Initial import of Ralink/Mediatek MIPS SoC support #4

UART drivers.

- uart_dev_mtk.[ch] are the old-style Mediatek/Ralink-specific UART driver
  as also found in sys/mips/rt305x/uart_dev_rt305x.c, with minor improvements
  and FDT attachment enabled for the appropriate SoCs.
- uart_dev_mtk_ns8250.c is the new-style ns16550a-compatible UART driver
  found in newer Mediatek SoCs. It uses the uart_dev_ns8250.c driver
  indirectly and is basically just a wrapper around it and only overrides its
  probe method.
  The reason I am not using the uart_dev_ns8250.c driver directly is because
  I have some code that does UART clock detection before initializing the
  UART, so that we don't need to hard-code the UART clock frequency in the
  dts files for each board.

Approved by:	adrian (mentor)
Sponsored by:	Smartcom - Bulgaria AD
Differential Revision:	https://reviews.freebsd.org/D5840

3 files changed, 791 insertions, 0 deletions

diff --git a/sys/mips/mediatek/uart_dev_mtk.c b/sys/mips/mediatek/uart_dev_mtk.c
new file mode 100644
index 0000000..5993cb6
--- /dev/null
+++ b/sys/mips/mediatek/uart_dev_mtk.c
@@ -0,0 +1,552 @@
+/* $NetBSD: uart.c,v 1.2 2007/03/23 20:05:47 dogcow Exp $ */
+
+/*-
+ * Copyright (c) 2013, Alexander A. Mityaev <sansan@adm.ua>
+ * Copyright (c) 2010 Aleksandr Rybalko.
+ * Copyright (c) 2007 Ruslan Ermilov and Vsevolod Lobko.
+ * Copyright (c) 2007 Oleksandr Tymoshenko.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above
+ *    copyright notice, this list of conditions and the following
+ *    disclaimer in the documentation and/or other materials provided
+ *    with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+ * PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
+ * OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
+ * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
+ * TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
+ * OF SUCH DAMAGE.
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include "opt_ddb.h"
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/bus.h>
+#include <sys/conf.h>
+#include <sys/kdb.h>
+#include <sys/reboot.h>
+#include <sys/sysctl.h>
+#include <sys/kernel.h>
+#include <machine/bus.h>
+#include <machine/fdt.h>
+
+#include <dev/uart/uart.h>
+#include <dev/uart/uart_cpu.h>
+#include <dev/uart/uart_cpu_fdt.h>
+#include <dev/uart/uart_bus.h>
+
+#include <mips/mediatek/uart_dev_mtk.h>
+#include <mips/mediatek/mtk_soc.h>
+#include <mips/mediatek/mtk_sysctl.h>
+
+#include "uart_if.h"
+
+/* Set some reference clock value. Real value will be taken from FDT */
+#define DEFAULT_RCLK            (120 * 1000 * 1000)
+
+/*
+ * Low-level UART interface.
+ */
+static int mtk_uart_probe(struct uart_bas *bas);
+static void mtk_uart_init(struct uart_bas *bas, int, int, int, int);
+static void mtk_uart_term(struct uart_bas *bas);
+static void mtk_uart_putc(struct uart_bas *bas, int);
+static int mtk_uart_rxready(struct uart_bas *bas);
