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/*
* Copyright (c) 1998 Robert Nordier
* All rights reserved.
*
* Redistribution and use in source and binary forms are freely
* permitted provided that the above copyright notice and this
* paragraph and the following disclaimer are duplicated in all
* such forms.
*
* This software is provided "AS IS" and without any express or
* implied warranties, including, without limitation, the implied
* warranties of merchantability and fitness for a particular
* purpose.
*
* $FreeBSD: src/sys/boot/i386/boot2/sio.S,v 1.10.8.1 2009/04/15 03:14:26 kensmith Exp $
*/
.set SIO_PRT,SIOPRT # Base port
.set SIO_FMT,SIOFMT # 8N1
.globl sio_init
.globl sio_flush
.globl sio_putc
.globl sio_getc
.globl sio_ischar
/* void sio_init(int div) */
sio_init: movw $SIO_PRT+0x3,%dx # Data format reg
movb $SIO_FMT|0x80,%al # Set format
outb %al,(%dx) # and DLAB
pushl %edx # Save
subb $0x3,%dl # Divisor latch reg
movl 0x8(%esp),%eax # Set
outw %ax,(%dx) # BPS
popl %edx # Restore
movb $SIO_FMT,%al # Clear
outb %al,(%dx) # DLAB
incl %edx # Modem control reg
movb $0x3,%al # Set RTS,
outb %al,(%dx) # DTR
incl %edx # Line status reg
call sio_flush
ret $0x4
/* void sio_flush(void) */
sio_flush.0: call sio_getc.1 # Get character
sio_flush: call sio_ischar # Check for character
jnz sio_flush.0 # Till none
ret # To caller
/* void sio_putc(int c) */
sio_putc: movw $SIO_PRT+0x5,%dx # Line status reg
xor %ecx,%ecx # Timeout
movb $0x40,%ch # counter
sio_putc.1: inb (%dx),%al # Transmitter
testb $0x20,%al # buffer empty?
loopz sio_putc.1 # No
jz sio_putc.2 # If timeout
movb 0x4(%esp,1),%al # Get character
subb $0x5,%dl # Transmitter hold reg
outb %al,(%dx) # Write character
sio_putc.2: ret $0x4 # To caller
/* int sio_getc(void) */
sio_getc: call sio_ischar # Character available?
jz sio_getc # No
sio_getc.1: subb $0x5,%dl # Receiver buffer reg
inb (%dx),%al # Read character
ret # To caller
/* int sio_ischar(void) */
sio_ischar: movw $SIO_PRT+0x5,%dx # Line status register
xorl %eax,%eax # Zero
inb (%dx),%al # Received data
andb $0x1,%al # ready?
ret # To caller
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