xnu-3789.41.3.tar.gz

[apple/xnu.git] / pexpert / i386 / pe_serial.c

/*
 * Copyright (c) 2000-2006 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 * 
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 * 
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 * 
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 * 
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */

/*
 * file: pe_serial.c
 *       Polled-mode 16x50 UART driver.
 */

#include <pexpert/protos.h>
#include <pexpert/pexpert.h>

/* standard port addresses */
enum {
    COM1_PORT_ADDR = 0x3f8,
    COM2_PORT_ADDR = 0x2f8
};

/* UART register offsets */
enum {
    UART_RBR = 0,  /* receive buffer Register   (R) */
    UART_THR = 0,  /* transmit holding register (W) */
    UART_DLL = 0,  /* DLAB = 1, divisor latch (LSB) */
    UART_IER = 1,  /* interrupt enable register     */
    UART_DLM = 1,  /* DLAB = 1, divisor latch (MSB) */
    UART_IIR = 2,  /* interrupt ident register (R)  */
    UART_FCR = 2,  /* fifo control register (W)     */
    UART_LCR = 3,  /* line control register         */
    UART_MCR = 4,  /* modem control register        */
    UART_LSR = 5,  /* line status register          */
    UART_MSR = 6,  /* modem status register         */
    UART_SCR = 7   /* scratch register              */
};

enum {
    UART_LCR_8BITS = 0x03,
    UART_LCR_DLAB  = 0x80
};

enum {
    UART_MCR_DTR   = 0x01,
    UART_MCR_RTS   = 0x02,
    UART_MCR_OUT1  = 0x04,
    UART_MCR_OUT2  = 0x08,
    UART_MCR_LOOP  = 0x10
};

enum {
    UART_LSR_DR    = 0x01,
    UART_LSR_OE    = 0x02,
    UART_LSR_PE    = 0x04,
    UART_LSR_FE    = 0x08,
    UART_LSR_THRE  = 0x20
};

static unsigned uart_baud_rate = 115200;
#define UART_PORT_ADDR  COM1_PORT_ADDR

#define UART_CLOCK  1843200   /* 1.8432 MHz clock */

#define WRITE(r, v)  outb(UART_PORT_ADDR + UART_##r, v)
#define READ(r)      inb(UART_PORT_ADDR + UART_##r)
#define DELAY(x)     { volatile int _d_; for (_d_ = 0; _d_ < (10000*x); _d_++) ; }

static int uart_initted = 0;   /* 1 if init'ed */

static int
uart_probe( void )
{
    /* Verify that the Scratch Register is accessible */

    WRITE( SCR, 0x5a );
    if (READ(SCR) != 0x5a) return 0;
    WRITE( SCR, 0xa5 );
    if (READ(SCR) != 0xa5) return 0;
    return 1;
}

static void
uart_set_baud_rate( unsigned long baud_rate )
{
    const unsigned char lcr = READ( LCR );
    unsigned long       div;

    if (baud_rate == 0) baud_rate = 9600;
    div = UART_CLOCK / 16 / baud_rate;
    WRITE( LCR, lcr | UART_LCR_DLAB );
    WRITE( DLM, (unsigned char)(div >> 8) );
    WRITE( DLL, (unsigned char) div );
    WRITE( LCR, lcr & ~UART_LCR_DLAB);
}

static void
uart_putc( char c )
{
    if (!uart_initted) return;

    /* Wait for THR empty */
    while ( !(READ(LSR) & UART_LSR_THRE) ) DELAY(1);

    WRITE( THR, c );
}

static int
uart_getc( void )
{
    /*
     * This function returns:
     * -1 : no data
     * -2 : receiver error
     * >0 : character received
     */

    unsigned char lsr;

    if (!uart_initted) return -1;

    lsr = READ( LSR );

    if ( lsr & (UART_LSR_FE | UART_LSR_PE | UART_LSR_OE) )
    {
        READ( RBR ); /* discard */
        return -2;
    }

    if ( lsr & UART_LSR_DR )
    {
        return READ( RBR );
    }

    return -1;
}

int serial_init( void )
{
    unsigned serial_baud_rate = 0;
	
    if ( uart_probe() == 0 ) return 0;

    /* Disable hardware interrupts */

    WRITE( MCR, 0 );
    WRITE( IER, 0 );

    /* Disable FIFO's for 16550 devices */

    WRITE( FCR, 0 );

    /* Set for 8-bit, no parity, DLAB bit cleared */

    WRITE( LCR, UART_LCR_8BITS );

    /* Set baud rate - use the supplied boot-arg if available */

    if (PE_parse_boot_argn("serialbaud", &serial_baud_rate, sizeof (serial_baud_rate)))
    {
	    /* Valid divisor? */
	    if (!((UART_CLOCK / 16) % serial_baud_rate)) {
		    uart_baud_rate = serial_baud_rate;
	    }
    }
    uart_set_baud_rate( uart_baud_rate );

    /* Assert DTR# and RTS# lines (OUT2?) */

    WRITE( MCR, UART_MCR_DTR | UART_MCR_RTS );

    /* Clear any garbage in the input buffer */

    READ( RBR );

    uart_initted = 1;

    return 1;
}

void serial_putc( char c )
{
    uart_putc(c);
}

int serial_getc( void )
{
    return uart_getc();
}