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 };
  57
  58 enum {
  59     UART_LCR_8BITS = 0x03,
  60     UART_LCR_DLAB  = 0x80
  61 };
  62
  63 enum {
  64     UART_MCR_DTR   = 0x01,
  65     UART_MCR_RTS   = 0x02,
  66     UART_MCR_OUT1  = 0x04,
  67     UART_MCR_OUT2  = 0x08,
  68     UART_MCR_LOOP  = 0x10
  69 };
  70
  71 enum {
  72     UART_LSR_DR    = 0x01,
  73     UART_LSR_OE    = 0x02,
  74     UART_LSR_PE    = 0x04,
  75     UART_LSR_FE    = 0x08,
  76     UART_LSR_THRE  = 0x20
  77 };
  78
  79 static unsigned uart_baud_rate = 115200;
  80 #define UART_PORT_ADDR  COM1_PORT_ADDR
  81
  82 #define UART_CLOCK  1843200   /* 1.8432 MHz clock */
  83
  84 #define WRITE(r, v)  outb(UART_PORT_ADDR + UART_##r, v)
  85 #define READ(r)      inb(UART_PORT_ADDR + UART_##r)
  86 #define DELAY(x)     { volatile int _d_; for (_d_ = 0; _d_ < (10000*x); _d_++) ; }
  87
  88 static int uart_initted = 0;   /* 1 if init'ed */
  89
  90 static int
  91 uart_probe( void )
  92 {
  93     /* Verify that the Divisor Register is accessible */
  94
  95     WRITE( LCR, UART_LCR_DLAB );
  96     WRITE( DLL, 0x5a );
  97     if (READ(DLL) != 0x5a) return 0;
  98     WRITE( DLL, 0xa5 );
  99     if (READ(DLL) != 0xa5) return 0;
 100     WRITE( LCR, 0x00 );
 101     return 1;
 102 }
 103
 104 static void
 105 uart_set_baud_rate( unsigned long baud_rate )
 106 {
 107     const unsigned char lcr = READ( LCR );
 108     unsigned long       div;
 109
 110     if (baud_rate == 0) baud_rate = 9600;
 111     div = UART_CLOCK / 16 / baud_rate;
 112     WRITE( LCR, lcr | UART_LCR_DLAB );
 113     WRITE( DLM, (unsigned char)(div >> 8) );
 114     WRITE( DLL, (unsigned char) div );
 115     WRITE( LCR, lcr & ~UART_LCR_DLAB);
 116 }
 117
 118 static void
 119 uart_putc( char c )
 120 {
 121     if (!uart_initted) return;
 122
 123     /* Wait for THR empty */
 124     while ( !(READ(LSR) & UART_LSR_THRE) ) DELAY(1);
 125
 126     WRITE( THR, c );
 127 }
 128
 129 static int
 130 uart_getc( void )
 131 {
 132     /*
 133      * This function returns:
 134      * -1 : no data
 135      * -2 : receiver error
 136      * >0 : character received
 137      */
 138
 139     unsigned char lsr;
 140
 141     if (!uart_initted) return -1;
 142
 143     lsr = READ( LSR );
 144
 145     if ( lsr & (UART_LSR_FE | UART_LSR_PE | UART_LSR_OE) )
 146     {
 147         READ( RBR ); /* discard */
 148         return -2;
 149     }
 150
 151     if ( lsr & UART_LSR_DR )
 152     {
 153         return READ( RBR );
 154     }
 155
 156     return -1;
 157 }
 158
 159 int serial_init( void )
 160 {
 161     unsigned serial_baud_rate = 0;
 162
 163     if ( /*uart_initted ||*/ uart_probe() == 0 ) return 0;
 164
 165     /* Disable hardware interrupts */
 166
 167     WRITE( MCR, 0 );
 168     WRITE( IER, 0 );
 169
 170     /* Disable FIFO's for 16550 devices */
 171
 172     WRITE( FCR, 0 );
 173
 174     /* Set for 8-bit, no parity, DLAB bit cleared */
 175
 176     WRITE( LCR, UART_LCR_8BITS );
 177
 178     /* Set baud rate - use the supplied boot-arg if available */
 179
 180     if (PE_parse_boot_arg("serialbaud", &serial_baud_rate))
 181     {
 182             /* Valid divisor? */
 183             if (!((UART_CLOCK / 16) % serial_baud_rate)) {
 184                     uart_baud_rate = serial_baud_rate;
 185             }
 186     }
 187     uart_set_baud_rate( uart_baud_rate );
 188
 189     /* Assert DTR# and RTS# lines (OUT2?) */
 190
 191     WRITE( MCR, UART_MCR_DTR | UART_MCR_RTS );
 192
 193     /* Clear any garbage in the input buffer */
 194
 195     READ( RBR );
 196
 197     uart_initted = 1;
 198
 199     return 1;
 200 }
 201
 202 void serial_putc( char c )
 203 {
 204     uart_putc(c);
 205     if (c == '\n') uart_putc('\r');
 206 }
 207
 208 int serial_getc( void )
 209 {
 210     return uart_getc();
 211 }