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>

1 files changed, 972 insertions, 0 deletions

diff --git a/drivers/serial/sb1250-duart.c b/drivers/serial/sb1250-duart.c
new file mode 100644
index 000000000000..1d9d7285172a
--- /dev/null
+++ b/drivers/serial/sb1250-duart.c
@@ -0,0 +1,972 @@
+/*
+ *      drivers/serial/sb1250-duart.c
+ *
+ *      Support for the asynchronous serial interface (DUART) included
+ *      in the BCM1250 and derived System-On-a-Chip (SOC) devices.
+ *
+ *      Copyright (c) 2007  Maciej W. Rozycki
+ *
+ *      Derived from drivers/char/sb1250_duart.c for which the following
+ *      copyright applies:
+ *
+ *      Copyright (c) 2000, 2001, 2002, 2003, 2004  Broadcom Corporation
+ *
+ *      This program is free software; you can redistribute it and/or
+ *      modify it under the terms of the GNU General Public License
+ *      as published by the Free Software Foundation; either version
+ *      2 of the License, or (at your option) any later version.
+ *
+ *      References:
+ *
+ *      "BCM1250/BCM1125/BCM1125H User Manual", Broadcom Corporation
+ */
+
+#if defined(CONFIG_SERIAL_SB1250_DUART_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ)
+#define SUPPORT_SYSRQ
+#endif
+
+#include <linux/console.h>
+#include <linux/delay.h>
+#include <linux/errno.h>
+#include <linux/init.h>
+#include <linux/interrupt.h>
+#include <linux/ioport.h>
+#include <linux/kernel.h>
+#include <linux/major.h>
+#include <linux/serial.h>
+#include <linux/serial_core.h>
+#include <linux/spinlock.h>
+#include <linux/sysrq.h>
+#include <linux/tty.h>
+#include <linux/types.h>
+
+#include <asm/atomic.h>
+#include <asm/io.h>
+#include <asm/war.h>
+
+#include <asm/sibyte/sb1250.h>
+#include <asm/sibyte/sb1250_uart.h>
+#include <asm/sibyte/swarm.h>
+
+
+#if defined(CONFIG_SIBYTE_BCM1x55) || defined(CONFIG_SIBYTE_BCM1x80)
+#include <asm/sibyte/bcm1480_regs.h>
+#include <asm/sibyte/bcm1480_int.h>
+
+#define SBD_CHANREGS(line)      A_BCM1480_DUART_CHANREG((line), 0)
+#define SBD_CTRLREGS(line)      A_BCM1480_DUART_CTRLREG((line), 0)
+#define SBD_INT(line)           (K_BCM1480_INT_UART_0 + (line))
+
+#elif defined(CONFIG_SIBYTE_SB1250) || defined(CONFIG_SIBYTE_BCM112X)
+#include <asm/sibyte/sb1250_regs.h>
+#include <asm/sibyte/sb1250_int.h>
+
+#define SBD_CHANREGS(line)      A_DUART_CHANREG((line), 0)
+#define SBD_CTRLREGS(line)      A_DUART_CTRLREG(0)
+#define SBD_INT(line)           (K_INT_UART_0 + (line))
+
+#else
+#error invalid SB1250 UART configuration
+
+#endif
+
+
+MODULE_AUTHOR("Maciej W. Rozycki <macro@linux-mips.org>");
+MODULE_DESCRIPTION("BCM1xxx on-chip DUART serial driver");
+MODULE_LICENSE("GPL");
+
+
+#define DUART_MAX_CHIP 2
+#define DUART_MAX_SIDE 2
+
+/*
+ * Per-port state.
+ */
+struct sbd_port {
+        struct sbd_duart        *duart;
+        struct uart_port        port;
+        unsigned char __iomem   *memctrl;
+        int                     tx_stopped;
+        int                     initialised;
+};
+
+/*
+ * Per-DUART state for the shared register space.
+ */
+struct sbd_duart {
+        struct sbd_port         sport[2];
+        unsigned long           mapctrl;
+        atomic_t                map_guard;
+};
+
+#define to_sport(uport) container_of(uport, struct sbd_port, port)
+
+static struct sbd_duart sbd_duarts[DUART_MAX_CHIP];
+
+#define __unused __attribute__((__unused__))
+
+
+/*
+ * Reading and writing SB1250 DUART registers.
+ *
+ * There are three register spaces: two per-channel ones and
+ * a shared one.  We have to define accessors appropriately.
+ * All registers are 64-bit and all but the Baud Rate Clock
+ * registers only define 8 least significant bits.  There is
+ * also a workaround to take into account.  Raw accessors use
+ * the full register width, but cooked ones truncate it
+ * intentionally so that the rest of the driver does not care.
