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PataterBrad Mouring
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8250: Add a driver for NI 16550 UART
The National Instruments (NI) 16550 is a standard 16550 with larger FIFOs and embedded RS-485 transceiver control circuitry. This patch adds a driver that can operate this UART. Signed-off-by: Jaeden Amero <jaeden.amero@ni.com> Acked-by: Karthik Manamcheri <karthik.manamcheri@ni.com>
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‎drivers/tty/serial/8250/8250_core.c

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@@ -333,6 +333,13 @@ static const struct serial8250_config uart_config[] = {
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.fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
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.flags = UART_CAP_FIFO | UART_CAP_AFE,
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},
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[PORT_NI16550] = {
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.name = "NI 16550",
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.fifo_size = 128,
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.tx_loadsz = 128,
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.fcr = UART_FCR_ENABLE_FIFO | UART_FCR_R_TRIG_10,
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.flags = UART_CAP_FIFO | UART_CAP_AFE | UART_CAP_EFR,
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},
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};
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/* Uart divisor latch read */

‎drivers/tty/serial/8250/8250_ni16550.c

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/*
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* NI 16550 Transceiver Driver
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*
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* The National Instruments (NI) 16550 has built-in RS-485 transceiver control
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* circuitry. This driver provides the transceiver control functionality
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* for the RS-485 ports and uses the 8250 driver for the UART functionality.
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*
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* Copyright 2012 National Instruments Corporation
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the Free
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* Software Foundation; either version 2 of the License, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
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* more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc., 51
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* Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*/
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#include "8250.h"
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#include <linux/init.h>
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#include <linux/uaccess.h>
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#include <linux/device.h>
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#define NI16550_PCR_OFFSET 0x0F
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#define NI16550_PCR_RS422 0x00
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#define NI16550_PCR_ECHO_RS485 0x01
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#define NI16550_PCR_DTR_RS485 0x02
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#define NI16550_PCR_AUTO_RS485 0x03
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#define NI16550_PCR_WIRE_MODE_MASK 0x03
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#define NI16550_PCR_TXVR_ENABLE_BIT (1 << 3)
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#define NI16550_PCR_RS485_TERMINATION_BIT (1 << 6)
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static int ni16550_enable_transceivers(struct uart_port *port)
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{
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uint8_t pcr;
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dev_dbg(port->dev, ">ni16550_enable_transceivers\n");
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pcr = port->serial_in(port, NI16550_PCR_OFFSET);
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pcr |= NI16550_PCR_TXVR_ENABLE_BIT;
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dev_dbg(port->dev, "write pcr: 0x%08x\n", pcr);
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port->serial_out(port, NI16550_PCR_OFFSET, pcr);
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dev_dbg(port->dev, "<ni16550_enable_transceivers\n");
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return 0;
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}
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static int ni16550_disable_transceivers(struct uart_port *port)
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{
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uint8_t pcr;
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dev_dbg(port->dev, ">ni16550_disable_transceivers\n");
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pcr = port->serial_in(port, NI16550_PCR_OFFSET);
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pcr &= ~NI16550_PCR_TXVR_ENABLE_BIT;
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dev_dbg(port->dev, "write pcr: 0x%08x\n", pcr);
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port->serial_out(port, NI16550_PCR_OFFSET, pcr);
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dev_dbg(port->dev, "<ni16550_disable_transceivers\n");
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return 0;
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}
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static int ni16550_config_rs485(struct uart_port *port,
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struct serial_rs485 *rs485)
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{
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uint8_t pcr;
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dev_dbg(port->dev, ">ni16550_config_rs485\n");
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/* "rs485" should be given to us non-NULL. */
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BUG_ON(rs485 == NULL);
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pcr = port->serial_in(port, NI16550_PCR_OFFSET);
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pcr &= ~NI16550_PCR_WIRE_MODE_MASK;
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if (rs485->flags & SER_RS485_ENABLED) {
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/* RS-485 */
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if ((rs485->flags & SER_RS485_RX_DURING_TX) &&
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(rs485->flags & SER_RS485_RTS_ON_SEND)) {
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dev_dbg(port->dev, "Invalid 2-wire mode\n");
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return -EINVAL;
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}
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if (rs485->flags & SER_RS485_RX_DURING_TX) {
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/* Echo */
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dev_vdbg(port->dev, "2-wire DTR with echo\n");
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pcr |= NI16550_PCR_ECHO_RS485;
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} else {
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/* Auto or DTR */
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if (rs485->flags & SER_RS485_RTS_ON_SEND) {
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/* Auto */
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dev_vdbg(port->dev, "2-wire Auto\n");
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pcr |= NI16550_PCR_AUTO_RS485;
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} else {
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/* DTR-controlled */
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/* No Echo */
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dev_vdbg(port->dev, "2-wire DTR no echo\n");
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pcr |= NI16550_PCR_DTR_RS485;
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}
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}
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} else {
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/* RS-422 */
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dev_vdbg(port->dev, "4-wire\n");
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pcr |= NI16550_PCR_RS422;
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}
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dev_dbg(port->dev, "write pcr: 0x%08x\n", pcr);
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port->serial_out(port, NI16550_PCR_OFFSET, pcr);
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/* Update the cache. */
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port->rs485 = *rs485;
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dev_dbg(port->dev, "<ni16550_config_rs485\n");
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return 0;
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}
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static void
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ni16550_set_rs485_defaults(struct serial_rs485 *rs485)
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{
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rs485->flags = SER_RS485_ENABLED | SER_RS485_RTS_ON_SEND;
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}
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static struct txvr_ops ni16550_txvr_ops = {
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.enable_transceivers = ni16550_enable_transceivers,
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.disable_transceivers = ni16550_disable_transceivers,
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.config_rs485 = ni16550_config_rs485,
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};
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int ni16550_register_port(struct uart_8250_port *uart)
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{
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int line;
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dev_dbg(uart->port.dev, ">ni16550_register_port\n");
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uart->port.txvr_ops = &ni16550_txvr_ops;
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ni16550_set_rs485_defaults(&(uart->port.rs485));
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line = serial8250_register_8250_port(uart);
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dev_vdbg(uart->port.dev, "line: 0x%08x\n", line);
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if (line < 0) {
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dev_dbg(uart->port.dev, "line is less than zero\n");
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dev_dbg(uart->port.dev, "<ni16550_register_port\n");
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return -ENODEV;
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}
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dev_dbg(uart->port.dev, "<ni16550_register_port\n");
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return line;
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}
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void ni16550_unregister_port(int line)
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{
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serial8250_unregister_port(line);
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}

