pexpert/i386/pe_serial.c

   1 /*
   2  * Copyright (c) 2000-2006 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28
  29 /*
  30  * file: pe_serial.c
  31  *       Polled-mode 16x50 UART driver.
  32  */
  33
  34 #include <pexpert/protos.h>
  35 #include <pexpert/pexpert.h>
  36
  37 /* standard port addresses */
  38 enum {
  39     COM1_PORT_ADDR = 0x3f8,
  40     COM2_PORT_ADDR = 0x2f8
  41 };
  42
  43 /* UART register offsets */
  44 enum {
  45     UART_RBR = 0,  /* receive buffer Register   (R) */
  46     UART_THR = 0,  /* transmit holding register (W) */
  47     UART_DLL = 0,  /* DLAB = 1, divisor latch (LSB) */
  48     UART_IER = 1,  /* interrupt enable register     */
  49     UART_DLM = 1,  /* DLAB = 1, divisor latch (MSB) */
  50     UART_IIR = 2,  /* interrupt ident register (R)  */
  51     UART_FCR = 2,  /* fifo control register (W)     */
  52     UART_LCR = 3,  /* line control register         */
  53     UART_MCR = 4,  /* modem control register        */
  54     UART_LSR = 5,  /* line status register          */
  55     UART_MSR = 6,  /* modem status register         */
  56     UART_SCR = 7   /* scratch register              */
  57 };
  58
  59 enum {
  60     UART_LCR_8BITS = 0x03,
  61     UART_LCR_DLAB  = 0x80
  62 };
  63
  64 enum {
  65     UART_MCR_DTR   = 0x01,
  66     UART_MCR_RTS   = 0x02,
  67     UART_MCR_OUT1  = 0x04,
  68     UART_MCR_OUT2  = 0x08,
  69     UART_MCR_LOOP  = 0x10
  70 };
  71
  72 enum {
  73     UART_LSR_DR    = 0x01,
  74     UART_LSR_OE    = 0x02,
  75     UART_LSR_PE    = 0x04,
  76     UART_LSR_FE    = 0x08,
  77     UART_LSR_THRE  = 0x20
  78 };
  79
  80 static unsigned uart_baud_rate = 115200;
  81 #define UART_PORT_ADDR  COM1_PORT_ADDR
  82
  83 #define UART_CLOCK  1843200   /* 1.8432 MHz clock */
  84
  85 #define WRITE(r, v)  outb(UART_PORT_ADDR + UART_##r, v)
  86 #define READ(r)      inb(UART_PORT_ADDR + UART_##r)
  87 #define DELAY(x)     { volatile int _d_; for (_d_ = 0; _d_ < (10000*x); _d_++) ; }
  88
  89 static int uart_initted = 0;   /* 1 if init'ed */
  90
  91 static int
  92 uart_probe( void )
  93 {
  94     /* Verify that the Scratch Register is accessible */
  95
  96     WRITE( SCR, 0x5a );
  97     if (READ(SCR) != 0x5a) return 0;
  98     WRITE( SCR, 0xa5 );
  99     if (READ(SCR) != 0xa5) return 0;
 100     return 1;
 101 }
 102
 103 static void
 104 uart_set_baud_rate( unsigned long baud_rate )
 105 {
 106     const unsigned char lcr = READ( LCR );
 107     unsigned long       div;
 108
 109     if (baud_rate == 0) baud_rate = 9600;
 110     div = UART_CLOCK / 16 / baud_rate;
 111     WRITE( LCR, lcr | UART_LCR_DLAB );
 112     WRITE( DLM, (unsigned char)(div >> 8) );
 113     WRITE( DLL, (unsigned char) div );
 114     WRITE( LCR, lcr & ~UART_LCR_DLAB);
 115 }
 116
 117 static void
 118 uart_putc( char c )
 119 {
 120     if (!uart_initted) return;
 121
 122     /* Wait for THR empty */
 123     while ( !(READ(LSR) & UART_LSR_THRE) ) DELAY(1);
 124
 125     WRITE( THR, c );
 126 }
 127
 128 static int
 129 uart_getc( void )
 130 {
 131     /*
 132      * This function returns:
 133      * -1 : no data
 134      * -2 : receiver error
 135      * >0 : character received
 136      */
 137
 138     unsigned char lsr;
 139
 140     if (!uart_initted) return -1;
 141
 142     lsr = READ( LSR );
 143
 144     if ( lsr & (UART_LSR_FE | UART_LSR_PE | UART_LSR_OE) )
 145     {
 146         READ( RBR ); /* discard */
 147         return -2;
 148     }
 149
 150     if ( lsr & UART_LSR_DR )
 151     {
 152         return READ( RBR );
 153     }
 154
 155     return -1;
 156 }
 157
 158 int serial_init( void )
 159 {
 160     unsigned serial_baud_rate = 0;
 161
 162     if ( uart_probe() == 0 ) return 0;
 163
 164     /* Disable hardware interrupts */
 165
 166     WRITE( MCR, 0 );
 167     WRITE( IER, 0 );
 168
 169     /* Disable FIFO's for 16550 devices */
 170
 171     WRITE( FCR, 0 );
 172
 173     /* Set for 8-bit, no parity, DLAB bit cleared */
 174
 175     WRITE( LCR, UART_LCR_8BITS );
 176
 177     /* Set baud rate - use the supplied boot-arg if available */
 178
 179     if (PE_parse_boot_argn("serialbaud", &serial_baud_rate, sizeof (serial_baud_rate)))
 180     {
 181             /* Valid divisor? */
 182             if (!((UART_CLOCK / 16) % serial_baud_rate)) {
 183                     uart_baud_rate = serial_baud_rate;
 184             }
 185     }
 186     uart_set_baud_rate( uart_baud_rate );
 187
 188     /* Assert DTR# and RTS# lines (OUT2?) */
 189
 190     WRITE( MCR, UART_MCR_DTR | UART_MCR_RTS );
 191
 192     /* Clear any garbage in the input buffer */
 193
 194     READ( RBR );
 195
 196     uart_initted = 1;
 197
 198     return 1;
 199 }
 200
 201 void serial_putc( char c )
 202 {
 203     uart_putc(c);
 204 }
 205
 206 int serial_getc( void )
 207 {
 208     return uart_getc();
 209 }