sb1250-duart.c: SB1250 DUART serial support

This is a driver for the SB1250 DUART, a dual serial port implementation
included in the Broadcom family of SOCs descending from the SiByte SB1250
MIPS64 chip multiprocessor.  It is a new implementation replacing the
old-fashioned driver currently present in the linux-mips.org tree.  It
supports all the usual features one would expect from a(n asynchronous)
serial driver, including modem line control (as far as hardware supports it
-- there is edge detection logic missing from the DCD and RI lines and the
driver does not implement polling of these lines at the moment), the serial
console, BREAK transmission and reception, including the magic SysRq.  The
receive FIFO threshold is not maintained though.

The driver was tested with a SWARM board which uses a BCM1250 SOC (which is
dual MIPS64 CMP) and has both ports of the single DUART implemented wired
externally.  Both were tested.  Testing included using the ports as
terminal lines at 1200bps (which is the ports minimum), 115200bps and a
couple of random speeds inbetween.  The modem lines were verified to
operate correctly.  No testing was performed with a use as a network
interface, like with SLIP or PPP.

Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Acked-by: Ralf Baechle <ralf@linux-mips.org>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/mips/sibyte/bcm1480/setup.c

@@ -31,6 +31,7 @@
 unsigned int sb1_pass;
 unsigned int soc_pass;
 unsigned int soc_type;
+EXPORT_SYMBOL(soc_type);
 unsigned int periph_rev;
 unsigned int zbbus_mhz;
 

arch/mips/sibyte/sb1250/setup.c

@@ -31,6 +31,7 @@
 unsigned int sb1_pass;
 unsigned int soc_pass;
 unsigned int soc_type;
+EXPORT_SYMBOL(soc_type);
 unsigned int periph_rev;
 unsigned int zbbus_mhz;
 EXPORT_SYMBOL(zbbus_mhz);

drivers/serial/Kconfig

@@ -338,6 +338,34 @@ config SERIAL_AMBA_PL011_CONSOLE
 	  your boot loader (lilo or loadlin) about how to pass options to the
 	  kernel at boot time.)
 
+config SERIAL_SB1250_DUART
+	tristate "BCM1xxx on-chip DUART serial support"
+	depends on SIBYTE_SB1xxx_SOC=y
+	select SERIAL_CORE
+	default y
+	---help---
+	  Support for the asynchronous serial interface (DUART) included in
+	  the BCM1250 and derived System-On-a-Chip (SOC) devices.  Note that
+	  the letter D in DUART stands for "dual", which is how the device
+	  is implemented.  Depending on the SOC configuration there may be
+	  one or more DUARTs available of which all are handled.
+
+	  If unsure, say Y.  To compile this driver as a module, choose M here:
+	  the module will be called sb1250-duart.
+
+config SERIAL_SB1250_DUART_CONSOLE
+	bool "Support for console on a BCM1xxx DUART serial port"
+	depends on SERIAL_SB1250_DUART=y
+	select SERIAL_CORE_CONSOLE
+	default y
+	---help---
+	  If you say Y here, it will be possible to use a serial port as the
+	  system console (the system console is the device which receives all
+	  kernel messages and warnings and which allows logins in single user
+	  mode).
+
+	  If unsure, say Y.
+
 config SERIAL_ATMEL
 	bool "AT91 / AT32 on-chip serial port support"
 	depends on (ARM && ARCH_AT91) || AVR32

drivers/serial/Makefile

@@ -51,6 +51,7 @@ obj-$(CONFIG_SERIAL_MPC52xx) += mpc52xx_uart.o
 obj-$(CONFIG_SERIAL_ICOM) += icom.o
 obj-$(CONFIG_SERIAL_M32R_SIO) += m32r_sio.o
 obj-$(CONFIG_SERIAL_MPSC) += mpsc.o
+obj-$(CONFIG_SERIAL_SB1250_DUART) += sb1250-duart.o
 obj-$(CONFIG_ETRAX_SERIAL) += crisv10.o
 obj-$(CONFIG_SERIAL_JSM) += jsm/
 obj-$(CONFIG_SERIAL_TXX9) += serial_txx9.o