‎drivers/tty/serial/8250/Kconfig

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@@ -301,3 +301,9 @@ config SERIAL_8250_RT288X
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If you have a Ralink RT288x/RT305x SoC based board and want to use the
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serial port, say Y to this option. The driver can handle up to 2 serial
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ports. If unsure, say N.
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config SERIAL_8250_NI16550
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bool "NI 16550 UART support"
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depends on SERIAL_8250
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help
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This driver supports the National Instruments (NI) 16550 UART port.

‎drivers/tty/serial/8250/Makefile

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@@ -20,3 +20,4 @@ obj-$(CONFIG_SERIAL_8250_HUB6) += 8250_hub6.o
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obj-$(CONFIG_SERIAL_8250_FSL) += 8250_fsl.o
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obj-$(CONFIG_SERIAL_8250_DW) += 8250_dw.o
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obj-$(CONFIG_SERIAL_8250_EM) += 8250_em.o
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obj-$(CONFIG_SERIAL_8250_NI16550) += 8250_ni16550.o

‎include/linux/ni16550.h

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@@ -0,0 +1,31 @@
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/*
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* NI 16550 Transceiver Driver
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*
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* The National Instruments (NI) 16550 has built-in RS-485 transceiver control
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* circuitry. This driver provides the transceiver control functionality
6+
* for the RS-485 ports and uses the 8250 driver for the UART functionality.
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*
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* Copyright 2012 National Instruments Corporation
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*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the Free
12+
* Software Foundation; either version 2 of the License, or (at your option)
13+
* any later version.
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*
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* This program is distributed in the hope that it will be useful, but WITHOUT
16+
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
17+
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
18+
* more details.
19+
*
20+
* You should have received a copy of the GNU General Public License along
21+
* with this program; if not, write to the Free Software Foundation, Inc., 51
22+
* Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
23+
*/
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#ifndef _NI16550_H
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#define _NI16550_H
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int ni16550_register_port(struct uart_8250_port *uart);
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void ni16550_unregister_port(int line);
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#endif

‎include/uapi/linux/serial_core.h

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@@ -229,4 +229,7 @@
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/* SH-SCI */
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#define PORT_HSCIF 103
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/* National Instruments 16550 UART */
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#define PORT_NI16550 104
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#endif /* _UAPILINUX_SERIAL_CORE_H */

‎include/uapi/linux/serial_reg.h

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@@ -62,6 +62,7 @@
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* TI16C750: 1 16 32 56 xx xx xx xx PORT_16750
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* TI16C752: 8 16 56 60 8 16 32 56
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* Tegra: 1 4 8 14 16 8 4 1 PORT_TEGRA
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* NI 16550: 1 32 64 112 xx xx xx xx PORT_NI16550
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*/
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#define UART_FCR_R_TRIG_00 0x00
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#define UART_FCR_R_TRIG_01 0x40

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