+ */
+static u64 __read_sbdchn(struct sbd_port *sport, int reg)
+{
+        void __iomem *csr = sport->port.membase + reg;
+
+        return __raw_readq(csr);
+}
+
+static u64 __read_sbdshr(struct sbd_port *sport, int reg)
+{
+        void __iomem *csr = sport->memctrl + reg;
+
+        return __raw_readq(csr);
+}
+
+static void __write_sbdchn(struct sbd_port *sport, int reg, u64 value)
+{
+        void __iomem *csr = sport->port.membase + reg;
+
+        __raw_writeq(value, csr);
+}
+
+static void __write_sbdshr(struct sbd_port *sport, int reg, u64 value)
+{
+        void __iomem *csr = sport->memctrl + reg;
+
+        __raw_writeq(value, csr);
+}
+
+/*
+ * In bug 1956, we get glitches that can mess up uart registers.  This
+ * "read-mode-reg after any register access" is an accepted workaround.
+ */
+static void __war_sbd1956(struct sbd_port *sport)
+{
+        __read_sbdchn(sport, R_DUART_MODE_REG_1);
+        __read_sbdchn(sport, R_DUART_MODE_REG_2);
+}
+
+static unsigned char read_sbdchn(struct sbd_port *sport, int reg)
+{
+        unsigned char retval;
+
+        retval = __read_sbdchn(sport, reg);
+        if (SIBYTE_1956_WAR)
+                __war_sbd1956(sport);
+        return retval;
+}
+
+static unsigned char read_sbdshr(struct sbd_port *sport, int reg)
+{
+        unsigned char retval;
+
+        retval = __read_sbdshr(sport, reg);
+        if (SIBYTE_1956_WAR)
+                __war_sbd1956(sport);
+        return retval;
+}
+
+static void write_sbdchn(struct sbd_port *sport, int reg, unsigned int value)
+{
+        __write_sbdchn(sport, reg, value);
+        if (SIBYTE_1956_WAR)
+                __war_sbd1956(sport);
+}
+
+static void write_sbdshr(struct sbd_port *sport, int reg, unsigned int value)
+{
+        __write_sbdshr(sport, reg, value);
+        if (SIBYTE_1956_WAR)
+                __war_sbd1956(sport);
+}
+
+
+static int sbd_receive_ready(struct sbd_port *sport)
+{
+        return read_sbdchn(sport, R_DUART_STATUS) & M_DUART_RX_RDY;
+}
+
+static int sbd_receive_drain(struct sbd_port *sport)
+{
+        int loops = 10000;
+
+        while (sbd_receive_ready(sport) && loops--)
+                read_sbdchn(sport, R_DUART_RX_HOLD);
+        return loops;
+}
+
+static int __unused sbd_transmit_ready(struct sbd_port *sport)
+{
+        return read_sbdchn(sport, R_DUART_STATUS) & M_DUART_TX_RDY;
+}
+
+static int __unused sbd_transmit_drain(struct sbd_port *sport)
+{
+        int loops = 10000;
+
+        while (!sbd_transmit_ready(sport) && loops--)
+                udelay(2);
+        return loops;
+}
+
+static int sbd_transmit_empty(struct sbd_port *sport)
+{
+        return read_sbdchn(sport, R_DUART_STATUS) & M_DUART_TX_EMT;
+}
+
+static int sbd_line_drain(struct sbd_port *sport)
+{
+        int loops = 10000;
+
+        while (!sbd_transmit_empty(sport) && loops--)
+                udelay(2);
+        return loops;
+}
+
+
+static unsigned int sbd_tx_empty(struct uart_port *uport)
+{
+        struct sbd_port *sport = to_sport(uport);
+
+        return sbd_transmit_empty(sport) ? TIOCSER_TEMT : 0;
+}
+
+static unsigned int sbd_get_mctrl(struct uart_port *uport)
+{
+        struct sbd_port *sport = to_sport(uport);
+        unsigned int mctrl, status;
+
+        status = read_sbdshr(sport, R_DUART_IN_PORT);
+        status >>= (uport->line) % 2;
+        mctrl = (!(status & M_DUART_IN_PIN0_VAL) ? TIOCM_CTS : 0) |
+                (!(status & M_DUART_IN_PIN4_VAL) ? TIOCM_CAR : 0) |
+                (!(status & M_DUART_RIN0_PIN) ? TIOCM_RNG : 0) |
+                (!(status & M_DUART_IN_PIN2_VAL) ? TIOCM_DSR : 0);
+        return mctrl;
+}
+
+static void sbd_set_mctrl(struct uart_port *uport, unsigned int mctrl)
+{
+        struct sbd_port *sport = to_sport(uport);
+        unsigned int clr = 0, set = 0, mode2;
+
+        if (mctrl & TIOCM_DTR)
+                set |= M_DUART_SET_OPR2;
+        else
+                clr |= M_DUART_CLR_OPR2;
