com32/gdbstub/serial.c

   1 /*
   2  * The serial port interface routines implement a simple polled i/o
   3  * interface to a standard serial port.  Due to the space restrictions
   4  * for the boot blocks, no BIOS support is used (since BIOS requires
   5  * expensive real/protected mode switches), instead the rudimentary
   6  * BIOS support is duplicated here.
   7  *
   8  * The base address and speed for the i/o port are passed from the
   9  * Makefile in the COMCONSOLE and CONSPEED preprocessor macros.  The
  10  * line control parameters are currently hard-coded to 8 bits, no
  11  * parity, 1 stop bit (8N1).  This can be changed in init_serial().
  12  */
  13
  14 #include <stddef.h>
  15 #include <sys/io.h>
  16 #include "serial.h"
  17
  18 /* Set default values if none specified */
  19
  20 #ifndef COMCONSOLE
  21 #define COMCONSOLE      0x3f8
  22 #endif
  23
  24 #ifndef COMSPEED
  25 #define COMSPEED        9600
  26 #endif
  27
  28 #ifndef COMDATA
  29 #define COMDATA         8
  30 #endif
  31
  32 #ifndef COMPARITY
  33 #define COMPARITY       0
  34 #endif
  35
  36 #ifndef COMSTOP
  37 #define COMSTOP         1
  38 #endif
  39
  40 #undef UART_BASE
  41 #define UART_BASE ( COMCONSOLE )
  42
  43 #undef UART_BAUD
  44 #define UART_BAUD ( COMSPEED )
  45
  46 #if ((115200%UART_BAUD) != 0)
  47 #error Bad ttys0 baud rate
  48 #endif
  49
  50 #define COMBRD (115200/UART_BAUD)
  51
  52 /* Line Control Settings */
  53 #define UART_LCS ( ( ( (COMDATA) - 5 )  << 0 ) | \
  54                    ( ( (COMPARITY) )    << 3 ) | \
  55                    ( ( (COMSTOP) - 1 )  << 2 ) )
  56
  57 /* Data */
  58 #define UART_RBR 0x00
  59 #define UART_TBR 0x00
  60
  61 /* Control */
  62 #define UART_IER 0x01
  63 #define UART_IIR 0x02
  64 #define UART_FCR 0x02
  65 #define UART_LCR 0x03
  66 #define UART_MCR 0x04
  67 #define UART_DLL 0x00
  68 #define UART_DLM 0x01
  69
  70 /* Status */
  71 #define UART_LSR 0x05
  72 #define  UART_LSR_TEMPT 0x40    /* Transmitter empty */
  73 #define  UART_LSR_THRE  0x20    /* Transmit-hold-register empty */
  74 #define  UART_LSR_BI    0x10    /* Break interrupt indicator */
  75 #define  UART_LSR_FE    0x08    /* Frame error indicator */
  76 #define  UART_LSR_PE    0x04    /* Parity error indicator */
  77 #define  UART_LSR_OE    0x02    /* Overrun error indicator */
  78 #define  UART_LSR_DR    0x01    /* Receiver data ready */
  79
  80 #define UART_MSR 0x06
  81 #define UART_SCR 0x07
  82
  83 #define uart_readb(addr) inb(addr)
  84 #define uart_writeb(val,addr) outb((val),(addr))
  85
  86 /*
  87  * void serial_putc(int ch);
  88  *      Write character `ch' to port UART_BASE.
  89  */
  90 void serial_putc(int ch)
  91 {
  92     int status;
  93     for (;;) {
  94         status = uart_readb(UART_BASE + UART_LSR);
  95         if (status & UART_LSR_THRE) {
  96             /* TX buffer emtpy */
  97             uart_writeb(ch, UART_BASE + UART_TBR);
  98             break;
  99         }
 100     }
 101 }
 102
 103 /*
 104  * int serial_getc(void);
 105  *      Read a character from port UART_BASE.
 106  */
 107 int serial_getc(void)
 108 {
 109     int status;
 110     int ch;
 111     do {
 112         status = uart_readb(UART_BASE + UART_LSR);
 113     } while ((status & 1) == 0);
 114     ch = uart_readb(UART_BASE + UART_RBR);      /* fetch (first) character */
 115     ch &= 0x7f;                 /* remove any parity bits we get */
 116     if (ch == 0x7f) {           /* Make DEL... look like BS */
 117         ch = 0x08;
 118     }
 119     return ch;
 120 }
 121
 122 /*
 123  * int serial_init(void);
 124  *      Initialize port UART_BASE to speed COMSPEED, line settings 8N1.
 125  */
 126 void serial_init(void)
 127 {
 128     int status;
 129     int divisor, lcs;
 130
 131     divisor = COMBRD;
 132     lcs = UART_LCS;
 133
 134 #ifdef COMPRESERVE
 135     lcs = uart_readb(UART_BASE + UART_LCR) & 0x7f;
 136     uart_writeb(0x80 | lcs, UART_BASE + UART_LCR);
 137     divisor =
 138         (uart_readb(UART_BASE + UART_DLM) << 8) | uart_readb(UART_BASE +
 139                                                              UART_DLL);
 140     uart_writeb(lcs, UART_BASE + UART_LCR);
 141 #endif
 142
 143     /* Set Baud Rate Divisor to COMSPEED, and test to see if the
 144      * serial port appears to be present.
 145      */
 146     uart_writeb(0x80 | lcs, UART_BASE + UART_LCR);
 147     uart_writeb(0xaa, UART_BASE + UART_DLL);
 148     if (uart_readb(UART_BASE + UART_DLL) != 0xaa) {
 149         goto out;
 150     }
 151     uart_writeb(0x55, UART_BASE + UART_DLL);
 152     if (uart_readb(UART_BASE + UART_DLL) != 0x55) {
 153         goto out;
 154     }
 155     uart_writeb(divisor & 0xff, UART_BASE + UART_DLL);
 156     if (uart_readb(UART_BASE + UART_DLL) != (divisor & 0xff)) {
 157         goto out;
 158     }
 159     uart_writeb(0xaa, UART_BASE + UART_DLM);
 160     if (uart_readb(UART_BASE + UART_DLM) != 0xaa) {
 161         goto out;
 162     }
 163     uart_writeb(0x55, UART_BASE + UART_DLM);
 164     if (uart_readb(UART_BASE + UART_DLM) != 0x55) {
 165         goto out;
 166     }
 167     uart_writeb((divisor >> 8) & 0xff, UART_BASE + UART_DLM);
 168     if (uart_readb(UART_BASE + UART_DLM) != ((divisor >> 8) & 0xff)) {
 169         goto out;
 170     }
 171     uart_writeb(lcs, UART_BASE + UART_LCR);
 172
 173     /* disable interrupts */
 174     uart_writeb(0x0, UART_BASE + UART_IER);
 175
 176     /* disable fifo's */
 177     uart_writeb(0x00, UART_BASE + UART_FCR);
 178
 179     /* Set clear to send, so flow control works... */
 180     uart_writeb((1 << 1), UART_BASE + UART_MCR);
 181
 182     /* Flush the input buffer. */
 183     do {
 184         /* rx buffer reg
 185          * throw away (unconditionally the first time)
 186          */
 187         (void)uart_readb(UART_BASE + UART_RBR);
 188         /* line status reg */
 189         status = uart_readb(UART_BASE + UART_LSR);
 190     } while (status & UART_LSR_DR);
 191 out:
 192     return;
 193 }