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#include "uart.h"
#include "csr.h"
#include "plic.h"
#include <stdint.h>
// the UART control registers are memory-mapped
// at address UART0. this macro returns the
// address of one of the registers.
#define Reg(reg) ((volatile unsigned char *)(UART0 + (reg)))
// the UART control registers.
// some have different meanings for
// read vs write.
// see http://byterunner.com/16550.html
#define RHR 0 // receive holding register (for input bytes)
#define THR 0 // transmit holding register (for output bytes)
#define IER 1 // interrupt enable register
#define IER_RX_ENABLE (1<<0)
#define IER_TX_ENABLE (1<<1)
#define FCR 2 // FIFO control register
#define FCR_FIFO_ENABLE (1<<0)
#define FCR_FIFO_CLEAR (3<<1) // clear the content of the two FIFOs
#define ISR 2 // interrupt status register
#define LCR 3 // line control register
#define LCR_EIGHT_BITS (3<<0)
#define LCR_BAUD_LATCH (1<<7) // special mode to set baud rate
#define LSR 5 // line status register
#define LSR_RX_READY (1<<0) // input is waiting to be read from RHR
#define LSR_TX_IDLE (1<<5) // THR can accept another character to send
#define ReadReg(reg) (*(Reg(reg)))
#define WriteReg(reg, v) (*(Reg(reg)) = (v))
int uart_init(void)
{
// disable interrupts.
WriteReg(IER, 0x00);
// special mode to set baud rate.
WriteReg(LCR, LCR_BAUD_LATCH);
// LSB for baud rate of 38.4K.
WriteReg(0, 0x03);
// MSB for baud rate of 38.4K.
WriteReg(1, 0x00);
// leave set-baud mode,
// and set word length to 8 bits, no parity.
WriteReg(LCR, LCR_EIGHT_BITS);
// reset and enable FIFOs.
WriteReg(FCR, FCR_FIFO_ENABLE | FCR_FIFO_CLEAR);
// enable transmit and receive interrupts.
// WriteReg(IER, IER_TX_ENABLE | IER_RX_ENABLE);
//enable UART0 in PLIC
plic_irq_enable(UART0_IRQ);
//set UART0 priority in PLIC
plic_prio_set(UART0_IRQ, 1);
//register callback for UART0
//plic_register_callback(UART0_IRQ, uart_intr);
puts("[UART0] : Uart Init Done, this is Test output!");
return 0;
}
static inline void uart_putc_nolock(int ch)
{
// wait for Transmit Holding Empty to be set in LSR.
while((ReadReg(LSR) & LSR_TX_IDLE) == 0)
;
WriteReg(THR, ch);
return;
}
int uart_putc(int ch)
{
int intr_enable = riscv_mintr_get();
riscv_mintr_off();
uart_putc_nolock(ch);
riscv_mintr_restore(intr_enable);
return 1;
}
int uart_puts(const char* str)
{
int i;
int intr_enable = riscv_mintr_get();
riscv_mintr_off();
for(i=0;str[i]!=0;i++)
{
uart_putc_nolock(str[i]);
}
uart_putc_nolock('\n');
riscv_mintr_restore(intr_enable);
return i;
}
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