+static int mtk_uart_getc(struct uart_bas *bas, struct mtx *);
+
+static struct uart_ops uart_mtk_ops = {
+	.probe = mtk_uart_probe,
+	.init = mtk_uart_init,
+	.term = mtk_uart_term,
+	.putc = mtk_uart_putc,
+	.rxready = mtk_uart_rxready,
+	.getc = mtk_uart_getc,
+};
+
+static int	uart_output = 1;
+TUNABLE_INT("kern.uart_output", &uart_output);
+SYSCTL_INT(_kern, OID_AUTO, uart_output, CTLFLAG_RW,
+    &uart_output, 0, "UART output enabled.");
+
+static int
+mtk_uart_probe(struct uart_bas *bas)
+{
+	return (0);
+}
+
+static void
+mtk_uart_init(struct uart_bas *bas, int baudrate, int databits,
+    int stopbits, int parity)
+{
+        /* CLKDIV  = 384000000/ 3/ 16/ br */
+        /* for 384MHz CLKDIV = 8000000 / baudrate; */
+        switch (databits) {
+        case 5:
+    		databits = UART_LCR_5B;
+    		break;
+        case 6:
+    		databits = UART_LCR_6B;
+    		break;
+        case 7:
+    		databits = UART_LCR_7B;
+    		break;
+        case 8:
+    		databits = UART_LCR_8B;
+    		break;
+    	default:
+    		/* Unsupported */
+    		return;
+        }
+	switch (parity) {
+	case UART_PARITY_EVEN:	parity = (UART_LCR_PEN|UART_LCR_EVEN); break;
+	case UART_PARITY_ODD:	parity = (UART_LCR_PEN); break;
+	case UART_PARITY_NONE:	parity = 0; break;
+	/* Unsupported */
+	default:		return;
+	}
+
+	if (bas->rclk && baudrate) {
+        	uart_setreg(bas, UART_CDDL_REG, bas->rclk/16/baudrate);
+		uart_barrier(bas);
+	}
+
+        uart_setreg(bas, UART_LCR_REG, databits |
+				(stopbits==1?0:UART_LCR_STB_15) |
+       			 	parity);
+	uart_barrier(bas);
+}
+
+static void
+mtk_uart_term(struct uart_bas *bas)
+{
+        uart_setreg(bas, UART_MCR_REG, 0);
+	uart_barrier(bas);
+}
+
+static void
+mtk_uart_putc(struct uart_bas *bas, int c)
+{
+	char chr;
+	if (!uart_output) return;
+	chr = c;
+	while (!(uart_getreg(bas, UART_LSR_REG) & UART_LSR_THRE));
+	uart_setreg(bas, UART_TX_REG, c);
+	uart_barrier(bas);
+	while (!(uart_getreg(bas, UART_LSR_REG) & UART_LSR_THRE));
+}
+
+static int
+mtk_uart_rxready(struct uart_bas *bas)
+{
+	if (uart_getreg(bas, UART_LSR_REG) & UART_LSR_DR)
+		return (1);
+	return (0);
+}
+
+static int
+mtk_uart_getc(struct uart_bas *bas, struct mtx *hwmtx)
+{
+	int c;
+
+	uart_lock(hwmtx);
+
+	while (!(uart_getreg(bas, UART_LSR_REG) & UART_LSR_DR)) {
+		uart_unlock(hwmtx);
+		DELAY(10);
+		uart_lock(hwmtx);
+	}
+
+	c = uart_getreg(bas, UART_RX_REG);
+
+	uart_unlock(hwmtx);
+
+	return (c);
+}
+
+/*
+ * High-level UART interface.
+ */
+struct uart_mtk_softc {
+	struct uart_softc base;
+	uint8_t ier_mask;
+	uint8_t ier;
+};
+
+static int mtk_uart_bus_attach(struct uart_softc *);
+static int mtk_uart_bus_detach(struct uart_softc *);
+static int mtk_uart_bus_flush(struct uart_softc *, int);
+static int mtk_uart_bus_getsig(struct uart_softc *);
+static int mtk_uart_bus_ioctl(struct uart_softc *, int, intptr_t);
+static int mtk_uart_bus_ipend(struct uart_softc *);
+static int mtk_uart_bus_param(struct uart_softc *, int, int, int, int);
