/*
* Copyright (C) 2014 Michael Brown <mbrown@fensystems.co.uk>.
*
* 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; either version 2 of the
* License, or any later version.
*
* 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 Street, Fifth Floor, Boston, MA
* 02110-1301, USA.
*
* You can also choose to distribute this program under the terms of
* the Unmodified Binary Distribution Licence (as given in the file
* COPYING.UBDL), provided that you have satisfied its requirements.
*/
FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
/** @file
*
* 16550-compatible UART
*
*/
#include <unistd.h>
#include <errno.h>
#include <ipxe/uart.h>
/** Timeout for transmit holding register to become empty */
#define UART_THRE_TIMEOUT_MS 100
/** Timeout for transmitter to become empty */
#define UART_TEMT_TIMEOUT_MS 1000
/**
* Transmit data
*
* @v uart UART
* @v data Data
*/
void uart_transmit ( struct uart *uart, uint8_t data ) {
unsigned int i;
uint8_t lsr;
/* Wait for transmitter holding register to become empty */
for ( i = 0 ; i < UART_THRE_TIMEOUT_MS ; i++ ) {
lsr = uart_read ( uart, UART_LSR );
if ( lsr & UART_LSR_THRE )
break;
mdelay ( 1 );
}
/* Transmit data (even if we timed out) */
uart_write ( uart, UART_THR, data );
}
/**
* Flush data
*
* @v uart UART
*/
void uart_flush ( struct uart *uart ) {
unsigned int i;
uint8_t lsr;
/* Wait for transmitter and receiver to become empty */
for ( i = 0 ; i < UART_TEMT_TIMEOUT_MS ; i++ ) {
uart_read ( uart, UART_RBR );
lsr = uart_read ( uart, UART_LSR );
if ( ( lsr & UART_LSR_TEMT ) && ! ( lsr & UART_LSR_DR ) )
break;
}
}
/**
* Check for existence of UART
*
* @v uart UART
* @ret rc Return status code
*/
int uart_exists ( struct uart *uart ) {
/* Fail if no UART port is defined */
if ( ! uart->base )
return -ENODEV;
/* Fail if UART scratch register seems not to be present */
uart_write ( uart, UART_SCR, 0x18 );
if ( uart_read ( uart, UART_SCR ) != 0x18 )
return -ENODEV;
uart_write ( uart, UART_SCR, 0xae );
if ( uart_read ( uart, UART_SCR ) != 0xae )
return -ENODEV;
return 0;
}
/**
* Initialise UART
*
* @v uart UART
* @v baud Baud rate, or zero to leave unchanged
* @v lcr Line control register value, or zero to leave unchanged
* @ret rc Return status code
*/
int uart_init ( struct uart *uart, unsigned int baud, uint8_t lcr ) {
uint8_t dlm;
uint8_t dll;
int rc;
/* Check for existence of UART */
if ( ( rc = uart_exists ( uart ) ) != 0 )
return rc;
/* Configure divisor and line control register, if applicable */
if ( ! lcr )
lcr = uart_read ( uart, UART_LCR );
uart->lcr = lcr;
uart_write ( uart, UART_LCR, ( lcr | UART_LCR_DLAB ) );
if ( baud ) {
uart->divisor = ( UART_MAX_BAUD / baud );
dlm = ( ( uart->divisor >> 8 ) & 0xff );
dll = ( ( uart->divisor >> 0 ) & 0xff );
uart_write ( uart, UART_DLM, dlm );
uart_write ( uart, UART_DLL, dll );
} else {
dlm = uart_read ( uart, UART_DLM );
dll = uart_read ( uart, UART_DLL );
uart->divisor = ( ( dlm << 8 ) | dll );
}
uart_write ( uart, UART_LCR, ( lcr & ~UART_LCR_DLAB ) );
/* Disable interrupts */
uart_write ( uart, UART_IER, 0 );
/* Enable FIFOs */
uart_write ( uart, UART_FCR, UART_FCR_FE );
/* Assert DTR and RTS */
uart_write ( uart, UART_MCR, ( UART_MCR_DTR | UART_MCR_RTS ) );
/* Flush any stale data */
uart_flush ( uart );
return 0;
}
