basekernel/kernel/serial.c

/*
Copyright (C) 2016-2019 The University of Notre Dame
This software is distributed under the GNU General Public License.
See the file LICENSE for details.
*/

/* Derived from: https://wiki.osdev.org/Serial_Ports#Example_Code
  For more info:
     https://wiki.osdev.org/Serial_Ports
     http://www.webcitation.org/5ugQv5JOw
  TODO: Interrupt support; polling IO is not a good idea for carbon free air
*/

#include "kernel/types.h"
#include "ioports.h"
#include "interrupt.h"
#include "string.h"
#include "device.h"

#define COM1 0x3f8
#define COM2 0x2F8
#define COM3 0x3E8
#define COM4 0x2E8

#define SERIAL_DATA 0		// If DLAB disabled in LCR

#define SERIAL_IRQ_ENABLE 1	// If DLAB disabled in LCR
#define SERIAL_IRQ_DATA_AVAILABILE (0x01 << 0)
#define SERIAL_IRQ_TRASMITTER_EMPTY (0x01 << 1)
#define SERIAL_IRQ_ERROR (0x01 << 2)
#define SERIAL_IRQ_STATUS_CHANGE (0x01 << 3)

#define SERIAL_DIVISOR_LO 0	// If DLAB enabled in LCR

#define SERIAL_DIVISOR_HI 1	// If DLAB enabled in LCR

#define SERIAL_FCR 2
#define SERIAL_FIFO_ENABLE (0x01 << 0)
#define SERIAL_FIFO_CLEAR_RECEIVER (0x01 << 1)
#define SERIAL_FIFO_CLEAR_TRANSMITTER (0x01 << 2)
#define SERIAL_FIFO_DMA_MODE (0x01 << 3)
#define SERIAL_TRIGGER_LEVEL0 (0x00 << 6)  // 1 byte in FIFO
#define SERIAL_TRIGGER_LEVEL1 (0x01 << 6)  // 4 bytes
#define SERIAL_TRIGGER_LEVEL2 (0x10 << 6)  // 8 bytes
#define SERIAL_TRIGGER_LEVEL3 (0x11 << 6)  // 14 bytes

#define SERIAL_LCR 3
#define SERIAL_CHARLEN_START (0x01 << 0)
#define SERIAL_STOP_BITS (0x01 << 2)
#define SERIAL_DLAB_ENABLE (0x01 << 3)

#define SERIAL_MCR 4
#define SERIAL_DATA_TERMINAL_READY (0x01 << 0)
#define SERIAL_REQUEST_TO_SEND (0x01 << 1)
#define SERIAL_AUX_OUT1 (0x01 << 2)
#define SERIAL_AUX_OUT2 (0x01 << 3)

#define SERIAL_LSR 5
#define SERIAL_DATA_AVAILABLE (0x01 << 0)
#define SERIAL_TRANSMIT_EMPTY (0x01 << 5)

#define SERIAL_MSR 6

#define SERIAL_SCRATCH 7

// units 0,1,2,3
static const int serial_ports[4] = { COM1, COM2, COM3, COM4 };
static const int serial_ports_irq[4] = { 4, 3, 4, 3 };

static void serial_interrupt(int i, int intr_code)
{
  printf("serial_interrupt %d %d\n",i,intr_code);
}



static void serial_init_port(int unit)
{
  int port = serial_ports[unit];
	//Disable interrupts
	outb(0x00, port + SERIAL_IRQ_ENABLE);
	//Enable DLAB(set baud rate divisor)
	outb(SERIAL_DLAB_ENABLE, port + SERIAL_LCR);
	//Set divisor to 3(lo byte) 38400 baud
	outb(0x03, port + SERIAL_DIVISOR_LO);
	//(hi byte)
	outb(0x00, port + SERIAL_DIVISOR_HI);
	//8 bits, no parity, one stop bit
	outb(SERIAL_CHARLEN_START * 3, port + SERIAL_LCR);
	//Enable FIFO, clear them, with 14 - byte threshold
	outb(SERIAL_FIFO_ENABLE | SERIAL_FIFO_CLEAR_RECEIVER | SERIAL_FIFO_CLEAR_TRANSMITTER | SERIAL_TRIGGER_LEVEL0 , port + SERIAL_FCR);
	//IRQs enabled, RTS / DSR set
	outb(SERIAL_DATA_TERMINAL_READY | SERIAL_REQUEST_TO_SEND | SERIAL_AUX_OUT2, port + SERIAL_MCR);

	// setup interrupt support
  interrupt_register(serial_ports_irq[unit], serial_interrupt);
  interrupt_enable(serial_ports_irq[unit]);
  // + received data available
	outb(0x01, port + SERIAL_IRQ_ENABLE); 
  
	printf("[COM%d] serial_init_port %x: ready.\n",unit,port);
}


static int serial_received(int port)
{
	return inb(port + SERIAL_LSR) & SERIAL_DATA_AVAILABLE;
}

static int is_transmit_empty(int port)
{
	return inb(port + SERIAL_LSR) & SERIAL_TRANSMIT_EMPTY;
}

static int is_valid_port(uint8_t port_no)
{
	return port_no < sizeof(serial_ports) / sizeof(int);
}

int serial_read(uint8_t port_no)
{
	if(!is_valid_port(port_no))
		return -1;

	while(serial_received(serial_ports[port_no]) == 0);
	printf("[COM%d]\n",port_no);
	return inb(serial_ports[port_no]);
}

int serial_read_nonblock(uint8_t port_no)
{
	if(!is_valid_port(port_no))
		return -1;

	if (serial_received(serial_ports[port_no]) == 0) return -1;
	printf("[COM%d]\n",port_no);
	return inb(serial_ports[port_no]);
}

int serial_write(uint8_t port_no, char a)
{
	if(!is_valid_port(port_no))
		return -1;

	while(is_transmit_empty(serial_ports[port_no]) == 0);
	outb(a, serial_ports[port_no]);
	return 0;
}

int serial_device_probe( int unit, int *blocksize, int *nblocks, char *info )
{
	if(unit<0 || unit>3) return 0;
	// TODO probing for real hardware
	// reinit, second time (first time in serial_init, but needed to register the device)
	serial_init_port(unit);
	*blocksize = 1;
	*nblocks = 0;
	strcpy(info,"serial");
	return 1;
}

int serial_device_read( int unit, void *data, int length, int offset )
{
	int i,byte;
	char *cdata = data;
	for(i=0;i<length;i++) {
		byte = serial_read(unit);
		if (byte==-1) break;
		cdata[i] = (char)byte; 
	}
	return length;
}

int serial_device_read_nonblock( int unit, void *data, int length, int offset )
{
	int i,byte;
	char *cdata = data;
	for(i=0;i<length;i++) {
		byte = serial_read_nonblock(unit);
		if (byte==-1) break;
		cdata[i] = (char)byte;
	}
	return length;
}

int serial_device_write( int unit, const void *data, int length, int offset )
{
	int i;
	const char *cdata = data;
	for(i=0;i<length;i++) {
		serial_write(unit,cdata[i]);
	}
	return length;
}


static struct device_driver serial_driver = {
       .name           = "serial",
       .probe          = serial_device_probe,
       .read           = serial_device_read,
       .read_nonblock  = serial_device_read_nonblock,
       .write          = serial_device_write
};

void serial_init()
{
	int i;
	for(i = 0; i < sizeof(serial_ports) / sizeof(int); i++) {
		serial_init_port(i);
	}
	device_driver_register(&serial_driver);
}