+static int mtk_uart_bus_probe(struct uart_softc *);
+static int mtk_uart_bus_receive(struct uart_softc *);
+static int mtk_uart_bus_setsig(struct uart_softc *, int);
+static int mtk_uart_bus_transmit(struct uart_softc *);
+static void mtk_uart_bus_grab(struct uart_softc *);
+static void mtk_uart_bus_ungrab(struct uart_softc *);
+
+static kobj_method_t uart_mtk_methods[] = {
+	KOBJMETHOD(uart_attach,		mtk_uart_bus_attach),
+	KOBJMETHOD(uart_detach,		mtk_uart_bus_detach),
+	KOBJMETHOD(uart_flush,		mtk_uart_bus_flush),
+	KOBJMETHOD(uart_getsig,		mtk_uart_bus_getsig),
+	KOBJMETHOD(uart_ioctl,		mtk_uart_bus_ioctl),
+	KOBJMETHOD(uart_ipend,		mtk_uart_bus_ipend),
+	KOBJMETHOD(uart_param,		mtk_uart_bus_param),
+	KOBJMETHOD(uart_probe,		mtk_uart_bus_probe),
+	KOBJMETHOD(uart_receive,	mtk_uart_bus_receive),
+	KOBJMETHOD(uart_setsig,		mtk_uart_bus_setsig),
+	KOBJMETHOD(uart_transmit,	mtk_uart_bus_transmit),
+	KOBJMETHOD(uart_grab,		mtk_uart_bus_grab),
+	KOBJMETHOD(uart_ungrab,		mtk_uart_bus_ungrab),
+	{ 0, 0 }
+};
+
+struct uart_class uart_mtk_class = {
+	"uart_mtk",
+	uart_mtk_methods,
+	sizeof(struct uart_mtk_softc),
+	.uc_ops = &uart_mtk_ops,
+	.uc_range = 1, /* use hinted range */
+	.uc_rclk = 0
+};
+
+static struct ofw_compat_data compat_data[] = {
+	{ "ralink,rt2880-uart",		(uintptr_t)&uart_mtk_class },
+	{ "ralink,rt3050-uart",		(uintptr_t)&uart_mtk_class },
+	{ "ralink,rt3352-uart",		(uintptr_t)&uart_mtk_class },
+	{ "ralink,rt3883-uart",		(uintptr_t)&uart_mtk_class },
+	{ "ralink,rt5350-uart",		(uintptr_t)&uart_mtk_class },
+	{ "ralink,mt7620a-uart",	(uintptr_t)&uart_mtk_class },
+	{ NULL,				(uintptr_t)NULL },
+};
+UART_FDT_CLASS_AND_DEVICE(compat_data);
+
+
+#define	SIGCHG(c, i, s, d)				\
+	if (c) {					\
+		i |= (i & s) ? s : s | d;		\
+	} else {					\
+		i = (i & s) ? (i & ~s) | d : i;		\
+	}
+
+/*
+ * Disable TX interrupt. uart should be locked
+ */
+static __inline void
+mtk_uart_disable_txintr(struct uart_softc *sc)
+{
+	struct uart_bas *bas = &sc->sc_bas;
+	uint8_t cr;
+
+	cr = uart_getreg(bas, UART_IER_REG);
+	cr &= ~UART_IER_ETBEI;
+	uart_setreg(bas, UART_IER_REG, cr);
+	uart_barrier(bas);
+}
+
+/*
+ * Enable TX interrupt. uart should be locked
+ */
+static __inline void
+mtk_uart_enable_txintr(struct uart_softc *sc)
+{
+	struct uart_bas *bas = &sc->sc_bas;
+	uint8_t cr;
+
+	cr = uart_getreg(bas, UART_IER_REG);
+	cr |= UART_IER_ETBEI;
+	uart_setreg(bas, UART_IER_REG, cr);
+	uart_barrier(bas);
+}
+
+static int
+mtk_uart_bus_attach(struct uart_softc *sc)
+{
+	struct uart_bas *bas;
+	struct uart_devinfo *di;
+	struct uart_mtk_softc *usc = (struct uart_mtk_softc *)sc;
+
+	bas = &sc->sc_bas;
+
+	if (!bas->rclk) {
+		bas->rclk = mtk_soc_get_uartclk();
+	}
+
+	if (sc->sc_sysdev != NULL) {
+		di = sc->sc_sysdev;
+		mtk_uart_init(bas, di->baudrate, di->databits, di->stopbits,
+		    di->parity);
+	} else {
+		mtk_uart_init(bas, 57600, 8, 1, 0);
+	}
+
+	sc->sc_rxfifosz = 16;
+	sc->sc_txfifosz = 16;
+
+	(void)mtk_uart_bus_getsig(sc);
