lk/platform/pc/uart.c

/*
 * Copyright (c) 2012 Corey Tabaka
 *
 * Use of this source code is governed by a MIT-style
 * license that can be found in the LICENSE file or at
 * https://opensource.org/licenses/MIT
 */

#include <dev/driver.h>
#include <dev/class/uart.h>
#include <lk/debug.h>
#include <assert.h>
#include <malloc.h>
#include <lk/err.h>
#include <lib/cbuf.h>
#include <platform/uart.h>
#include <arch/x86.h>
#include <kernel/thread.h>
#include <platform/interrupts.h>

struct device_class uart_device_class = {
    .name = "uart",
};

struct uart_driver_state {
    struct cbuf rx_buf;
    struct cbuf tx_buf;
};

static status_t uart_init(struct device *dev);

static enum handler_return uart_irq_handler(void *arg);
static int uart_write_thread(void *arg);

static ssize_t uart_read(struct device *dev, void *buf, size_t len);
static ssize_t uart_write(struct device *dev, const void *buf, size_t len);

static struct uart_ops the_ops = {
    .std = {
        .device_class = &uart_device_class,
        .init = uart_init,
    },
    .read = uart_read,
    .write = uart_write,
};

DRIVER_EXPORT(uart, &the_ops.std);

static status_t uart_init(struct device *dev) {
    status_t res = NO_ERROR;

    if (!dev)
        return ERR_INVALID_ARGS;

    if (!dev->config)
        return ERR_NOT_CONFIGURED;

    const struct platform_uart_config *config = dev->config;

    struct uart_driver_state *state = malloc(sizeof(struct uart_driver_state));
    if (!state) {
        res = ERR_NO_MEMORY;
        goto done;
    }

    dev->state = state;

    /* set up the driver state */
    cbuf_initialize(&state->rx_buf, config->rx_buf_len);
    cbuf_initialize(&state->tx_buf, config->tx_buf_len);

    /* configure the uart */
    int divisor = 115200 / config->baud_rate;

    outp(config->io_port + 3, 0x80); // set up to load divisor latch
    outp(config->io_port + 0, divisor & 0xff); // lsb
    outp(config->io_port + 1, divisor >> 8); // msb
    outp(config->io_port + 3, 3); // 8N1
    outp(config->io_port + 2, 0x07); // enable FIFO, clear, 14-byte threshold

    register_int_handler(config->irq, uart_irq_handler, dev);
    unmask_interrupt(config->irq);

    //outp(config->io_port + 1, 0x3); // enable rx data available and tx holding empty interrupts
    outp(config->io_port + 1, 0x1); // enable rx data available interrupts

    thread_resume(thread_create("[uart writer]", uart_write_thread, dev, DEFAULT_PRIORITY,
                                DEFAULT_STACK_SIZE));

done:
    return res;
}

static enum handler_return uart_irq_handler(void *arg) {
    bool resched = false;
    struct device *dev = arg;

    DEBUG_ASSERT(dev);
    DEBUG_ASSERT(dev->config);
    DEBUG_ASSERT(dev->state);

    const struct platform_uart_config *config = dev->config;
    struct uart_driver_state *state = dev->state;

    while (inp(config->io_port + 5) & (1<<0)) {
        char c = inp(config->io_port + 0);
        cbuf_write(&state->rx_buf, &c, 1, false);
        resched = true;
    }

    return resched ? INT_RESCHEDULE : INT_NO_RESCHEDULE;
}

static int uart_write_thread(void *arg) {
    struct device *dev = arg;

    DEBUG_ASSERT(dev);
    DEBUG_ASSERT(dev->config);
    DEBUG_ASSERT(dev->state);

    const struct platform_uart_config *config = dev->config;
    struct uart_driver_state *state = dev->state;

    return 0;

    while (true) {
        char c = cbuf_read(&state->tx_buf, &c, 1, true);

        while ((inp(config->io_port + 5) & (1<<6)) == 0)
            ;

        outp(config->io_port + 0, c);
    }

    return 0;
}

static ssize_t uart_read(struct device *dev, void *buf, size_t len) {
    if (!dev || !buf)
        return ERR_INVALID_ARGS;

    DEBUG_ASSERT(dev->state);
    struct uart_driver_state *state = dev->state;

    return cbuf_read(&state->rx_buf, buf, len, true);
}

static ssize_t uart_write(struct device *dev, const void *buf, size_t len) {
    if (!dev || !buf)
        return ERR_INVALID_ARGS;

    DEBUG_ASSERT(dev->state);
    struct uart_driver_state *state = dev->state;

    return cbuf_write(&state->tx_buf, buf, len, true);
}