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/*

 * QEMU 16450 UART emulation

 * 

 * Copyright (c) 2003-2004 Fabrice Bellard

 * 

 * Permission is hereby granted, free of charge, to any person obtaining a copy

 * of this software and associated documentation files (the "Software"), to deal

 * in the Software without restriction, including without limitation the rights

 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

 * copies of the Software, and to permit persons to whom the Software is

 * furnished to do so, subject to the following conditions:

 *

 * The above copyright notice and this permission notice shall be included in

 * all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL

 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

 * THE SOFTWARE.

 */

#include "vl.h"

//#define DEBUG_SERIAL

#define UART_LCR_DLAB        0x80        /* Divisor latch access bit */

#define UART_IER_MSI        0x08        /* Enable Modem status interrupt */

#define UART_IER_RLSI        0x04        /* Enable receiver line status interrupt */

#define UART_IER_THRI        0x02        /* Enable Transmitter holding register int. */

#define UART_IER_RDI        0x01        /* Enable receiver data interrupt */

#define UART_IIR_NO_INT        0x01        /* No interrupts pending */

#define UART_IIR_ID        0x06        /* Mask for the interrupt ID */

#define UART_IIR_MSI        0x00        /* Modem status interrupt */

#define UART_IIR_THRI        0x02        /* Transmitter holding register empty */

#define UART_IIR_RDI        0x04        /* Receiver data interrupt */

#define UART_IIR_RLSI        0x06        /* Receiver line status interrupt */

/*

 * These are the definitions for the Modem Control Register

 */

#define UART_MCR_LOOP        0x10        /* Enable loopback test mode */

#define UART_MCR_OUT2        0x08        /* Out2 complement */

#define UART_MCR_OUT1        0x04        /* Out1 complement */

#define UART_MCR_RTS        0x02        /* RTS complement */

#define UART_MCR_DTR        0x01        /* DTR complement */

/*

 * These are the definitions for the Modem Status Register

 */

#define UART_MSR_DCD        0x80        /* Data Carrier Detect */

#define UART_MSR_RI        0x40        /* Ring Indicator */

#define UART_MSR_DSR        0x20        /* Data Set Ready */

#define UART_MSR_CTS        0x10        /* Clear to Send */

#define UART_MSR_DDCD        0x08        /* Delta DCD */

#define UART_MSR_TERI        0x04        /* Trailing edge ring indicator */

#define UART_MSR_DDSR        0x02        /* Delta DSR */

#define UART_MSR_DCTS        0x01        /* Delta CTS */

#define UART_MSR_ANY_DELTA 0x0F        /* Any of the delta bits! */

#define UART_LSR_TEMT        0x40        /* Transmitter empty */

#define UART_LSR_THRE        0x20        /* Transmit-hold-register empty */

#define UART_LSR_BI        0x10        /* Break interrupt indicator */

#define UART_LSR_FE        0x08        /* Frame error indicator */

#define UART_LSR_PE        0x04        /* Parity error indicator */

#define UART_LSR_OE        0x02        /* Overrun error indicator */

#define UART_LSR_DR        0x01        /* Receiver data ready */

struct SerialState {

    uint8_t divider;

    uint8_t rbr; /* receive register */

    uint8_t ier;

    uint8_t iir; /* read only */

    uint8_t lcr;

    uint8_t mcr;

    uint8_t lsr; /* read only */

    uint8_t msr;

    uint8_t scr;

    /* NOTE: this hidden state is necessary for tx irq generation as

       it can be reset while reading iir */

    int thr_ipending;

    int irq;

    CharDriverState *chr;

};

static void serial_update_irq(SerialState *s)

{

    if ((s->lsr & UART_LSR_DR) && (s->ier & UART_IER_RDI)) {

        s->iir = UART_IIR_RDI;

    } else if (s->thr_ipending && (s->ier & UART_IER_THRI)) {

        s->iir = UART_IIR_THRI;

    } else {

        s->iir = UART_IIR_NO_INT;

    }

    if (s->iir != UART_IIR_NO_INT) {

        pic_set_irq(s->irq, 1);

    } else {

        pic_set_irq(s->irq, 0);

    }

}

static void serial_ioport_write(void *opaque, uint32_t addr, uint32_t val)

{

    SerialState *s = opaque;

    unsigned char ch;

    addr &= 7;

