pexpert/i386/pe_serial.c

   1 /*
   2  * Copyright (c) 2000 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 void    serial_putc(char);
  38 int     serial_getc(void);
  39 int     serial_init(void);
  40
  41 /* standard port addresses */
  42 enum {
  43     COM1_PORT_ADDR = 0x3f8,
  44     COM2_PORT_ADDR = 0x2f8
  45 };
  46
  47 /* UART register offsets */
  48 enum {
  49     UART_RBR = 0,  /* receive buffer Register   (R) */
  50     UART_THR = 0,  /* transmit holding register (W) */
  51     UART_DLL = 0,  /* DLAB = 1, divisor latch (LSB) */
  52     UART_IER = 1,  /* interrupt enable register     */
  53     UART_DLM = 1,  /* DLAB = 1, divisor latch (MSB) */
  54     UART_IIR = 2,  /* interrupt ident register (R)  */
  55     UART_FCR = 2,  /* fifo control register (W)     */
  56     UART_LCR = 3,  /* line control register         */
  57     UART_MCR = 4,  /* modem control register        */
  58     UART_LSR = 5,  /* line status register          */
  59     UART_MSR = 6   /* modem status register         */
  60 };
  61
  62 enum {
  63     UART_LCR_8BITS = 0x03,
  64     UART_LCR_DLAB  = 0x80
  65 };
  66
  67 enum {
  68     UART_MCR_DTR   = 0x01,
  69     UART_MCR_RTS   = 0x02,
  70     UART_MCR_OUT1  = 0x04,
  71     UART_MCR_OUT2  = 0x08,
  72     UART_MCR_LOOP  = 0x10
  73 };
  74
  75 enum {
  76     UART_LSR_DR    = 0x01,
  77     UART_LSR_OE    = 0x02,
  78     UART_LSR_PE    = 0x04,
  79     UART_LSR_FE    = 0x08,
  80     UART_LSR_THRE  = 0x20
  81 };
  82
  83 static unsigned uart_baud_rate = 115200;
  84 #define UART_PORT_ADDR  COM1_PORT_ADDR
  85
  86 #define UART_CLOCK  1843200   /* 1.8432 MHz clock */
  87
  88 #define WRITE(r, v)  outb(UART_PORT_ADDR + UART_##r, v)
  89 #define READ(r)      inb(UART_PORT_ADDR + UART_##r)
  90 #define DELAY(x)     { volatile int _d_; for (_d_ = 0; _d_ < (10000*x); _d_++) ; }
  91
  92 static int uart_initted = 0;   /* 1 if init'ed */
  93
  94 static int
  95 uart_probe( void )
  96 {
  97     /* Verify that the Divisor Register is accessible */
  98
  99     WRITE( LCR, UART_LCR_DLAB );
 100     WRITE( DLL, 0x5a );
 101     if (READ(DLL) != 0x5a) return 0;
 102     WRITE( DLL, 0xa5 );
 103     if (READ(DLL) != 0xa5) return 0;
 104     WRITE( LCR, 0x00 );
 105     return 1;
 106 }
 107
 108 static void
 109 uart_set_baud_rate( unsigned long baud_rate )
 110 {
 111     const unsigned char lcr = READ( LCR );
 112     unsigned long       div;
 113
 114     if (baud_rate == 0) baud_rate = 9600;
 115     div = UART_CLOCK / 16 / baud_rate;
 116     WRITE( LCR, lcr | UART_LCR_DLAB );
 117     WRITE( DLM, (unsigned char)(div >> 8) );
 118     WRITE( DLL, (unsigned char) div );
 119     WRITE( LCR, lcr & ~UART_LCR_DLAB);
 120 }
 121
 122 static void
 123 uart_putc( char c )
 124 {
 125     if (!uart_initted) return;
 126
 127     /* Wait for THR empty */
 128     while ( !(READ(LSR) & UART_LSR_THRE) ) DELAY(1);
 129
 130     WRITE( THR, c );
 131 }
 132
 133 static int
 134 uart_getc( void )
 135 {
 136     /*
 137      * This function returns:
 138      * -1 : no data
 139      * -2 : receiver error
 140      * >0 : character received
 141      */
 142
 143     unsigned char lsr;
 144
 145     if (!uart_initted) return -1;
 146
 147     lsr = READ( LSR );
 148
 149     if ( lsr & (UART_LSR_FE | UART_LSR_PE | UART_LSR_OE) )
 150     {
 151         READ( RBR ); /* discard */
 152         return -2;
 153     }
 154
 155     if ( lsr & UART_LSR_DR )
 156     {
 157         return READ( RBR );
 158     }
 159
 160     return -1;
 161 }
 162
 163 int serial_init( void )
 164 {
 165     unsigned serial_baud_rate = 0;
 166
 167     if ( /*uart_initted ||*/ uart_probe() == 0 ) return 0;
 168
 169     /* Disable hardware interrupts */
 170
 171     WRITE( MCR, 0 );
 172     WRITE( IER, 0 );
 173
 174     /* Disable FIFO's for 16550 devices */
 175
 176     WRITE( FCR, 0 );
 177
 178     /* Set for 8-bit, no parity, DLAB bit cleared */
 179
 180     WRITE( LCR, UART_LCR_8BITS );
 181
 182     /* Set baud rate - use the supplied boot-arg if available */
 183
 184     if (PE_parse_boot_arg("serialbaud", &serial_baud_rate))
 185     {
 186             /* Valid divisor? */
 187             if (!((UART_CLOCK / 16) % serial_baud_rate)) {
 188                     uart_baud_rate = serial_baud_rate;
 189             }
 190     }
 191     uart_set_baud_rate( uart_baud_rate );
 192
 193     /* Assert DTR# and RTS# lines (OUT2?) */
 194
 195     WRITE( MCR, UART_MCR_DTR | UART_MCR_RTS );
 196
 197     /* Clear any garbage in the input buffer */
 198
 199     READ( RBR );
 200
 201     uart_initted = 1;
 202
 203     return 1;
 204 }
 205
 206 void serial_putc( char c )
 207 {
 208     uart_putc(c);
 209     if (c == '\n') uart_putc('\r');
 210 }
 211
 212 int serial_getc( void )
 213 {
 214     return uart_getc();
 215 }