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/*
* This file is part of the coreboot project.
*
* Copyright (C) 2003 Eric Biederman
* Copyright (C) 2006-2010 coresystems GmbH
*
* This program 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; version 2 of the License.
*
* This program 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 this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <arch/io.h>
#include <console/uart.h>
#include <uart8250.h>
#include <trace.h>
/* Should support 8250, 16450, 16550, 16550A type UARTs */
/* Nominal values only, good for the range of choices Kconfig offers for
* set of standard baudrates.
*/
#define BAUDRATE_REFCLK (115200)
#define BAUDRATE_OVERSAMPLE (1)
/* Expected character delay at 1200bps is 9ms for a working UART
* and no flow-control. Assume UART as stuck if shift register
* or FIFO takes more than 50ms per character to appear empty.
*
* Estimated that inb() from UART takes 1 microsecond.
*/
#define SINGLE_CHAR_TIMEOUT (50 * 1000)
#define FIFO_TIMEOUT (16 * SINGLE_CHAR_TIMEOUT)
static inline int uart8250_can_tx_byte(unsigned base_port)
{
return inb(base_port + UART_LSR) & UART_LSR_THRE;
}
static inline void uart8250_wait_to_tx_byte(unsigned base_port)
{
unsigned long int i = SINGLE_CHAR_TIMEOUT;
while (i-- && !uart8250_can_tx_byte(base_port));
}
static inline void uart8250_wait_until_sent(unsigned base_port)
{
unsigned long int i = FIFO_TIMEOUT;
while (i-- && !(inb(base_port + UART_LSR) & UART_LSR_TEMT));
}
void uart8250_tx_byte(unsigned base_port, unsigned char data)
{
uart8250_wait_to_tx_byte(base_port);
outb(data, base_port + UART_TBR);
}
void uart8250_tx_flush(unsigned base_port)
{
uart8250_wait_until_sent(base_port);
}
int uart8250_can_rx_byte(unsigned base_port)
{
return inb(base_port + UART_LSR) & UART_LSR_DR;
}
unsigned char uart8250_rx_byte(unsigned base_port)
{
unsigned long int i = SINGLE_CHAR_TIMEOUT;
while (i-- && !uart8250_can_rx_byte(base_port));
if (i)
return inb(base_port + UART_RBR);
else
return 0x0;
}
void uart8250_init(unsigned base_port, unsigned divisor)
{
DISABLE_TRACE;
/* Disable interrupts */
outb(0x0, base_port + UART_IER);
/* Enable FIFOs */
outb(UART_FCR_FIFO_EN, base_port + UART_FCR);
/* assert DTR and RTS so the other end is happy */
outb(UART_MCR_DTR | UART_MCR_RTS, base_port + UART_MCR);
/* DLAB on */
outb(UART_LCR_DLAB | CONFIG_TTYS0_LCS, base_port + UART_LCR);
/* Set Baud Rate Divisor. 12 ==> 9600 Baud */
outb(divisor & 0xFF, base_port + UART_DLL);
outb((divisor >> 8) & 0xFF, base_port + UART_DLM);
/* Set to 3 for 8N1 */
outb(CONFIG_TTYS0_LCS, base_port + UART_LCR);
ENABLE_TRACE;
}
void uart_init(void)
{
unsigned int div;
div = uart_baudrate_divisor(default_baudrate(), BAUDRATE_REFCLK,
BAUDRATE_OVERSAMPLE);
uart8250_init(CONFIG_TTYS0_BASE, div);
}
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