+
+	/* Enable FIFO */
+	uart_setreg(bas, UART_FCR_REG,
+	    uart_getreg(bas, UART_FCR_REG) |
+	    UART_FCR_FIFOEN | UART_FCR_TXTGR_1 | UART_FCR_RXTGR_1);
+	uart_barrier(bas);
+	/* Enable interrupts */
+	usc->ier_mask = 0xf0;
+	uart_setreg(bas, UART_IER_REG,
+	    UART_IER_EDSSI | UART_IER_ELSI | UART_IER_ERBFI);
+	uart_barrier(bas);
+
+	return (0);
+}
+
+static int
+mtk_uart_bus_detach(struct uart_softc *sc)
+{
+	return (0);
+}
+
+static int
+mtk_uart_bus_flush(struct uart_softc *sc, int what)
+{
+	struct uart_bas *bas = &sc->sc_bas;
+	uint32_t fcr = uart_getreg(bas, UART_FCR_REG);
+
+	if (what & UART_FLUSH_TRANSMITTER) {
+		uart_setreg(bas, UART_FCR_REG, fcr|UART_FCR_TXRST);
+		uart_barrier(bas);
+	}
+	if (what & UART_FLUSH_RECEIVER) {
+		uart_setreg(bas, UART_FCR_REG, fcr|UART_FCR_RXRST);
+		uart_barrier(bas);
+	}
+	uart_setreg(bas, UART_FCR_REG, fcr);
+	uart_barrier(bas);
+	return (0);
+}
+
+static int
+mtk_uart_bus_getsig(struct uart_softc *sc)
+{
+	uint32_t new, old, sig;
+	uint8_t bes;
+
+	return(0);
+	do {
+		old = sc->sc_hwsig;
+		sig = old;
+		uart_lock(sc->sc_hwmtx);
+		bes = uart_getreg(&sc->sc_bas, UART_MSR_REG);
+		uart_unlock(sc->sc_hwmtx);
+		/* XXX: chip can show delta */
+		SIGCHG(bes & UART_MSR_CTS, sig, SER_CTS, SER_DCTS);
+		SIGCHG(bes & UART_MSR_DCD, sig, SER_DCD, SER_DDCD);
+		SIGCHG(bes & UART_MSR_DSR, sig, SER_DSR, SER_DDSR);
+		new = sig & ~SER_MASK_DELTA;
+	} while (!atomic_cmpset_32(&sc->sc_hwsig, old, new));
+
+	return (sig);
+}
+
+static int
+mtk_uart_bus_ioctl(struct uart_softc *sc, int request, intptr_t data)
+{
+	struct uart_bas *bas;
+	int baudrate, divisor, error;
+
+	bas = &sc->sc_bas;
+	error = 0;
+	uart_lock(sc->sc_hwmtx);
+	switch (request) {
+	case UART_IOCTL_BREAK:
+		/* TODO: Send BREAK */
+		break;
+	case UART_IOCTL_BAUD:
+		divisor = uart_getreg(bas, UART_CDDL_REG);
+		baudrate = bas->rclk / (divisor * 16);
+		*(int*)data = baudrate;
+		break;
+	default:
+		error = EINVAL;
+		break;
+	}
+	uart_unlock(sc->sc_hwmtx);
+	return (error);
+}
+
+static int
+mtk_uart_bus_ipend(struct uart_softc *sc)
+{
+	struct uart_bas *bas;
+	int ipend;
+	uint8_t iir, lsr, msr;
+
+//	breakpoint();
+
+	bas = &sc->sc_bas;
+	ipend = 0;
+
+	uart_lock(sc->sc_hwmtx);
+	iir = uart_getreg(&sc->sc_bas, UART_IIR_REG);
+	lsr = uart_getreg(&sc->sc_bas, UART_LSR_REG);
+	uart_setreg(&sc->sc_bas, UART_LSR_REG, lsr);
+	msr = uart_getreg(&sc->sc_bas, UART_MSR_REG);
+	uart_setreg(&sc->sc_bas, UART_MSR_REG, msr);
+	if (iir & UART_IIR_INTP) {
+		uart_unlock(sc->sc_hwmtx);
+		return (0);
+	}
+	switch ((iir >> 1) & 0x07) {
+	case UART_IIR_ID_THRE:
+		ipend |= SER_INT_TXIDLE;
+		break;
+	case UART_IIR_ID_DR2:
+		mtk_uart_bus_flush(sc, UART_FLUSH_RECEIVER);
+		/* passthrough */
+	case UART_IIR_ID_DR:
+		ipend |= SER_INT_RXREADY;
+		break;
+	case UART_IIR_ID_MST:
+	case UART_IIR_ID_LINESTATUS:
+		ipend |= SER_INT_SIGCHG;
+		if (lsr & UART_LSR_BI)
+			ipend |= SER_INT_BREAK;
+		if (lsr & UART_LSR_OE)
+			ipend |= SER_INT_OVERRUN;