+        if (mctrl & TIOCM_RTS)
+                set |= M_DUART_SET_OPR0;
+        else
+                clr |= M_DUART_CLR_OPR0;
+        clr <<= (uport->line) % 2;
+        set <<= (uport->line) % 2;
+
+        mode2 = read_sbdchn(sport, R_DUART_MODE_REG_2);
+        mode2 &= ~M_DUART_CHAN_MODE;
+        if (mctrl & TIOCM_LOOP)
+                mode2 |= V_DUART_CHAN_MODE_LCL_LOOP;
+        else
+                mode2 |= V_DUART_CHAN_MODE_NORMAL;
+
+        write_sbdshr(sport, R_DUART_CLEAR_OPR, clr);
+        write_sbdshr(sport, R_DUART_SET_OPR, set);
+        write_sbdchn(sport, R_DUART_MODE_REG_2, mode2);
+}
+
+static void sbd_stop_tx(struct uart_port *uport)
+{
+        struct sbd_port *sport = to_sport(uport);
+
+        write_sbdchn(sport, R_DUART_CMD, M_DUART_TX_DIS);
+        sport->tx_stopped = 1;
+};
+
+static void sbd_start_tx(struct uart_port *uport)
+{
+        struct sbd_port *sport = to_sport(uport);
+        unsigned int mask;
+
+        /* Enable tx interrupts.  */
+        mask = read_sbdshr(sport, R_DUART_IMRREG((uport->line) % 2));
+        mask |= M_DUART_IMR_TX;
+        write_sbdshr(sport, R_DUART_IMRREG((uport->line) % 2), mask);
+
+        /* Go!, go!, go!...  */
+        write_sbdchn(sport, R_DUART_CMD, M_DUART_TX_EN);
+        sport->tx_stopped = 0;
+};
+
+static void sbd_stop_rx(struct uart_port *uport)
+{
+        struct sbd_port *sport = to_sport(uport);
+
+        write_sbdshr(sport, R_DUART_IMRREG((uport->line) % 2), 0);
+};
+
+static void sbd_enable_ms(struct uart_port *uport)
+{
+        struct sbd_port *sport = to_sport(uport);
+
+        write_sbdchn(sport, R_DUART_AUXCTL_X,
+                     M_DUART_CIN_CHNG_ENA | M_DUART_CTS_CHNG_ENA);
+}
+
+static void sbd_break_ctl(struct uart_port *uport, int break_state)
+{
+        struct sbd_port *sport = to_sport(uport);
+
+        if (break_state == -1)
+                write_sbdchn(sport, R_DUART_CMD, V_DUART_MISC_CMD_START_BREAK);
+        else
+                write_sbdchn(sport, R_DUART_CMD, V_DUART_MISC_CMD_STOP_BREAK);
+}
+
+
+static void sbd_receive_chars(struct sbd_port *sport)
+{
+        struct uart_port *uport = &sport->port;
+        struct uart_icount *icount;
+        unsigned int status, ch, flag;
+        int count;
+
+        for (count = 16; count; count--) {
+                status = read_sbdchn(sport, R_DUART_STATUS);
+                if (!(status & M_DUART_RX_RDY))
+                        break;
+
+                ch = read_sbdchn(sport, R_DUART_RX_HOLD);
+
+                flag = TTY_NORMAL;
+
+                icount = &uport->icount;
+                icount->rx++;
+
+                if (unlikely(status &
+                             (M_DUART_RCVD_BRK | M_DUART_FRM_ERR |
+                              M_DUART_PARITY_ERR | M_DUART_OVRUN_ERR))) {
+                        if (status & M_DUART_RCVD_BRK) {
+                                icount->brk++;
+                                if (uart_handle_break(uport))
+                                        continue;
+                        } else if (status & M_DUART_FRM_ERR)
+                                icount->frame++;
+                        else if (status & M_DUART_PARITY_ERR)
+                                icount->parity++;
+                        if (status & M_DUART_OVRUN_ERR)
+                                icount->overrun++;
+
+                        status &= uport->read_status_mask;
+                        if (status & M_DUART_RCVD_BRK)
+                                flag = TTY_BREAK;
+                        else if (status & M_DUART_FRM_ERR)
+                                flag = TTY_FRAME;
+                        else if (status & M_DUART_PARITY_ERR)
+                                flag = TTY_PARITY;
+                }
+
+                if (uart_handle_sysrq_char(uport, ch))
+                        continue;
+
