76 lines
1.2 KiB
C
76 lines
1.2 KiB
C
// Intel 8250 serial port (UART).
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#include "types.h"
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#include "defs.h"
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#include "param.h"
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#include "traps.h"
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#include "spinlock.h"
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#include "dev.h"
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#include "mmu.h"
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#include "proc.h"
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#include "x86.h"
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#define COM1 0x3f8
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static int uart; // is there a uart?
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void
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uartinit(void)
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{
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char *p;
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// Turn off the FIFO
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outb(COM1+2, 0);
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// 9600 baud, 8 data bits, 1 stop bit, parity off.
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outb(COM1+3, 0x80); // Unlock divisor
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outb(COM1+0, 115200/9600);
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outb(COM1+1, 0);
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outb(COM1+3, 0x03); // Lock divisor, 8 data bits.
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outb(COM1+4, 0);
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outb(COM1+1, 0x01); // Enable receive interrupts.
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// If status is 0xFF, no serial port.
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if(inb(COM1+5) == 0xFF)
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return;
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uart = 1;
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// Acknowledge pre-existing interrupt conditions;
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// enable interrupts.
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inb(COM1+2);
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inb(COM1+0);
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picenable(IRQ_COM1);
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ioapicenable(IRQ_COM1, 0);
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// Announce that we're here.
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for(p="xv6...\n"; *p; p++)
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uartputc(*p);
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}
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void
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uartputc(int c)
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{
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int i;
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if(!uart)
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return;
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for(i = 0; i < 128 && !(inb(COM1+5) & 0x20); i++)
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microdelay(10);
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outb(COM1+0, c);
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}
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static int
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uartgetc(void)
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{
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if(!uart)
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return -1;
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if(!(inb(COM1+5) & 0x01))
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return -1;
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return inb(COM1+0);
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}
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void
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uartintr(void)
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{
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consoleintr(uartgetc);
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}
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