+		break;
+	default:
+		/* XXX: maybe return error here */
+		break;
+	}
+
+	uart_unlock(sc->sc_hwmtx);
+
+	return (ipend);
+}
+
+static int
+mtk_uart_bus_param(struct uart_softc *sc, int baudrate, int databits,
+    int stopbits, int parity)
+{
+	uart_lock(sc->sc_hwmtx);
+	mtk_uart_init(&sc->sc_bas, baudrate, databits, stopbits, parity);
+	uart_unlock(sc->sc_hwmtx);
+	return (0);
+}
+
+static int
+mtk_uart_bus_probe(struct uart_softc *sc)
+{
+	int error;
+
+	error = mtk_uart_probe(&sc->sc_bas);
+	if (error)
+		return (error);
+		
+	device_set_desc(sc->sc_dev, "MTK UART Controller");
+
+	return (0);
+}
+
+static int
+mtk_uart_bus_receive(struct uart_softc *sc)
+{
+	struct uart_bas *bas;
+	int xc;
+	uint8_t lsr;
+
+	bas = &sc->sc_bas;
+	uart_lock(sc->sc_hwmtx);
+	lsr = uart_getreg(bas, UART_LSR_REG);
+	while ((lsr & UART_LSR_DR)) {
+		if (uart_rx_full(sc)) {
+			sc->sc_rxbuf[sc->sc_rxput] = UART_STAT_OVERRUN;
+			break;
+		}
+		xc = 0;
+		xc = uart_getreg(bas, UART_RX_REG);
+		if (lsr & UART_LSR_FE)
+			xc |= UART_STAT_FRAMERR;
+		if (lsr & UART_LSR_PE)
+			xc |= UART_STAT_PARERR;
+		if (lsr & UART_LSR_OE)
+			xc |= UART_STAT_OVERRUN;
+		uart_barrier(bas);
+		uart_rx_put(sc, xc);
+		lsr = uart_getreg(bas, UART_LSR_REG);
+	}
+
+	uart_unlock(sc->sc_hwmtx);
+	return (0);
+}
+
+static int
+mtk_uart_bus_setsig(struct uart_softc *sc, int sig)
+{
+	/* TODO: implement (?) */
+	return (sig);
+}
+
+static int
+mtk_uart_bus_transmit(struct uart_softc *sc)
+{
+	struct uart_bas *bas = &sc->sc_bas;
+	int i;
+
+	if (!uart_output) return (0);
+
+	bas = &sc->sc_bas;
+	uart_lock(sc->sc_hwmtx);
+	while ((uart_getreg(bas, UART_LSR_REG) & UART_LSR_THRE) == 0);
+	mtk_uart_enable_txintr(sc);
+	for (i = 0; i < sc->sc_txdatasz; i++) {
+		uart_setreg(bas, UART_TX_REG, sc->sc_txbuf[i]);
+		uart_barrier(bas);
+	}
+	sc->sc_txbusy = 1;
+	uart_unlock(sc->sc_hwmtx);
+	return (0);
+}
+
+void
+mtk_uart_bus_grab(struct uart_softc *sc)
+{
+	struct uart_bas *bas = &sc->sc_bas;
+	struct uart_mtk_softc *usc = (struct uart_mtk_softc *)sc;
+
+	uart_lock(sc->sc_hwmtx);
+	usc->ier = uart_getreg(bas, UART_IER_REG);
+	uart_setreg(bas, UART_IER_REG, usc->ier & usc->ier_mask);
+	uart_barrier(bas);
+	uart_unlock(sc->sc_hwmtx);
+}
+
+void
+mtk_uart_bus_ungrab(struct uart_softc *sc)
+{
+	struct uart_mtk_softc *usc = (struct uart_mtk_softc *)sc;
+	struct uart_bas *bas = &sc->sc_bas;
+
+	uart_lock(sc->sc_hwmtx);
+	uart_setreg(bas, UART_IER_REG, usc->ier);
+	uart_barrier(bas);
+	uart_unlock(sc->sc_hwmtx);
+}
diff --git a/sys/mips/mediatek/uart_dev_mtk.h b/sys/mips/mediatek/uart_dev_mtk.h
new file mode 100644
index 0000000..44fcdd8
--- /dev/null
+++ b/sys/mips/mediatek/uart_dev_mtk.h
@@ -0,0 +1,126 @@
+/*-
+ * Copyright (c) 2010 Aleksandr Rybalko.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above
+ *    copyright notice, this list of conditions and the following
+ *    disclaimer in the documentation and/or other materials provided
+ *    with the distribution.