+                uart_insert_char(uport, status, M_DUART_OVRUN_ERR, ch, flag);
+        }
+
+        tty_flip_buffer_push(uport->info->tty);
+}
+
+static void sbd_transmit_chars(struct sbd_port *sport)
+{
+        struct uart_port *uport = &sport->port;
+        struct circ_buf *xmit = &sport->port.info->xmit;
+        unsigned int mask;
+        int stop_tx;
+
+        /* XON/XOFF chars.  */
+        if (sport->port.x_char) {
+                write_sbdchn(sport, R_DUART_TX_HOLD, sport->port.x_char);
+                sport->port.icount.tx++;
+                sport->port.x_char = 0;
+                return;
+        }
+
+        /* If nothing to do or stopped or hardware stopped.  */
+        stop_tx = (uart_circ_empty(xmit) || uart_tx_stopped(&sport->port));
+
+        /* Send char.  */
+        if (!stop_tx) {
+                write_sbdchn(sport, R_DUART_TX_HOLD, xmit->buf[xmit->tail]);
+                xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
+                sport->port.icount.tx++;
+
+                if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
+                        uart_write_wakeup(&sport->port);
+        }
+
+        /* Are we are done?  */
+        if (stop_tx || uart_circ_empty(xmit)) {
+                /* Disable tx interrupts.  */
+                mask = read_sbdshr(sport, R_DUART_IMRREG((uport->line) % 2));
+                mask &= ~M_DUART_IMR_TX;
+                write_sbdshr(sport, R_DUART_IMRREG((uport->line) % 2), mask);
+        }
+}
+
+static void sbd_status_handle(struct sbd_port *sport)
+{
+        struct uart_port *uport = &sport->port;
+        unsigned int delta;
+
+        delta = read_sbdshr(sport, R_DUART_INCHREG((uport->line) % 2));
+        delta >>= (uport->line) % 2;
+
+        if (delta & (M_DUART_IN_PIN0_VAL << S_DUART_IN_PIN_CHNG))
+                uart_handle_cts_change(uport, !(delta & M_DUART_IN_PIN0_VAL));
+
+        if (delta & (M_DUART_IN_PIN2_VAL << S_DUART_IN_PIN_CHNG))
+                uport->icount.dsr++;
+
+        if (delta & ((M_DUART_IN_PIN2_VAL | M_DUART_IN_PIN0_VAL) <<
+                     S_DUART_IN_PIN_CHNG))
+                wake_up_interruptible(&uport->info->delta_msr_wait);
+}
+
+static irqreturn_t sbd_interrupt(int irq, void *dev_id)
+{
+        struct sbd_port *sport = dev_id;
+        struct uart_port *uport = &sport->port;
+        irqreturn_t status = IRQ_NONE;
+        unsigned int intstat;
+        int count;
+
+        for (count = 16; count; count--) {
+                intstat = read_sbdshr(sport,
+                                      R_DUART_ISRREG((uport->line) % 2));
+                intstat &= read_sbdshr(sport,
+                                       R_DUART_IMRREG((uport->line) % 2));
+                intstat &= M_DUART_ISR_ALL;
+                if (!intstat)
+                        break;
+
+                if (intstat & M_DUART_ISR_RX)
+                        sbd_receive_chars(sport);
+                if (intstat & M_DUART_ISR_IN)
+                        sbd_status_handle(sport);
+                if (intstat & M_DUART_ISR_TX)
+                        sbd_transmit_chars(sport);
+
+                status = IRQ_HANDLED;
+        }
+
+        return status;
+}
+
+
+static int sbd_startup(struct uart_port *uport)
+{
+        struct sbd_port *sport = to_sport(uport);
+        unsigned int mode1;
+        int ret;
+
+        ret = request_irq(sport->port.irq, sbd_interrupt,
+                          IRQF_SHARED, "sb1250-duart", sport);
+        if (ret)
+                return ret;
+
+        /* Clear the receive FIFO.  */
+        sbd_receive_drain(sport);
+
+        /* Clear the interrupt registers.  */
+        write_sbdchn(sport, R_DUART_CMD, V_DUART_MISC_CMD_RESET_BREAK_INT);
+        read_sbdshr(sport, R_DUART_INCHREG((uport->line) % 2));
+
+        /* Set rx/tx interrupt to FIFO available.  */
+        mode1 = read_sbdchn(sport, R_DUART_MODE_REG_1);
