serial: ralink: adds support for the serial core found on ralink wisoc

The MIPS based Ralink WiSoC platform has 1 or more 8250 compatible serial cores.
To make them work we require the same quirks that are used by AU1x00.
Signed-off-by: John Crispin <blogic@openwrt.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/8250/8250.c

@@ -317,9 +317,9 @@ static void default_serial_dl_write(struct uart_8250_port *up, int value)
 	serial_out(up, UART_DLM, value >> 8 & 0xff);
 }
 
-#ifdef CONFIG_MIPS_ALCHEMY
+#if defined(CONFIG_MIPS_ALCHEMY) || defined(CONFIG_SERIAL_8250_RT288X)
 
-/* Au1x00 UART hardware has a weird register layout */
+/* Au1x00/RT288x UART hardware has a weird register layout */
 static const u8 au_io_in_map[] = {
 	[UART_RX]  = 0,
 	[UART_IER] = 2,
@@ -440,7 +440,7 @@ static void set_io_from_upio(struct uart_port *p)
 		p->serial_out = mem32_serial_out;
 		break;
 
-#ifdef CONFIG_MIPS_ALCHEMY
+#if defined(CONFIG_MIPS_ALCHEMY) || defined(CONFIG_SERIAL_8250_RT288X)
 	case UPIO_AU:
 		p->serial_in = au_serial_in;
 		p->serial_out = au_serial_out;

drivers/tty/serial/8250/Kconfig

@@ -276,3 +276,11 @@ config SERIAL_8250_EM
 	  Selecting this option will add support for the integrated serial
 	  port hardware found on the Emma Mobile line of processors.
 	  If unsure, say N.
+
+config SERIAL_8250_RT288X
+	bool "Ralink RT288x/RT305x/RT3662/RT3883 serial port support"
+	depends on SERIAL_8250 && (SOC_RT288X || SOC_RT305X || SOC_RT3883)
+	help
+	  If you have a Ralink RT288x/RT305x SoC based board and want to use the
+	  serial port, say Y to this option. The driver can handle up to 2 serial
+	  ports. If unsure, say N.

include/linux/serial_core.h

@@ -134,7 +134,7 @@ struct uart_port {
 #define UPIO_HUB6		(1)
 #define UPIO_MEM		(2)
 #define UPIO_MEM32		(3)
-#define UPIO_AU			(4)			/* Au1x00 type IO */
+#define UPIO_AU			(4)			/* Au1x00 and RT288x type IO */
 #define UPIO_TSI		(5)			/* Tsi108/109 type IO */
 
 	unsigned int		read_status_mask;	/* driver specific */