+ * 3. The names of the authors may not be used to endorse or promote
+ *    products derived from this software without specific prior
+ *    written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+ * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+ * PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
+ * OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
+ * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR
+ * TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
+ * OF SUCH DAMAGE.
+ *
+ * $FreeBSD$
+ */
+#ifndef	_MTKUART_H
+#define	_MTKUART_H
+
+#undef	uart_getreg
+#undef	uart_setreg
+#define	uart_getreg(bas, reg)		\
+	bus_space_read_4((bas)->bst, (bas)->bsh, reg)
+#define	uart_setreg(bas, reg, value)	\
+	bus_space_write_4((bas)->bst, (bas)->bsh, reg, value)
+
+/* UART registers */
+#define	UART_RX_REG	0x00
+#define	UART_TX_REG	0x04
+
+#define	UART_IER_REG	0x08
+#define		UART_IER_EDSSI		(1<<3) /* Only full UART */
+#define		UART_IER_ELSI		(1<<2)
+#define		UART_IER_ETBEI		(1<<1)
+#define		UART_IER_ERBFI		(1<<0)
+
+#define	UART_IIR_REG	0x0c
+#define		UART_IIR_RXFIFO		(1<<7)
+#define		UART_IIR_TXFIFO		(1<<6)
+#define		UART_IIR_ID_MST		0
+#define		UART_IIR_ID_THRE	1
+#define		UART_IIR_ID_DR		2
+#define		UART_IIR_ID_LINESTATUS	3
+#define		UART_IIR_ID_DR2		6
+#define		UART_IIR_ID_SHIFT	1
+#define		UART_IIR_ID_MASK	0x0000000e
+#define		UART_IIR_INTP		(1<<0)
+
+#define	UART_FCR_REG	0x10
+#define		UART_FCR_RXTGR_1	(0<<6)
+#define		UART_FCR_RXTGR_4	(1<<6)
+#define		UART_FCR_RXTGR_8	(2<<6)
+#define		UART_FCR_RXTGR_12	(3<<6)
+#define		UART_FCR_TXTGR_1	(0<<4)
+#define		UART_FCR_TXTGR_4	(1<<4)
+#define		UART_FCR_TXTGR_8	(2<<4)
+#define		UART_FCR_TXTGR_12	(3<<4)
+#define		UART_FCR_DMA		(1<<3)
+#define		UART_FCR_TXRST		(1<<2)
+#define		UART_FCR_RXRST		(1<<1)
+#define		UART_FCR_FIFOEN		(1<<0)
+
+#define	UART_LCR_REG	0x14
+#define		UART_LCR_DLAB	(1<<7)
+#define		UART_LCR_BRK	(1<<6)
+#define		UART_LCR_FPAR	(1<<5)
+#define		UART_LCR_EVEN	(1<<4)
+#define		UART_LCR_PEN	(1<<3)
+#define		UART_LCR_STB_15	(1<<2)
+#define		UART_LCR_5B	0
+#define		UART_LCR_6B	1
+#define		UART_LCR_7B	2
+#define		UART_LCR_8B	3
+
+#define	UART_MCR_REG	0x18
+#define		UART_MCR_LOOP	(1<<4)
+#define		UART_MCR_OUT2_L	(1<<3) /* Only full UART */
+#define		UART_MCR_OUT1_L	(1<<2) /* Only full UART */
+#define		UART_MCR_RTS_L	(1<<1) /* Only full UART */
+#define		UART_MCR_DTR_L	(1<<0) /* Only full UART */
+
+#define	UART_LSR_REG	0x1c
+#define		UART_LSR_ERINF	(1<<7)
+#define		UART_LSR_TEMT	(1<<6)
+#define		UART_LSR_THRE	(1<<5)
+#define		UART_LSR_BI	(1<<4)
+#define		UART_LSR_FE	(1<<3)
+#define		UART_LSR_PE	(1<<2)
+#define		UART_LSR_OE	(1<<1)
+#define		UART_LSR_DR	(1<<0)
+
+#define	UART_MSR_REG	0x20 	/* Only full UART */
+#define		UART_MSR_DCD	(1<<7) /* Only full UART */
+#define		UART_MSR_RI	(1<<6) /* Only full UART */
+#define		UART_MSR_DSR	(1<<5) /* Only full UART */
+#define		UART_MSR_CTS	(1<<4) /* Only full UART */