+        mode1 &= ~(M_DUART_RX_IRQ_SEL_RXFULL | M_DUART_TX_IRQ_SEL_TXEMPT);
+        write_sbdchn(sport, R_DUART_MODE_REG_1, mode1);
+
+        /* Disable tx, enable rx.  */
+        write_sbdchn(sport, R_DUART_CMD, M_DUART_TX_DIS | M_DUART_RX_EN);
+        sport->tx_stopped = 1;
+
+        /* Enable interrupts.  */
+        write_sbdshr(sport, R_DUART_IMRREG((uport->line) % 2),
+                     M_DUART_IMR_IN | M_DUART_IMR_RX);
+
+        return 0;
+}
+
+static void sbd_shutdown(struct uart_port *uport)
+{
+        struct sbd_port *sport = to_sport(uport);
+
+        write_sbdchn(sport, R_DUART_CMD, M_DUART_TX_DIS | M_DUART_RX_DIS);
+        sport->tx_stopped = 1;
+        free_irq(sport->port.irq, sport);
+}
+
+
+static void sbd_init_port(struct sbd_port *sport)
+{
+        struct uart_port *uport = &sport->port;
+
+        if (sport->initialised)
+                return;
+
+        /* There is no DUART reset feature, so just set some sane defaults.  */
+        write_sbdchn(sport, R_DUART_CMD, V_DUART_MISC_CMD_RESET_TX);
+        write_sbdchn(sport, R_DUART_CMD, V_DUART_MISC_CMD_RESET_RX);
+        write_sbdchn(sport, R_DUART_MODE_REG_1, V_DUART_BITS_PER_CHAR_8);
+        write_sbdchn(sport, R_DUART_MODE_REG_2, 0);
+        write_sbdchn(sport, R_DUART_FULL_CTL,
+                     V_DUART_INT_TIME(0) | V_DUART_SIG_FULL(15));
+        write_sbdchn(sport, R_DUART_OPCR_X, 0);
+        write_sbdchn(sport, R_DUART_AUXCTL_X, 0);
+        write_sbdshr(sport, R_DUART_IMRREG((uport->line) % 2), 0);
+
+        sport->initialised = 1;
+}
+
+static void sbd_set_termios(struct uart_port *uport, struct ktermios *termios,
+                            struct ktermios *old_termios)
+{
+        struct sbd_port *sport = to_sport(uport);
+        unsigned int mode1 = 0, mode2 = 0, aux = 0;
+        unsigned int mode1mask = 0, mode2mask = 0, auxmask = 0;
+        unsigned int oldmode1, oldmode2, oldaux;
+        unsigned int baud, brg;
+        unsigned int command;
+
+        mode1mask |= ~(M_DUART_PARITY_MODE | M_DUART_PARITY_TYPE_ODD |
+                       M_DUART_BITS_PER_CHAR);
+        mode2mask |= ~M_DUART_STOP_BIT_LEN_2;
+        auxmask |= ~M_DUART_CTS_CHNG_ENA;
+
+        /* Byte size.  */
+        switch (termios->c_cflag & CSIZE) {
+        case CS5:
+        case CS6:
+                /* Unsupported, leave unchanged.  */
+                mode1mask |= M_DUART_PARITY_MODE;
+                break;
+        case CS7:
+                mode1 |= V_DUART_BITS_PER_CHAR_7;
+                break;
+        case CS8:
+        default:
+                mode1 |= V_DUART_BITS_PER_CHAR_8;
+                break;
+        }
+
+        /* Parity and stop bits.  */
+        if (termios->c_cflag & CSTOPB)
+                mode2 |= M_DUART_STOP_BIT_LEN_2;
+        else
+                mode2 |= M_DUART_STOP_BIT_LEN_1;
+        if (termios->c_cflag & PARENB)
+                mode1 |= V_DUART_PARITY_MODE_ADD;
+        else
+                mode1 |= V_DUART_PARITY_MODE_NONE;
+        if (termios->c_cflag & PARODD)
+                mode1 |= M_DUART_PARITY_TYPE_ODD;
+        else
+                mode1 |= M_DUART_PARITY_TYPE_EVEN;
+
+        baud = uart_get_baud_rate(uport, termios, old_termios, 1200, 5000000);
+        brg = V_DUART_BAUD_RATE(baud);
+        /* The actual lower bound is 1221bps, so compensate.  */
+        if (brg > M_DUART_CLK_COUNTER)
+                brg = M_DUART_CLK_COUNTER;
+
+        uart_update_timeout(uport, termios->c_cflag, baud);
+
+        uport->read_status_mask = M_DUART_OVRUN_ERR;
+        if (termios->c_iflag & INPCK)
+                uport->read_status_mask |= M_DUART_FRM_ERR |
+                                           M_DUART_PARITY_ERR;
+        if (termios->c_iflag & (BRKINT | PARMRK))
+                uport->read_status_mask |= M_DUART_RCVD_BRK;
+
+        uport->ignore_status_mask = 0;
+        if (termios->c_iflag & IGNPAR)
