Archipelago » qemu

/*

 *  QEMU model of the Milkymist UART block.

 *

 *  Copyright (c) 2010 Michael Walle <michael@walle.cc>

 *

 * This library is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public

 * License as published by the Free Software Foundation; either

 * version 2 of the License, or (at your option) any later version.

 *

 * This library is distributed in the hope that it will be useful,

 * but WITHOUT ANY WARRANTY; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with this library; if not, see <http://www.gnu.org/licenses/>.

 *

 *

 * Specification available at:

 *   http://www.milkymist.org/socdoc/uart.pdf

 */

#include "hw.h"

#include "sysbus.h"

#include "trace.h"

#include "qemu-char.h"

#include "qemu-error.h"

enum {

    R_RXTX = 0,

    R_DIV,

    R_STAT,

    R_CTRL,

    R_DBG,

    R_MAX

};

enum {

    STAT_THRE   = (1<<0),

    STAT_RX_EVT = (1<<1),

    STAT_TX_EVT = (1<<2),

};

enum {

    CTRL_RX_IRQ_EN = (1<<0),

    CTRL_TX_IRQ_EN = (1<<1),

    CTRL_THRU_EN   = (1<<2),

};

enum {

    DBG_BREAK_EN = (1<<0),

};

struct MilkymistUartState {

    SysBusDevice busdev;

    MemoryRegion regs_region;

    CharDriverState *chr;

    qemu_irq irq;

    uint32_t regs[R_MAX];

};

typedef struct MilkymistUartState MilkymistUartState;

static void uart_update_irq(MilkymistUartState *s)

{

    int rx_event = s->regs[R_STAT] & STAT_RX_EVT;

    int tx_event = s->regs[R_STAT] & STAT_TX_EVT;

    int rx_irq_en = s->regs[R_CTRL] & CTRL_RX_IRQ_EN;

    int tx_irq_en = s->regs[R_CTRL] & CTRL_TX_IRQ_EN;

    if ((rx_irq_en && rx_event) || (tx_irq_en && tx_event)) {

        trace_milkymist_uart_raise_irq();

        qemu_irq_raise(s->irq);

    } else {

        trace_milkymist_uart_lower_irq();

        qemu_irq_lower(s->irq);

    }

}

static uint64_t uart_read(void *opaque, target_phys_addr_t addr,

                          unsigned size)

{

    MilkymistUartState *s = opaque;

    uint32_t r = 0;

    addr >>= 2;

    switch (addr) {

    case R_RXTX:

        r = s->regs[addr];

        break;

    case R_DIV:

    case R_STAT:

    case R_CTRL:

    case R_DBG:

        r = s->regs[addr];

        break;

    default:

        error_report("milkymist_uart: read access to unknown register 0x"

                TARGET_FMT_plx, addr << 2);

        break;

    }

    trace_milkymist_uart_memory_read(addr << 2, r);

    return r;

}

static void uart_write(void *opaque, target_phys_addr_t addr, uint64_t value,

                       unsigned size)

{

    MilkymistUartState *s = opaque;

    unsigned char ch = value;

    trace_milkymist_uart_memory_write(addr, value);

    addr >>= 2;

    switch (addr) {

    case R_RXTX:

        if (s->chr) {

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

        }

        s->regs[R_STAT] |= STAT_TX_EVT;

        break;

    case R_DIV:

    case R_CTRL:

    case R_DBG:

        s->regs[addr] = value;

        break;

    case R_STAT:

        /* write one to clear bits */

        s->regs[addr] &= ~(value & (STAT_RX_EVT | STAT_TX_EVT));

        break;

    default:

        error_report("milkymist_uart: write access to unknown register 0x"

                TARGET_FMT_plx, addr << 2);

        break;

    }

    uart_update_irq(s);

}

static const MemoryRegionOps uart_mmio_ops = {

    .read = uart_read,

    .write = uart_write,

    .valid = {

        .min_access_size = 4,

        .max_access_size = 4,

    },

    .endianness = DEVICE_NATIVE_ENDIAN,

};

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

{

    MilkymistUartState *s = opaque;

    assert(!(s->regs[R_STAT] & STAT_RX_EVT));

    s->regs[R_STAT] |= STAT_RX_EVT;

    s->regs[R_RXTX] = *buf;

    uart_update_irq(s);

}

static int uart_can_rx(void *opaque)

{

    MilkymistUartState *s = opaque;

    return !(s->regs[R_STAT] & STAT_RX_EVT);

}

static void uart_event(void *opaque, int event)

{

}

static void milkymist_uart_reset(DeviceState *d)

{

    MilkymistUartState *s = container_of(d, MilkymistUartState, busdev.qdev);

    int i;

    for (i = 0; i < R_MAX; i++) {

        s->regs[i] = 0;

    }

    /* THRE is always set */

    s->regs[R_STAT] = STAT_THRE;

}

static int milkymist_uart_init(SysBusDevice *dev)

{

    MilkymistUartState *s = FROM_SYSBUS(typeof(*s), dev);

    sysbus_init_irq(dev, &s->irq);

    memory_region_init_io(&s->regs_region, &uart_mmio_ops, s,

            "milkymist-uart", R_MAX * 4);

    sysbus_init_mmio_region(dev, &s->regs_region);

    s->chr = qdev_init_chardev(&dev->qdev);

    if (s->chr) {

        qemu_chr_add_handlers(s->chr, uart_can_rx, uart_rx, uart_event, s);

    }

    return 0;

}

static const VMStateDescription vmstate_milkymist_uart = {

    .name = "milkymist-uart",

    .version_id = 1,

    .minimum_version_id = 1,

    .minimum_version_id_old = 1,

    .fields      = (VMStateField[]) {

        VMSTATE_UINT32_ARRAY(regs, MilkymistUartState, R_MAX),

        VMSTATE_END_OF_LIST()

    }

};

static SysBusDeviceInfo milkymist_uart_info = {

    .init = milkymist_uart_init,

    .qdev.name  = "milkymist-uart",

    .qdev.size  = sizeof(MilkymistUartState),

    .qdev.vmsd  = &vmstate_milkymist_uart,

    .qdev.reset = milkymist_uart_reset,

};

static void milkymist_uart_register(void)

{

    sysbus_register_withprop(&milkymist_uart_info);

}

device_init(milkymist_uart_register)