+#define		UART_MSR_DDCD	(1<<3) /* Only full UART */
+#define		UART_MSR_TERI	(1<<2) /* Only full UART */
+#define		UART_MSR_DDSR	(1<<1) /* Only full UART */
+#define		UART_MSR_DCTS	(1<<0) /* Only full UART */
+
+#define	UART_CDDL_REG	0x28
+#define	UART_CDDLL_REG	0x2c
+#define	UART_CDDLH_REG	0x30
+
+#define	UART_IFCTL_REG	0x34
+#define		UART_IFCTL_IFCTL	(1<<0)
+
+int	uart_cnattach(void);
+#endif	/* _MTKUART_H */
diff --git a/sys/mips/mediatek/uart_dev_mtk_ns8250.c b/sys/mips/mediatek/uart_dev_mtk_ns8250.c
new file mode 100644
index 0000000..3c259ff
--- /dev/null
+++ b/sys/mips/mediatek/uart_dev_mtk_ns8250.c
@@ -0,0 +1,113 @@
+/*-
+ * Copyright (c) 2013 Ian Lepore
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "opt_platform.h"
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/bus.h>
+#include <sys/conf.h>
+#include <sys/kernel.h>
+#include <sys/sysctl.h>
+#include <machine/bus.h>
+
+#include <mips/mediatek/mtk_soc.h>
+#include <mips/mediatek/mtk_sysctl.h>
+
+#include <dev/fdt/fdt_common.h>
+#include <dev/ofw/ofw_bus.h>
+#include <dev/ofw/ofw_bus_subr.h>
+
+#include <dev/uart/uart.h>
+#include <dev/uart/uart_cpu.h>
+#include <dev/uart/uart_cpu_fdt.h>
+#include <dev/uart/uart_bus.h>
+#include <dev/uart/uart_dev_ns8250.h>
+
+#include "uart_if.h"
+
+/*
+ * High-level UART interface.
+ */
+static struct uart_class uart_mtk_ns8250_class;
+static int mtk_ns8250_bus_probe(struct uart_softc *);
+
+static kobj_method_t mtk_ns8250_methods[] = {
+	KOBJMETHOD(uart_probe,		mtk_ns8250_bus_probe),
+
+	KOBJMETHOD(uart_attach,		ns8250_bus_attach),
+	KOBJMETHOD(uart_detach,		ns8250_bus_detach),
+	KOBJMETHOD(uart_flush,		ns8250_bus_flush),
+	KOBJMETHOD(uart_getsig,		ns8250_bus_getsig),
+	KOBJMETHOD(uart_ioctl,		ns8250_bus_ioctl),
+	KOBJMETHOD(uart_ipend,		ns8250_bus_ipend),
+	KOBJMETHOD(uart_param,		ns8250_bus_param),
+	KOBJMETHOD(uart_receive,	ns8250_bus_receive),
+	KOBJMETHOD(uart_setsig,		ns8250_bus_setsig),
+	KOBJMETHOD(uart_transmit,	ns8250_bus_transmit),
+	KOBJMETHOD_END
+};
+
+static struct uart_class uart_mtk_ns8250_class = {
+	"mtk8250",
+	mtk_ns8250_methods,
+	sizeof(struct ns8250_softc),
+	.uc_ops = &uart_ns8250_ops,
+	.uc_range = 1, /* use hinted range */
+	.uc_rclk = 0,
+	.uc_rshift = 2
+};
+
+static struct ofw_compat_data compat_data[] = {
+	{ "mtk,ns16550a",	(uintptr_t)&uart_mtk_ns8250_class },
+	{ "ns16550a",		(uintptr_t)&uart_mtk_ns8250_class },
+	{ NULL,			(uintptr_t)NULL },
+};
+UART_FDT_CLASS_AND_DEVICE(compat_data);
+
+static int
+mtk_ns8250_bus_probe(struct uart_softc *sc)
+{       
+	int status;
+       
+	if (!ofw_bus_status_okay(sc->sc_dev))
+		return (ENXIO);
+        
+	if (ofw_bus_search_compatible(sc->sc_dev, compat_data)->ocd_data ==
+	    (uintptr_t)NULL)
+		return (ENXIO);
+        
+	sc->sc_bas.rclk = mtk_soc_get_uartclk();
+        
+	status = ns8250_bus_probe(sc);
+	if (status == 0)
+		device_set_desc(sc->sc_dev, "MTK UART Controller (ns16550a)");
+        
+	return (status);
+}