legacy.c

Go to the documentation of this file.

/*
 * COPYRIGHT:       See COPYING in the top level directory
 * PROJECT:         Serial port driver
 * FILE:            drivers/bus/serial/legacy.c
 * PURPOSE:         Legacy serial port enumeration
 *
 * PROGRAMMERS:     Hervé Poussineau (hpoussin@reactos.org)
 *                  Mark Junker (mjscod@gmx.de)
 */
 
#include "serial.h"
 
#include <debug.h>
 
UART_TYPE
SerialDetectUartType(
    IN PUCHAR BaseAddress)
{
    UCHAR Lcr, TestLcr;
    UCHAR OldScr, Scr5A, ScrA5;
    BOOLEAN FifoEnabled;
    UCHAR NewFifoStatus;
 
    Lcr = READ_PORT_UCHAR(SER_LCR(BaseAddress));
    WRITE_PORT_UCHAR(SER_LCR(BaseAddress), Lcr ^ 0xFF);
    TestLcr = READ_PORT_UCHAR(SER_LCR(BaseAddress)) ^ 0xFF;
    WRITE_PORT_UCHAR(SER_LCR(BaseAddress), Lcr);
 
    /* Accessing the LCR must work for a usable serial port */
    if (TestLcr != Lcr)
        return UartUnknown;
 
    /* Ensure that all following accesses are done as required */
    READ_PORT_UCHAR(SER_RBR(BaseAddress));
    READ_PORT_UCHAR(SER_IER(BaseAddress));
    READ_PORT_UCHAR(SER_IIR(BaseAddress));
    READ_PORT_UCHAR(SER_LCR(BaseAddress));
    READ_PORT_UCHAR(SER_MCR(BaseAddress));
    READ_PORT_UCHAR(SER_LSR(BaseAddress));
    READ_PORT_UCHAR(SER_MSR(BaseAddress));
    READ_PORT_UCHAR(SER_SCR(BaseAddress));
 
    /* Test scratch pad */
    OldScr = READ_PORT_UCHAR(SER_SCR(BaseAddress));
    WRITE_PORT_UCHAR(SER_SCR(BaseAddress), 0x5A);
    Scr5A = READ_PORT_UCHAR(SER_SCR(BaseAddress));
    WRITE_PORT_UCHAR(SER_SCR(BaseAddress), 0xA5);
    ScrA5 = READ_PORT_UCHAR(SER_SCR(BaseAddress));
    WRITE_PORT_UCHAR(SER_SCR(BaseAddress), OldScr);
 
    /* When non-functional, we have a 8250 */
    if (Scr5A != 0x5A || ScrA5 != 0xA5)
        return Uart8250;
 
    /* Test FIFO type */
    FifoEnabled = (READ_PORT_UCHAR(SER_IIR(BaseAddress)) & 0x80) != 0;
    WRITE_PORT_UCHAR(SER_FCR(BaseAddress), SR_FCR_ENABLE_FIFO);
    NewFifoStatus = READ_PORT_UCHAR(SER_IIR(BaseAddress)) & 0xC0;
    if (!FifoEnabled)
        WRITE_PORT_UCHAR(SER_FCR(BaseAddress), 0);
    switch (NewFifoStatus)
    {
        case 0x00:
            return Uart16450;
        case 0x40:
        case 0x80:
            /* Not sure about this but the documentation says that 0x40
             * indicates an unusable FIFO but my tests only worked
             * with 0x80 */
            return Uart16550;
    }
 
    /* FIFO is only functional for 16550A+ */
    return Uart16550A;
}