+                uport->ignore_status_mask |= M_DUART_FRM_ERR |
+                                             M_DUART_PARITY_ERR;
+        if (termios->c_iflag & IGNBRK) {
+                uport->ignore_status_mask |= M_DUART_RCVD_BRK;
+                if (termios->c_iflag & IGNPAR)
+                        uport->ignore_status_mask |= M_DUART_OVRUN_ERR;
+        }
+
+        if (termios->c_cflag & CREAD)
+                command = M_DUART_RX_EN;
+        else
+                command = M_DUART_RX_DIS;
+
+        if (termios->c_cflag & CRTSCTS)
+                aux |= M_DUART_CTS_CHNG_ENA;
+        else
+                aux &= ~M_DUART_CTS_CHNG_ENA;
+
+        spin_lock(&uport->lock);
+
+        if (sport->tx_stopped)
+                command |= M_DUART_TX_DIS;
+        else
+                command |= M_DUART_TX_EN;
+
+        oldmode1 = read_sbdchn(sport, R_DUART_MODE_REG_1) & mode1mask;
+        oldmode2 = read_sbdchn(sport, R_DUART_MODE_REG_2) & mode2mask;
+        oldaux = read_sbdchn(sport, R_DUART_AUXCTL_X) & auxmask;
+
+        if (!sport->tx_stopped)
+                sbd_line_drain(sport);
+        write_sbdchn(sport, R_DUART_CMD, M_DUART_TX_DIS | M_DUART_RX_DIS);
+
+        write_sbdchn(sport, R_DUART_MODE_REG_1, mode1 | oldmode1);
+        write_sbdchn(sport, R_DUART_MODE_REG_2, mode2 | oldmode2);
+        write_sbdchn(sport, R_DUART_CLK_SEL, brg);
+        write_sbdchn(sport, R_DUART_AUXCTL_X, aux | oldaux);
+
+        write_sbdchn(sport, R_DUART_CMD, command);
+
+        spin_unlock(&uport->lock);
+}
+
+
+static const char *sbd_type(struct uart_port *uport)
+{
+        return "SB1250 DUART";
+}
+
+static void sbd_release_port(struct uart_port *uport)
+{
+        struct sbd_port *sport = to_sport(uport);
+        struct sbd_duart *duart = sport->duart;
+        int map_guard;
+
+        iounmap(sport->memctrl);
+        sport->memctrl = NULL;
+        iounmap(uport->membase);
+        uport->membase = NULL;
+
+        map_guard = atomic_add_return(-1, &duart->map_guard);
+        if (!map_guard)
+                release_mem_region(duart->mapctrl, DUART_CHANREG_SPACING);
+        release_mem_region(uport->mapbase, DUART_CHANREG_SPACING);
+}
+
+static int sbd_map_port(struct uart_port *uport)
+{
+        static const char *err = KERN_ERR "sbd: Cannot map MMIO\n";
+        struct sbd_port *sport = to_sport(uport);
+        struct sbd_duart *duart = sport->duart;
+
+        if (!uport->membase)
+                uport->membase = ioremap_nocache(uport->mapbase,
+                                                 DUART_CHANREG_SPACING);
+        if (!uport->membase) {
+                printk(err);
+                return -ENOMEM;
+        }
+
+        if (!sport->memctrl)
+                sport->memctrl = ioremap_nocache(duart->mapctrl,
+                                                 DUART_CHANREG_SPACING);
+        if (!sport->memctrl) {
+                printk(err);
+                iounmap(uport->membase);
+                uport->membase = NULL;
+                return -ENOMEM;
+        }
+
+        return 0;
+}
+
+static int sbd_request_port(struct uart_port *uport)
+{
+        static const char *err = KERN_ERR
+                                 "sbd: Unable to reserve MMIO resource\n";
+        struct sbd_duart *duart = to_sport(uport)->duart;
+        int map_guard;
+        int ret = 0;
+
+        if (!request_mem_region(uport->mapbase, DUART_CHANREG_SPACING,
+                                "sb1250-duart")) {
+                printk(err);
+                return -EBUSY;
+        }
+        map_guard = atomic_add_return(1, &duart->map_guard);
+        if (map_guard == 1) {
+                if (!request_mem_region(duart->mapctrl, DUART_CHANREG_SPACING,
+                                        "sb1250-duart")) {
+                        atomic_add(-1, &duart->map_guard);
+                        printk(err);
+                        ret = -EBUSY;
