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sortix--sortix/kernel/uart.cpp
2014-11-18 18:10:22 +01:00

175 lines
4.7 KiB
C++

/*******************************************************************************
Copyright(C) Jonas 'Sortie' Termansen 2011.
This file is part of Sortix.
Sortix is free software: you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free Software
Foundation, either version 3 of the License, or (at your option) any later
version.
Sortix is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
details.
You should have received a copy of the GNU General Public License along with
Sortix. If not, see <http://www.gnu.org/licenses/>.
uart.cpp
A simple serial terminal driver.
*******************************************************************************/
#include <stddef.h>
#include <stdint.h>
#include <string.h>
#include <sortix/kernel/cpu.h>
#include <sortix/kernel/ioport.h>
#include <sortix/kernel/kernel.h>
#include "vga.h"
#include "uart.h"
namespace Sortix {
namespace UART {
const unsigned TXR = 0; // Transmit register
const unsigned RXR = 0; // Receive register
const unsigned IER = 1; // Interrupt Enable
const unsigned IIR = 2; // Interrupt ID
const unsigned FCR = 2; // FIFO control
const unsigned LCR = 3; // Line control
const unsigned MCR = 4; // Modem control
const unsigned LSR = 5; // Line Status
const unsigned MSR = 6; // Modem Status
const unsigned DLL = 0; // divisor Latch Low
const unsigned DLM = 1; // divisor latch High
const unsigned LCR_DLAB = 0x80; // divisor latch access bit
const unsigned LCR_SBC = 0x40; // Set break control
const unsigned LCR_SPAR = 0x20; // Stick parity (?)
const unsigned LCR_EPAR = 0x10; // Even parity select
const unsigned LCR_PARITY = 0x08; // Parity Enable
const unsigned LCR_STOP = 0x04; // Stop bits: 0=1 bit, 1=2 bits
const unsigned LCR_WLEN5 = 0x00; // Wordlength: 5 bits
const unsigned LCR_WLEN6 = 0x01; // Wordlength: 6 bits
const unsigned LCR_WLEN7 = 0x02; // Wordlength: 7 bits
const unsigned LCR_WLEN8 = 0x03; // Wordlength: 8 bits
const unsigned LSR_TEMT = 0x40; // Transmitter empty
const unsigned LSR_THRE = 0x20; // Transmit-hold-register empty
const unsigned LSR_READY = 0x1;
const unsigned BASE_BAUD = 1843200 / 16;
const unsigned BOTH_EMPTY = LSR_TEMT | LSR_THRE;
unsigned ProbeBaud(unsigned port)
{
uint8_t lcr = inport8(port + LCR);
outport8(port + LCR, lcr | LCR_DLAB);
uint8_t dll = inport8(port + DLL);
uint8_t dlm = inport8(port + DLM);
outport8(port + LCR, lcr);
unsigned quot = dlm << 8 | dll;
return BASE_BAUD / quot;
}
void WaitForEmptyBuffers(unsigned port)
{
while ( (inport8(port + LSR) & BOTH_EMPTY) != BOTH_EMPTY );
}
const unsigned PORT = 0x3F8;
void Init()
{
unsigned baud = ProbeBaud(PORT);
outport8(PORT + LCR, 0x3); // 8n1
outport8(PORT + IER, 0); // No interrupt
outport8(PORT + FCR, 0); // No FIFO
outport8(PORT + MCR, 0x3); // DTR + RTS
unsigned divisor = 115200 / baud;
uint8_t c = inport8(PORT + LCR);
outport8(PORT + LCR, c | LCR_DLAB);
outport8(PORT + DLL, divisor >> 0 & 0xFF);
outport8(PORT + DLM, divisor >> 8 & 0xFF);
outport8(PORT + LCR, c & ~LCR_DLAB);
}
void Read(uint8_t* buffer, size_t size)
{
// Save the IER and disable interrupts.
unsigned ier = inport8(PORT + IER);
outport8(PORT + IER, 0);
for ( size_t i = 0; i < size; i++ )
{
while ( !(inport8(PORT + LSR) & LSR_READY) );
buffer[i] = inport8(PORT);
}
// Wait for transmitter to become empty and restore the IER.
WaitForEmptyBuffers(PORT);
outport8(PORT + IER, ier);
}
void Write(const void* b, size_t size)
{
const uint8_t* buffer = (const uint8_t*) b;
// Save the IER and disable interrupts.
unsigned ier = inport8(PORT + IER);
outport8(PORT + IER, 0);
for ( size_t i = 0; i < size; i++ )
{
WaitForEmptyBuffers(PORT);
outport8(PORT, buffer[i]);
}
// Wait for transmitter to become empty and restore the IER.
WaitForEmptyBuffers(PORT);
outport8(PORT + IER, ier);
}
void WriteChar(char c)
{
// Save the IER and disable interrupts.
unsigned ier = inport8(PORT + IER);
outport8(PORT + IER, 0);
WaitForEmptyBuffers(PORT);
outport8(PORT, c);
// Wait for transmitter to become empty and restore the IER.
WaitForEmptyBuffers(PORT);
outport8(PORT + IER, ier);
}
int TryPopChar()
{
// Save the IER and disable interrupts.
unsigned ier = inport8(PORT + IER);
outport8(PORT + IER, 0);
int result = -1;
if ( inport8(PORT + LSR) & LSR_READY )
result = inport8(PORT);
// Wait for transmitter to become empty and restore the IER.
WaitForEmptyBuffers(PORT);
outport8(PORT + IER, ier);
return result;
}
} // namespace UART
} // namespace Sortix