64 lines
1,003 B
C
64 lines
1,003 B
C
#include "types.h"
|
|
#include "param.h"
|
|
#include "memlayout.h"
|
|
#include "riscv.h"
|
|
#include "proc.h"
|
|
#include "spinlock.h"
|
|
#include "defs.h"
|
|
|
|
//
|
|
// qemu -machine virt has a 16550a UART
|
|
// qemu/hw/riscv/virt.c
|
|
// http://byterunner.com/16550.html
|
|
//
|
|
// caller should lock.
|
|
//
|
|
|
|
// address of one of the registers
|
|
#define R(reg) ((volatile unsigned char *)(UART0 + reg))
|
|
|
|
void
|
|
uartinit(void)
|
|
{
|
|
// disable interrupts -- IER
|
|
*R(1) = 0x00;
|
|
|
|
// special mode to set baud rate
|
|
*R(3) = 0x80;
|
|
|
|
// LSB for baud rate of 38.4K
|
|
*R(0) = 0x03;
|
|
|
|
// MSB for baud rate of 38.4K
|
|
*R(1) = 0x00;
|
|
|
|
// leave set-baud mode,
|
|
// and set word length to 8 bits, no parity.
|
|
*R(3) = 0x03;
|
|
|
|
// reset and enable FIFOs -- FCR.
|
|
*R(2) = 0x07;
|
|
|
|
// enable receive interrupts -- IER.
|
|
*R(1) = 0x01;
|
|
}
|
|
|
|
void
|
|
uartputc(int c)
|
|
{
|
|
*R(0) = c;
|
|
}
|
|
|
|
uint
|
|
uartgetc(void)
|
|
{
|
|
// XXX this isn't right, must check there's data in the FIFO.
|
|
return *R(0);
|
|
}
|
|
|
|
void
|
|
uartintr(void)
|
|
{
|
|
int c = uartgetc();
|
|
printf("%x ", c & 0xff);
|
|
}
|