+                }
+        }
+        if (!ret) {
+                ret = sbd_map_port(uport);
+                if (ret) {
+                        map_guard = atomic_add_return(-1, &duart->map_guard);
+                        if (!map_guard)
+                                release_mem_region(duart->mapctrl,
+                                                   DUART_CHANREG_SPACING);
+                }
+        }
+        if (ret) {
+                release_mem_region(uport->mapbase, DUART_CHANREG_SPACING);
+                return ret;
+        }
+        return 0;
+}
+
+static void sbd_config_port(struct uart_port *uport, int flags)
+{
+        struct sbd_port *sport = to_sport(uport);
+
+        if (flags & UART_CONFIG_TYPE) {
+                if (sbd_request_port(uport))
+                        return;
+
+                uport->type = PORT_SB1250_DUART;
+
+                sbd_init_port(sport);
+        }
+}
+
+static int sbd_verify_port(struct uart_port *uport, struct serial_struct *ser)
+{
+        int ret = 0;
+
+        if (ser->type != PORT_UNKNOWN && ser->type != PORT_SB1250_DUART)
+                ret = -EINVAL;
+        if (ser->irq != uport->irq)
+                ret = -EINVAL;
+        if (ser->baud_base != uport->uartclk / 16)
+                ret = -EINVAL;
+        return ret;
+}
+
+
+static struct uart_ops sbd_ops = {
+        .tx_empty       = sbd_tx_empty,
+        .set_mctrl      = sbd_set_mctrl,
+        .get_mctrl      = sbd_get_mctrl,
+        .stop_tx        = sbd_stop_tx,
+        .start_tx       = sbd_start_tx,
+        .stop_rx        = sbd_stop_rx,
+        .enable_ms      = sbd_enable_ms,
+        .break_ctl      = sbd_break_ctl,
+        .startup        = sbd_startup,
+        .shutdown       = sbd_shutdown,
+        .set_termios    = sbd_set_termios,
+        .type           = sbd_type,
+        .release_port   = sbd_release_port,
+        .request_port   = sbd_request_port,
+        .config_port    = sbd_config_port,
+        .verify_port    = sbd_verify_port,
+};
+
+/* Initialize SB1250 DUART port structures.  */
+static void __init sbd_probe_duarts(void)
+{
+        static int probed;
+        int chip, side;
+        int max_lines, line;
+
+        if (probed)
+                return;
+
+        /* Set the number of available units based on the SOC type.  */
+        switch (soc_type) {
+        case K_SYS_SOC_TYPE_BCM1x55:
+        case K_SYS_SOC_TYPE_BCM1x80:
+                max_lines = 4;
+                break;
+        default:
+                /* Assume at least two serial ports at the normal address.  */
+                max_lines = 2;
+                break;
+        }
+
+        probed = 1;
+
+        for (chip = 0, line = 0; chip < DUART_MAX_CHIP && line < max_lines;
+             chip++) {
+                sbd_duarts[chip].mapctrl = SBD_CTRLREGS(line);
+
+                for (side = 0; side < DUART_MAX_SIDE && line < max_lines;
+                     side++, line++) {
+                        struct sbd_port *sport = &sbd_duarts[chip].sport[side];
+                        struct uart_port *uport = &sport->port;
+
+                        sport->duart    = &sbd_duarts[chip];
+
+                        uport->irq      = SBD_INT(line);
+                        uport->uartclk  = 100000000 / 20 * 16;
+                        uport->fifosize = 16;
+                        uport->iotype   = UPIO_MEM;
+                        uport->flags    = UPF_BOOT_AUTOCONF;
+                        uport->ops      = &sbd_ops;
+                        uport->line     = line;
+                        uport->mapbase  = SBD_CHANREGS(line);
+                }
+        }
+}
+
+
+#ifdef CONFIG_SERIAL_SB1250_DUART_CONSOLE
+/*
+ * Serial console stuff.  Very basic, polling driver for doing serial
+ * console output.  The console_sem is held by the caller, so we
+ * shouldn't be interrupted for more console activity.
