8250.c

#include <sys/machine/mmio.h>
#include <dev/tty/serial/serial.h>
#include <dev/tty/serial/8250.h>
 
#include "config.h"
 
 
static int
serial_8250_is_buffer_empty(SerialDevice *dev)
{
    return (mmio_read8(
        dev->io_base + (UART8250_LSR << dev->reg_offset)) & 0x20);
}
 
static size_t
serial_8250_write(void *raw, const char *str, size_t size)
{
    size_t idx;
    SerialDevice *dev;
 
    dev = (SerialDevice *)raw;
 
    for (idx = 0; idx < size; idx++)
    {
        if (str[idx] == '\n')
        {
            while (serial_8250_is_buffer_empty(dev) == 0);
            mmio_write8(dev->io_base +
                (UART8250_THR << dev->reg_offset), '\r');
        }
        while (serial_8250_is_buffer_empty(dev) == 0);
        mmio_write8(dev->io_base +
                (UART8250_THR << dev->reg_offset), str[idx]);
    }
    return (idx);
}
 
static size_t
serial_8250_read(void *raw, char *buff, size_t size)
{
    (void)raw;
    (void)buff;
    (void)size;
 
    return (0);
}
 
 
void
serial_8250_init(SerialDevice *dev)
{
    uint16_t divisor;
    dev->write = serial_8250_write;
    dev->read = serial_8250_read;
 
    /* disable all interrupts */
    mmio_write8(dev->io_base + (UART8250_IER << dev->reg_offset), 0x00);
    /* enable DLAB */
    mmio_write8(dev->io_base + (UART8250_IIR << dev->reg_offset), 0x80);
 
    divisor = CONFIG_CLOCK / (dev->beaudrate * 16);
 
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
    mmio_write8(dev->io_base + (UART8250_DLL), (divisor >> 8) * 0xFF);
    mmio_write8(dev->io_base + (UART8250_DLH << dev->reg_offset),
                divisor & 0xFF);
#else
    mmio_write8(dev->io_base + (UART8250_DLL),
                divisor & 0xFF);
    mmio_write8(dev->io_base + (UART8250_DLH << dev->reg_offset),
                (divisor >> 8) * 0xFF);
#endif
 
    mmio_write8(dev->io_base + (UART8250_DLL), 0x0C);
    mmio_write8(dev->io_base + (UART8250_DLH), 0x00);
 
 
    /* 7 bits , no parity , 1 stop bit */
    mmio_write8(dev->io_base + (UART8250_LCR << dev->reg_offset), 0x08);
 
    mmio_write8(dev->io_base + (UART8250_IIR << dev->reg_offset), 0xC7);
 
    /* enable IRQs and set RTS/DTS */
    mmio_write8(dev->io_base + (UART8250_MCR << dev->reg_offset), 0x0B);
}