xv6

port of xv6 to x86-64
git clone http://frotz.net/git/xv6.git
Log | Files | Refs | README | LICENSE

uart.c (1345B)

      1 // Intel 8250 serial port (UART).
      2 
      3 #include "types.h"
      4 #include "defs.h"
      5 #include "param.h"
      6 #include "traps.h"
      7 #include "spinlock.h"
      8 #include "fs.h"
      9 #include "file.h"
     10 #include "mmu.h"
     11 #include "proc.h"
     12 #include "x86.h"
     13 
     14 #define COM1    0x3f8
     15 
     16 static int uart;    // is there a uart?
     17 
     18 void
     19 uartearlyinit(void)
     20 {
     21   char *p;
     22 
     23   // Turn off the FIFO
     24   outb(COM1+2, 0);
     25   
     26   // 9600 baud, 8 data bits, 1 stop bit, parity off.
     27   outb(COM1+3, 0x80);    // Unlock divisor
     28   outb(COM1+0, 115200/9600);
     29   outb(COM1+1, 0);
     30   outb(COM1+3, 0x03);    // Lock divisor, 8 data bits.
     31   outb(COM1+4, 0);
     32   outb(COM1+1, 0x01);    // Enable receive interrupts.
     33 
     34   // If status is 0xFF, no serial port.
     35   if(inb(COM1+5) == 0xFF)
     36     return;
     37   uart = 1;
     38 
     39   // Announce that we're here.
     40   for(p="xv6...\n"; *p; p++)
     41     uartputc(*p);
     42 }
     43 
     44 void
     45 uartinit(void)
     46 {
     47   if (!uart)
     48     return;
     49 
     50   // Acknowledge pre-existing interrupt conditions;
     51   // enable interrupts.
     52   inb(COM1+2);
     53   inb(COM1+0);
     54   picenable(IRQ_COM1);
     55   ioapicenable(IRQ_COM1, 0);
     56 }
     57 
     58 void
     59 uartputc(int c)
     60 {
     61   int i;
     62 
     63   if(!uart)
     64     return;
     65   for(i = 0; i < 128 && !(inb(COM1+5) & 0x20); i++)
     66     microdelay(10);
     67   outb(COM1+0, c);
     68 }
     69 
     70 static int
     71 uartgetc(void)
     72 {
     73   if(!uart)
     74     return -1;
     75   if(!(inb(COM1+5) & 0x01))
     76     return -1;
     77   return inb(COM1+0);
     78 }
     79 
     80 void
     81 uartintr(void)
     82 {
     83   consoleintr(uartgetc);
     84 }