x86_uart.c

/*
 * Copyright (C) 2014  René Kijewski  <rene.kijewski@fu-berlin.de>
 *
 * 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 2.1 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, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
 */

/**
 * @ingroup     x86-irq
 * @{
 *
 * @file
 * @brief       UART reading and writing.
 *
 * @author      René Kijewski <rene.kijewski@fu-berlin.de>
 *
 * @}
 */

#include "board.h"
#include "x86_ports.h"
#include "x86_uart.h"

#include <cpu.h>
#include <board_uart0.h>

#include <inttypes.h>
#include <stdint.h>
#include <stdio.h>

void x86_early_init_uart(void)
{
    outb(UART_PORT + IER, 0x00); /* Disable all interrupts */

    outb(UART_PORT + LCR, LCR_DLAB);
    outb(UART_PORT + DLL, BAUD_LL); /* Set divisor (lo byte) */
    outb(UART_PORT + DLH, BAUD_HL); /*             (hi byte) */
    outb(UART_PORT + LCR, LCR_WORD_BITS_8 | LCR_PAR_NONE | LCR_STOP_BITS_1);
    outb(UART_PORT + FCR, FCR_ENABLE | FCR_CLR_RECV | FCR_CLR_SEND | FCR_TRIGGER_16);
    outb(UART_PORT + MCR, MCR_DSR | MCR_RTS | MCR_AUX2);
}

static bool is_output_empty(void)
{
    uint8_t data = inb(UART_PORT + LSR);
    return (data & 0x20) != 0;
}

static bool is_input_empty(void)
{
    uint8_t data = inb(UART_PORT + LSR);
    return (data & 0x01) == 0;
}

ssize_t x86_uart_write(const char *buf, size_t len)
{
    if (!UART_PORT) {
        return -1;
    }
    (void) buf;

    size_t written = 0;
    while (written < len) {
        while (!is_output_empty()) {
            asm volatile ("pause");
        }
        outb(UART_PORT + THR, buf[written]);
        ++written;
    }
    return written;
}

ssize_t x86_uart_read(char *buf, size_t len)
{
    if (!UART_PORT) {
        return -1;
    }

    size_t read = 0;
    while (read < len) {
        while (!is_input_empty()) {
            asm volatile ("pause");
        }
        buf[read] = inb(UART_PORT + RBR);
        ++read;
    }
    return read;
}

#ifdef MODULE_UART0
static void com_handler(uint8_t irq_num)
{
    (void) irq_num; /* == UART_IRQ */
    switch (inb(UART_PORT + IIR) & IIR_INT_MASK) {
        case IIR_INT_BR: {
            while (is_input_empty()) {
                asm volatile ("pause");
            }
            do {
                uint8_t c = inb(UART_PORT + RBR);
                uart0_handle_incoming(c);
            } while (!is_input_empty());
            uart0_notify_thread();
            break;
        }
        case IIR_INT_TH:
        case IIR_INT_LS:
        case IIR_INT_TO:
        default:
            break;
    }
}
#endif /* ifdef MODULE_UART0 */

void x86_init_uart(void)
{
#ifdef MODULE_UART0
    x86_pic_set_handler(UART_IRQ, com_handler);
    x86_pic_enable_irq(UART_IRQ);

    outb(UART_PORT + IER, IER_RECV); /* Enable receive interrupt */

    puts("UART initialized");
#endif
}