kernel/serial.c

   1 /*
   2  *    Copyright (c) 2008 Joshua Phillips. All rights reserved.
   3  *
   4  *  Redistribution and use in source and binary forms, with or without
   5  *  modification, are permitted provided that the following conditions are
   6  *  met:
   7  *
   8  *    1. Redistributions of source code must retain the above copyright
   9  *       notice, this list of conditions and the following disclaimer.
  10  *    2. Redistributions in binary form must reproduce the above copyright
  11  *       notice, this list of conditions and the following disclaimer in
  12  *       the documentation and/or other materials provided with the
  13  *       distribution.
  14  *
  15  *  THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESS OR IMPLIED
  16  *  WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  17  *  OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  18  *  DISCLAIMED. IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY
  19  *  DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  20  *  DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
  21  *  GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  22  *  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
  23  *  IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
  24  *  OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
  25  *  IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  26  */
  27
  28 #include "serial.h"
  29 #include "portio.h"
  30
  31 struct serial com1, com2, com3, com4;
  32
  33 #define com1Irq 4
  34 #define com2Irq 3
  35 #define com1Base 0x3F8
  36 #define com2Base 0x2F8
  37 #define com3Base 0x3E8
  38 #define com4Base 0x2E8
  39
  40 static int detect_uart(struct serial *self);
  41 static char sanitise_output(struct serial *self, char ch);
  42 static void send_char(struct serial *self, char ch);
  43
  44 // Probe to see if the device is there
  45 // 0 - no UART
  46 // 1 - 8250
  47 // 2 - 16450 or 8250 with scratch reg
  48 // 3 - 16550
  49 // 4 - 16550A
  50 static int detect_uart(struct serial *self)
  51 {
  52     unsigned int x, tmp;
  53
  54     // Check if UART is present
  55     tmp = inb(self->port + 4);
  56     outb(self->port + 4, 0x10);
  57     if ((inb(self->port + 6) & 0xF0))
  58         return 0;
  59     outb(self->port + 4, 0x1F);
  60     if ((inb(self->port + 6) & 0xF0) != 0xF0)
  61         return 0;
  62     outb(self->port + 4, tmp);
  63
  64     // Look for scratch register
  65     tmp = inb(self->port + 7);
  66     outb(self->port + 7, 0x55);
  67     if (inb(self->port + 7) != 0x55)
  68         return 1;
  69     outb(self->port + 7, 0xAA);
  70     if (inb(self->port + 7) != 0xAA)
  71         return 1;
  72     outb(self->port + 7, tmp);
  73
  74     // Look for a FIFO
  75     outb(self->port + 2, 1);
  76     x = inb(self->port + 2);
  77     outb(self->port + 2, 0x00);
  78     if ((x & 0x80) == 0)
  79         return 2;
  80     if ((x & 0x40) == 0)
  81         return 3;
  82     return 4;
  83 }
  84
  85 static char sanitise_output(struct serial *self, char ch)
  86 {
  87     if (ch == '\n'){
  88         // We have to send the age-old CRLF combo
  89         // for a newline
  90         send_char(self, '\r');
  91         return '\n';
  92     } else if (ch == '\b'){
  93         return 0;
  94     } else {
  95         return ch;
  96     }
  97 }
  98
  99 // send a single character
 100 static void send_char(struct serial *self, char ch)
 101 {
 102     // remove characters we don't want (control characters, etc.)
 103     if (!(ch = sanitise_output(self, ch)))
 104         return;
 105     // wait for UART to be ready
 106     while (!(inb(self->port + 5) & 0x20)){
 107         // do nothing
 108     }
 109     // send!
 110     outb(self->port, ch);
 111 }
 112
 113 bool serial_init(struct serial *self, int com_number, unsigned long baud)
 114 {
 115     unsigned int divisor;
 116
 117     switch (com_number){
 118         case 1:
 119             self->port = com1Base;
 120             self->irq = com1Irq;
 121             break;
 122         case 2:
 123             self->port = com2Base;
 124             self->irq = com2Irq;
 125             break;
 126         case 3:
 127             self->port = com3Base;
 128             self->irq = com1Irq;
 129             break;
 130         case 4:
 131             self->port = com4Base;
 132             self->irq = com2Irq;
 133             break;
 134         default:
 135             return false;
 136     }
 137
 138     if (detect_uart(self) == 0){
 139         // couldn't actually find the device
 140         return false;
 141     }
 142
 143     divisor = 115200 / baud;
 144     outb(self->port + 1, 0x00); // disable all interrupts
 145     outb(self->port + 3, 0x80); // enable 'DLAB' - baud rate divisor
 146     outb(self->port + 0, divisor); // divisor (lower)
 147     outb(self->port + 1, divisor >> 8); // divisor (upper)
 148     outb(self->port + 3, 0x03); // 8-bits, no parity, one stop bit
 149     outb(self->port + 2, 0xC7); // enable FIFO, clear them, with 14-byte threshold
 150     outb(self->port + 4, 0x0B); // enable (something)
 151     outb(self->port + 4, inb(self->port + 4) | 8); // set OUT2 bit to enable interrupts
 152     outb(self->port + 1, 0x01); // enable ERBFI (receiver buffer full) interrupt
 153
 154     self->initialized = true;
 155     return true;
 156 }
 157
 158 bool serial_is_initialized(struct serial *self)
 159 {
 160     return self->initialized;
 161 }
 162
 163 void serial_send(struct serial *self, const char *str)
 164 {
 165     while (*str){
 166         send_char(self, *str);
 167         str++;
 168     }
 169 }