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/*-

 * Copyright (c) 2009, Kohsuke Ohtani

 * 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. Neither the name of the author nor the names of any co-contributors

 *    may be used to endorse or promote products derived from this software

 *    without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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.

 */

/*

 * ns16550.c - NS16550 serial driver

 */

#include <driver.h>

#include <tty.h>

#include <serial.h>

/* #define DEBUG_NS16550 1 */

#ifdef DEBUG_NS16550

#define DPRINTF(a) printf a

#else

#define DPRINTF(a)

#endif

#define COM_BASE        CONFIG_NS16550_BASE

#define COM_IRQ                CONFIG_NS16550_IRQ

/* Register offsets */

#define COM_RBR                (COM_BASE + 0x00)        /* receive buffer register */

#define COM_THR                (COM_BASE + 0x00)        /* transmit holding register */

#define COM_IER                (COM_BASE + 0x01)        /* interrupt enable register */

#define COM_FCR                (COM_BASE + 0x02)        /* FIFO control register */

#define COM_IIR                (COM_BASE + 0x02)        /* interrupt identification register */

#define COM_LCR                (COM_BASE + 0x03)        /* line control register */

#define COM_MCR                (COM_BASE + 0x04)        /* modem control register */

#define COM_LSR                (COM_BASE + 0x05)        /* line status register */

#define COM_MSR                (COM_BASE + 0x06)        /* modem status register */

#define COM_DLL                (COM_BASE + 0x00)        /* divisor latch LSB (LCR[7] = 1) */

#define COM_DLM                (COM_BASE + 0x01)        /* divisor latch MSB (LCR[7] = 1) */

/* Interrupt enable register */

#define        IER_RDA                0x01        /* enable receive data available */

#define        IER_THRE        0x02        /* enable transmitter holding register empty */

#define        IER_RLS                0x04        /* enable recieve line status */

#define        IER_RMS                0x08        /* enable receive modem status */

/* Interrupt identification register */

#define        IIR_MSR                0x00        /* modem status change */

#define        IIR_IP                0x01        /* 0 when interrupt pending */

#define        IIR_TXB                0x02        /* transmitter holding register empty */

#define        IIR_RXB                0x04        /* received data available */

#define        IIR_LSR                0x06        /* line status change */

#define        IIR_MASK        0x07        /* mask off just the meaningful bits */

/* line status register */

#define        LSR_RCV_FIFO        0x80

#define        LSR_TSRE        0x40        /* Transmitter empty: byte sent */

#define        LSR_TXRDY        0x20        /* Transmitter buffer empty */

#define        LSR_BI                0x10        /* Break detected */

#define        LSR_FE                0x08        /* Framing error: bad stop bit */

#define        LSR_PE                0x04        /* Parity error */

#define        LSR_OE                0x02        /* Overrun, lost incoming byte */

#define        LSR_RXRDY        0x01        /* Byte ready in Receive Buffer */

#define        LSR_RCV_MASK        0x1f        /* Mask for incoming data or error */

/* Forward functions */

static int        ns16550_probe(struct driver *);

static int        ns16550_init(struct driver *);

static void        ns16550_xmt_char(struct serial_port *, char);

static char        ns16550_rcv_char(struct serial_port *);

static void        ns16550_set_poll(struct serial_port *, int);

static void        ns16550_start(struct serial_port *);

static void        ns16550_stop(struct serial_port *);

struct driver ns16550_driver = {

        /* name */        "ns16550",

        /* devops */        NULL,

        /* devsz */        0,

        /* flags */        0,

        /* probe */        ns16550_probe,

        /* init */        ns16550_init,

        /* unload */        NULL,

};

static struct serial_ops ns16550_ops = {

        /* xmt_char */        ns16550_xmt_char,

        /* rcv_char */        ns16550_rcv_char,

        /* set_poll */        ns16550_set_poll,

        /* start */        ns16550_start,

        /* stop */        ns16550_stop,

};

static struct serial_port ns16550_port;

static void

ns16550_xmt_char(struct serial_port *sp, char c)

{

        while (!(bus_read_8(COM_LSR) & LSR_TXRDY))

                ;

        bus_write_8(COM_THR, c);

}

static char

ns16550_rcv_char(struct serial_port *sp)

{

        while (!(bus_read_8(COM_LSR) & LSR_RXRDY))

                ;

        return bus_read_8(COM_RBR);

}

static void

ns16550_set_poll(struct serial_port *sp, int on)

{

        if (on) {

                /* Disable interrupt for polling mode. */

                bus_write_8(COM_IER, 0x00);

        } else {

                /* enable interrupt again */

                bus_write_8(COM_IER, IER_RDA|IER_THRE|IER_RLS);

        }

}

static int

ns16550_isr(void *arg)

{

        struct serial_port *sp = arg;

        switch (bus_read_8(COM_IIR) & IIR_MASK) {

        case IIR_MSR:                /* Modem status change */

                break;

        case IIR_LSR:                /* Line status change */

                bus_read_8(COM_LSR);

                break;

        case IIR_TXB:                /* Transmitter holding register empty */

                serial_xmt_done(sp);

                break;

        case IIR_RXB:                /* Received data available */

                bus_read_8(COM_LSR);

                serial_rcv_char(sp, bus_read_8(COM_RBR));

                break;

        }

        return 0;

}

static void

ns16550_start(struct serial_port *sp)

{

        int s;

        bus_write_8(COM_IER, 0x00);        /* Disable interrupt */

        bus_write_8(COM_LCR, 0x80);        /* Access baud rate */

        bus_write_8(COM_DLL, 0x01);        /* 115200 baud */

        bus_write_8(COM_DLM, 0x00);

        bus_write_8(COM_LCR, 0x03);        /* N, 8, 1 */

        bus_write_8(COM_FCR, 0x06);        /* Disable & clear FIFO */

        sp->irq = irq_attach(COM_IRQ, IPL_COMM, 0, ns16550_isr,

                             IST_NONE, sp);

        s = splhigh();

        bus_write_8(COM_MCR, 0x0b);  /* Enable OUT2 interrupt */

        bus_write_8(COM_IER, IER_RDA|IER_THRE|IER_RLS);  /* Enable interrupt */

        bus_read_8(COM_IIR);

        splx(s);

}

static void

ns16550_stop(struct serial_port *sp)

{

        /* Disable all interrupts */

        bus_write_8(COM_IER, 0x00);

}

static int

ns16550_probe(struct driver *self)

{

        if (bus_read_8(COM_LSR) == 0xff)

                return ENXIO;        /* Port is disabled */

        return 0;

}

static int

ns16550_init(struct driver *self)

{

        serial_attach(&ns16550_ops, &ns16550_port);

        return 0;

}