#ifdef DEBUG_SERIAL

    printf("serial: write addr=0x%02x val=0x%02x\n", addr, val);

#endif

    switch(addr) {

    default:

    case 0:

        if (s->lcr & UART_LCR_DLAB) {

            s->divider = (s->divider & 0xff00) | val;

        } else {

            s->thr_ipending = 0;

            s->lsr &= ~UART_LSR_THRE;

            serial_update_irq(s);

            ch = val;

            qemu_chr_write(s->chr, &ch, 1);

            s->thr_ipending = 1;

            s->lsr |= UART_LSR_THRE;

            s->lsr |= UART_LSR_TEMT;

            serial_update_irq(s);

        }

        break;

    case 1:

        if (s->lcr & UART_LCR_DLAB) {

            s->divider = (s->divider & 0x00ff) | (val << 8);

        } else {

            s->ier = val;

            serial_update_irq(s);

        }

        break;

    case 2:

        break;

    case 3:

        s->lcr = val;

        break;

    case 4:

        s->mcr = val;

        break;

    case 5:

        break;

    case 6:

        s->msr = val;

        break;

    case 7:

        s->scr = val;

        break;

    }

}

static uint32_t serial_ioport_read(void *opaque, uint32_t addr)

{

    SerialState *s = opaque;

    uint32_t ret;

    addr &= 7;

    switch(addr) {

    default:

    case 0:

        if (s->lcr & UART_LCR_DLAB) {

            ret = s->divider & 0xff; 

        } else {

            ret = s->rbr;

            s->lsr &= ~(UART_LSR_DR | UART_LSR_BI);

            serial_update_irq(s);

        }

        break;

    case 1:

        if (s->lcr & UART_LCR_DLAB) {

            ret = (s->divider >> 8) & 0xff;

        } else {

            ret = s->ier;

        }

        break;

    case 2:

        ret = s->iir;

        /* reset THR pending bit */

        if ((ret & 0x7) == UART_IIR_THRI)

            s->thr_ipending = 0;

        serial_update_irq(s);

        break;

    case 3:

        ret = s->lcr;

        break;

    case 4:

        ret = s->mcr;

        break;

    case 5:

        ret = s->lsr;

        break;

    case 6:

        if (s->mcr & UART_MCR_LOOP) {

            /* in loopback, the modem output pins are connected to the

               inputs */

            ret = (s->mcr & 0x0c) << 4;

            ret |= (s->mcr & 0x02) << 3;

            ret |= (s->mcr & 0x01) << 5;

        } else {

            ret = s->msr;

        }

        break;

    case 7:

        ret = s->scr;

        break;

    }

#ifdef DEBUG_SERIAL

    printf("serial: read addr=0x%02x val=0x%02x\n", addr, ret);

#endif

    return ret;

}

static int serial_can_receive(SerialState *s)

{

    return !(s->lsr & UART_LSR_DR);

}

static void serial_receive_byte(SerialState *s, int ch)

{

    s->rbr = ch;

    s->lsr |= UART_LSR_DR;

    serial_update_irq(s);

}

static void serial_receive_break(SerialState *s)

{

    s->rbr = 0;

    s->lsr |= UART_LSR_BI | UART_LSR_DR;

    serial_update_irq(s);

}

static int serial_can_receive1(void *opaque)

{

    SerialState *s = opaque;

    return serial_can_receive(s);

}

static void serial_receive1(void *opaque, const uint8_t *buf, int size)

{

    SerialState *s = opaque;

    serial_receive_byte(s, buf[0]);

}

static void serial_event(void *opaque, int event)

{

    SerialState *s = opaque;

    if (event == CHR_EVENT_BREAK)

        serial_receive_break(s);

}

/* If fd is zero, it means that the serial device uses the console */

SerialState *serial_init(int base, int irq, CharDriverState *chr)

{

    SerialState *s;

    s = qemu_mallocz(sizeof(SerialState));

    if (!s)

        return NULL;

    s->irq = irq;

    s->lsr = UART_LSR_TEMT | UART_LSR_THRE;

    s->iir = UART_IIR_NO_INT;

    register_ioport_write(base, 8, 1, serial_ioport_write, s);

    register_ioport_read(base, 8, 1, serial_ioport_read, s);

    s->chr = chr;

    qemu_chr_add_read_handler(chr, serial_can_receive1, serial_receive1, s);

    qemu_chr_add_event_handler(chr, serial_event);

    return s;

}