, "APMC0D08") // _HID: Hardware ID ... Name (_CRS, ResourceTemplate () // _CRS: Current Resource Settings { Memory32Fixed (ReadWrite, 0x1C020000, // Address Base 0x00000100, // Address Length ) UartSerialBusV2 (0x0001C200, DataBitsEight, StopBitsOne, 0x00, LittleEndian, ParityTypeNone, FlowControlNone, 0x0010, 0x0010, "URT0", 0x00, ResourceConsumer, , Exclusive, ) Interrupt (ResourceConsumer, Level, ActiveHigh, Exclusive, ,, ) { 0x0000006D, } }) ... } So "URT0" has a UartSerialBusV2 resource which references itself as the bus master. > > > + > > INIT_LIST_HEAD(&resource_list); > > acpi_dev_get_resources(device, &resource_list, > > acpi_check_serial_bus_slave, > > -- -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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; + INIT_LIST_HEAD(&resource_list); acpi_dev_get_resources(device, &resource_list, acpi_check_serial_bus_slave,
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 <msalter@redhat.com> --- drivers/acpi/scan.c | 8 ++++++++ 1 file changed, 8 insertions(+)