+ */
+static void sbd_console_putchar(struct uart_port *uport, int ch)
+{
+        struct sbd_port *sport = to_sport(uport);
+
+        sbd_transmit_drain(sport);
+        write_sbdchn(sport, R_DUART_TX_HOLD, ch);
+}
+
+static void sbd_console_write(struct console *co, const char *s,
+                              unsigned int count)
+{
+        int chip = co->index / DUART_MAX_SIDE;
+        int side = co->index % DUART_MAX_SIDE;
+        struct sbd_port *sport = &sbd_duarts[chip].sport[side];
+        struct uart_port *uport = &sport->port;
+        unsigned long flags;
+        unsigned int mask;
+
+        /* Disable transmit interrupts and enable the transmitter. */
+        spin_lock_irqsave(&uport->lock, flags);
+        mask = read_sbdshr(sport, R_DUART_IMRREG((uport->line) % 2));
+        write_sbdshr(sport, R_DUART_IMRREG((uport->line) % 2),
+                     mask & ~M_DUART_IMR_TX);
+        write_sbdchn(sport, R_DUART_CMD, M_DUART_TX_EN);
+        spin_unlock_irqrestore(&uport->lock, flags);
+
+        uart_console_write(&sport->port, s, count, sbd_console_putchar);
+
+        /* Restore transmit interrupts and the transmitter enable. */
+        spin_lock_irqsave(&uport->lock, flags);
+        sbd_line_drain(sport);
+        if (sport->tx_stopped)
+                write_sbdchn(sport, R_DUART_CMD, M_DUART_TX_DIS);
+        write_sbdshr(sport, R_DUART_IMRREG((uport->line) % 2), mask);
+        spin_unlock_irqrestore(&uport->lock, flags);
+}
+
+static int __init sbd_console_setup(struct console *co, char *options)
+{
+        int chip = co->index / DUART_MAX_SIDE;
+        int side = co->index % DUART_MAX_SIDE;
+        struct sbd_port *sport = &sbd_duarts[chip].sport[side];
+        struct uart_port *uport = &sport->port;
+        int baud = 115200;
+        int bits = 8;
+        int parity = 'n';
+        int flow = 'n';
+        int ret;
+
+        if (!sport->duart)
+                return -ENXIO;
+
+        ret = sbd_map_port(uport);
+        if (ret)
+                return ret;
+
+        sbd_init_port(sport);
+
+        if (options)
+                uart_parse_options(options, &baud, &parity, &bits, &flow);
+        return uart_set_options(uport, co, baud, parity, bits, flow);
+}
+
+static struct uart_driver sbd_reg;
+static struct console sbd_console = {
+        .name   = "duart",
+        .write  = sbd_console_write,
+        .device = uart_console_device,
+        .setup  = sbd_console_setup,
+        .flags  = CON_PRINTBUFFER,
+        .index  = -1,
+        .data   = &sbd_reg
+};
+
+static int __init sbd_serial_console_init(void)
+{
+        sbd_probe_duarts();
+        register_console(&sbd_console);
+
+        return 0;
+}
+
+console_initcall(sbd_serial_console_init);
+
+#define SERIAL_SB1250_DUART_CONSOLE     &sbd_console
+#else
+#define SERIAL_SB1250_DUART_CONSOLE     NULL
+#endif /* CONFIG_SERIAL_SB1250_DUART_CONSOLE */
+
+
+static struct uart_driver sbd_reg = {
+        .owner          = THIS_MODULE,
+        .driver_name    = "serial",
+        .dev_name       = "duart",
+        .major          = TTY_MAJOR,
+        .minor          = SB1250_DUART_MINOR_BASE,
+        .nr             = DUART_MAX_CHIP * DUART_MAX_SIDE,
+        .cons           = SERIAL_SB1250_DUART_CONSOLE,
+};
+
+/* Set up the driver and register it.  */
+static int __init sbd_init(void)
+{
+        int i, ret;
+
+        sbd_probe_duarts();
+
+        ret = uart_register_driver(&sbd_reg);
+        if (ret)
+                return ret;
+
+        for (i = 0; i < DUART_MAX_CHIP * DUART_MAX_SIDE; i++) {
+                struct sbd_duart *duart = &sbd_duarts[i / DUART_MAX_SIDE];
+                struct sbd_port *sport = &duart->sport[i % DUART_MAX_SIDE];
+                struct uart_port *uport = &sport->port;
+
+                if (sport->duart)
+                        uart_add_one_port(&sbd_reg, uport);
+        }
+
+        return 0;
+}
+
+/* Unload the driver.  Unregister stuff, get ready to go away.  */
+static void __exit sbd_exit(void)
+{
+        int i;
+
+        for (i = DUART_MAX_CHIP * DUART_MAX_SIDE - 1; i >= 0; i--) {
+                struct sbd_duart *duart = &sbd_duarts[i / DUART_MAX_SIDE];
+                struct sbd_port *sport = &duart->sport[i % DUART_MAX_SIDE];
+                struct uart_port *uport = &sport->port;
+
+                if (sport->duart)
+                        uart_remove_one_port(&sbd_reg, uport);
+        }
+
+        uart_unregister_driver(&sbd_reg);
+}
+
+module_init(sbd_init);
+module_exit(sbd_exit);