sys/boot/i386/boot2/sio.S

   1 #
   2 # Copyright (c) 1998 Robert Nordier
   3 # All rights reserved.
   4 #
   5 # Redistribution and use in source and binary forms are freely
   6 # permitted provided that the above copyright notice and this
   7 # paragraph and the following disclaimer are duplicated in all
   8 # such forms.
   9 #
  10 # This software is provided "AS IS" and without any express or
  11 # implied warranties, including, without limitation, the implied
  12 # warranties of merchantability and fitness for a particular
  13 # purpose.
  14 #
  15
  16 # $FreeBSD: src/sys/boot/i386/boot2/sio.s,v 1.4 1999/08/28 00:40:02 peter Exp $
  17
  18                 .set SIO_PRT,SIOPRT             # Base port
  19                 .set SIO_FMT,SIOFMT             # 8N1
  20                 .set SIO_DIV,(115200/SIOSPD)    # 115200 / SPD
  21
  22                 .globl sio_init
  23                 .globl sio_flush
  24                 .globl sio_putc
  25                 .globl sio_getc
  26                 .globl sio_ischar
  27
  28 # void sio_init(void)
  29
  30 sio_init:       movw $SIO_PRT+0x3,%dx           # Data format reg
  31                 movb $SIO_FMT|0x80,%al          # Set format
  32                 outb %al,(%dx)                  #  and DLAB
  33                 pushl %edx                      # Save
  34                 subb $0x3,%dl                   # Divisor latch reg
  35                 movw $SIO_DIV,%ax               # Set
  36                 outw %ax,(%dx)                  #  BPS
  37                 popl %edx                       # Restore
  38                 movb $SIO_FMT,%al               # Clear
  39                 outb %al,(%dx)                  #  DLAB
  40                 incl %edx                       # Modem control reg
  41                 movb $0x3,%al                   # Set RTS,
  42                 outb %al,(%dx)                  #  DTR
  43                 incl %edx                       # Line status reg
  44
  45 # void sio_flush(void)
  46
  47 sio_flush.0:    call sio_getc.1                 # Get character
  48 sio_flush:      call sio_ischar                 # Check for character
  49                 jnz sio_flush.0                 # Till none
  50                 ret                             # To caller
  51
  52 # void sio_putc(int c)
  53
  54 sio_putc:       movw $SIO_PRT+0x5,%dx           # Line status reg
  55                 xor %ecx,%ecx                   # Timeout
  56                 movb $0x40,%ch                  #  counter
  57 sio_putc.1:     inb (%dx),%al                   # Transmitter
  58                 testb $0x20,%al                 #  buffer empty?
  59                 loopz sio_putc.1                # No
  60                 jz sio_putc.2                   # If timeout
  61                 movb 0x4(%esp,1),%al            # Get character
  62                 subb $0x5,%dl                   # Transmitter hold reg
  63                 outb %al,(%dx)                  # Write character
  64 sio_putc.2:     ret $0x4                        # To caller
  65
  66 # int sio_getc(void)
  67
  68 sio_getc:       call sio_ischar                 # Character available?
  69                 jz sio_getc                     # No
  70 sio_getc.1:     subb $0x5,%dl                   # Receiver buffer reg
  71                 inb (%dx),%al                   # Read character
  72                 ret                             # To caller
  73
  74 # int sio_ischar(void)
  75
  76 sio_ischar:     movw $SIO_PRT+0x5,%dx           # Line status register
  77                 xorl %eax,%eax                  # Zero
  78                 inb (%dx),%al                   # Received data
  79                 andb $0x1,%al                   #  ready?
  80                 ret                             # To caller