tty: of_serial: add no-loopback-test property

The loopback test mode is not implemented in all
NS16550 compatible UARTs. The 8250 driver uses the
UPF_SKIP_TEST flag to indicate this, however it is
not possible to set this flag via device-tree.

Add a new 'no-loopback-test' property, and modify
the of_serial driver to set the UPF_SKIP_TEST flag
if the property is present.

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 6 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/tty/serial/of-serial.txt b/Documentation/devicetree/bindings/tty/serial/of-serial.txt
index 0847fdeee11a..ba385f2e0ddc 100644
--- a/Documentation/devicetree/bindings/tty/serial/of-serial.txt
+++ b/Documentation/devicetree/bindings/tty/serial/of-serial.txt
@@ -25,6 +25,8 @@ Optional properties:
   accesses to the UART (e.g. TI davinci).
 - used-by-rtas : set to indicate that the port is in use by the OpenFirmware
   RTAS and should not be registered.
+- no-loopback-test: set to indicate that the port does not implements loopback
+  test mode
 
 Example:
 
diff --git a/drivers/tty/serial/of_serial.c b/drivers/tty/serial/of_serial.c
index ffc7879e85a4..df443b908ca3 100644
--- a/drivers/tty/serial/of_serial.c
+++ b/drivers/tty/serial/of_serial.c
@@ -105,6 +105,10 @@ static int __devinit of_platform_serial_setup(struct platform_device *ofdev,
         port->uartclk = clk;
         port->flags = UPF_SHARE_IRQ | UPF_BOOT_AUTOCONF | UPF_IOREMAP
                 | UPF_FIXED_PORT | UPF_FIXED_TYPE;
+
+        if (of_find_property(np, "no-loopback-test", NULL))
+                port->flags |= UPF_SKIP_TEST;
+
         port->dev = &ofdev->dev;
 
         if (type == PORT_TEGRA)