[PATCH 4.9 087/118] serial: 8250_of: assume reg-shift of 2 for mrvl,mmp-uart

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Lubomir Rintel <lkundrak@v3.sk>

commit f4817843e39ce78aace0195a57d4e8500a65a898 upstream.

There are two other drivers that bind to mrvl,mmp-uart and both of them
assume register shift of 2 bits. There are device trees that lack the
property and rely on that assumption.

If this driver wins the race to bind to those devices, it should behave
the same as the older deprecated driver.

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/tty/serial/8250/8250_of.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/drivers/tty/serial/8250/8250_of.c
+++ b/drivers/tty/serial/8250/8250_of.c
@@ -97,6 +97,10 @@ static int of_platform_serial_setup(stru
 	if (of_property_read_u32(np, "reg-offset", &prop) == 0)
 		port->mapbase += prop;
 
+	/* Compatibility with the deprecated pxa driver and 8250_pxa drivers. */
+	if (of_device_is_compatible(np, "mrvl,mmp-uart"))
+		port->regshift = 2;
+
 	/* Check for registers offset within the devices address range */
 	if (of_property_read_u32(np, "reg-shift", &prop) == 0)
 		port->regshift = prop;