serial: ar933x_uart: add RS485 support
Emulate half-duplex operation and use mctrl_gpio to add support for RS485 tranceiver with transmit/receive switch hooked to RTS GPIO line. This is needed to make use of the RS485 port found on Teltonika RUT955. Signed-off-by: Daniel Golle <daniel@makrotopia.org> Link: https://lore.kernel.org/r/20200221212331.GA21467@makrotopia.org Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Daniel Golle
Greg Kroah-Hartman
Родитель
9fa3c4b1fa
Коммит
9be1064fe5
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@ -1269,6 +1269,7 @@ config SERIAL_AR933X
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tristate "AR933X serial port support"
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depends on HAVE_CLK && ATH79
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select SERIAL_CORE
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select SERIAL_MCTRL_GPIO if GPIOLIB
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help
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If you have an Atheros AR933X SOC based board and want to use the
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built-in UART of the SoC, say Y to this option.
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@ -13,6 +13,7 @@
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#include <linux/console.h>
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#include <linux/sysrq.h>
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#include <linux/delay.h>
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#include <linux/gpio/consumer.h>
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#include <linux/platform_device.h>
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#include <linux/of.h>
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#include <linux/of_platform.h>
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@ -29,6 +30,8 @@
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#include <asm/mach-ath79/ar933x_uart.h>
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#include "serial_mctrl_gpio.h"
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#define DRIVER_NAME "ar933x-uart"
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#define AR933X_UART_MAX_SCALE 0xff
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@ -47,6 +50,8 @@ struct ar933x_uart_port {
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unsigned int min_baud;
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unsigned int max_baud;
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struct clk *clk;
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struct mctrl_gpios *gpios;
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struct gpio_desc *rts_gpiod;
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};
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static inline unsigned int ar933x_uart_read(struct ar933x_uart_port *up,
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@ -100,6 +105,18 @@ static inline void ar933x_uart_stop_tx_interrupt(struct ar933x_uart_port *up)
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ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
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}
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static inline void ar933x_uart_start_rx_interrupt(struct ar933x_uart_port *up)
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{
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up->ier |= AR933X_UART_INT_RX_VALID;
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ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
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}
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static inline void ar933x_uart_stop_rx_interrupt(struct ar933x_uart_port *up)
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{
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up->ier &= ~AR933X_UART_INT_RX_VALID;
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ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
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}
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static inline void ar933x_uart_putc(struct ar933x_uart_port *up, int ch)
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{
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unsigned int rdata;
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@ -125,11 +142,21 @@ static unsigned int ar933x_uart_tx_empty(struct uart_port *port)
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static unsigned int ar933x_uart_get_mctrl(struct uart_port *port)
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{
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return TIOCM_CAR;
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struct ar933x_uart_port *up =
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container_of(port, struct ar933x_uart_port, port);
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int ret = TIOCM_CTS | TIOCM_DSR | TIOCM_CAR;
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mctrl_gpio_get(up->gpios, &ret);
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return ret;
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}
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static void ar933x_uart_set_mctrl(struct uart_port *port, unsigned int mctrl)
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{
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struct ar933x_uart_port *up =
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container_of(port, struct ar933x_uart_port, port);
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mctrl_gpio_set(up->gpios, mctrl);
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}
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static void ar933x_uart_start_tx(struct uart_port *port)
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@ -140,6 +167,37 @@ static void ar933x_uart_start_tx(struct uart_port *port)
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ar933x_uart_start_tx_interrupt(up);
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}
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static void ar933x_uart_wait_tx_complete(struct ar933x_uart_port *up)
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{
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unsigned int status;
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unsigned int timeout = 60000;
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/* Wait up to 60ms for the character(s) to be sent. */
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do {
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status = ar933x_uart_read(up, AR933X_UART_CS_REG);
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if (--timeout == 0)
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break;
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udelay(1);
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} while (status & AR933X_UART_CS_TX_BUSY);
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if (timeout == 0)
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dev_err(up->port.dev, "waiting for TX timed out\n");
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}
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static void ar933x_uart_rx_flush(struct ar933x_uart_port *up)
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{
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unsigned int status;
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/* clear RX_VALID interrupt */
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ar933x_uart_write(up, AR933X_UART_INT_REG, AR933X_UART_INT_RX_VALID);
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/* remove characters from the RX FIFO */
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do {
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ar933x_uart_write(up, AR933X_UART_DATA_REG, AR933X_UART_DATA_RX_CSR);
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status = ar933x_uart_read(up, AR933X_UART_DATA_REG);
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} while (status & AR933X_UART_DATA_RX_CSR);
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}
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static void ar933x_uart_stop_tx(struct uart_port *port)
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{
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struct ar933x_uart_port *up =
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@ -153,8 +211,7 @@ static void ar933x_uart_stop_rx(struct uart_port *port)
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struct ar933x_uart_port *up =
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container_of(port, struct ar933x_uart_port, port);
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up->ier &= ~AR933X_UART_INT_RX_VALID;
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ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
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ar933x_uart_stop_rx_interrupt(up);
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}
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static void ar933x_uart_break_ctl(struct uart_port *port, int break_state)
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@ -336,11 +393,20 @@ static void ar933x_uart_rx_chars(struct ar933x_uart_port *up)
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static void ar933x_uart_tx_chars(struct ar933x_uart_port *up)
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{
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struct circ_buf *xmit = &up->port.state->xmit;
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struct serial_rs485 *rs485conf = &up->port.rs485;
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int count;
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bool half_duplex_send = false;
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if (uart_tx_stopped(&up->port))
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return;
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if ((rs485conf->flags & SER_RS485_ENABLED) &&
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(up->port.x_char || !uart_circ_empty(xmit))) {
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ar933x_uart_stop_rx_interrupt(up);
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gpiod_set_value(up->rts_gpiod, !!(rs485conf->flags & SER_RS485_RTS_ON_SEND));
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half_duplex_send = true;
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}
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count = up->port.fifosize;
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do {
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unsigned int rdata;
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@ -368,8 +434,14 @@ static void ar933x_uart_tx_chars(struct ar933x_uart_port *up)
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if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
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uart_write_wakeup(&up->port);
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if (!uart_circ_empty(xmit))
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if (!uart_circ_empty(xmit)) {
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ar933x_uart_start_tx_interrupt(up);
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} else if (half_duplex_send) {
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ar933x_uart_wait_tx_complete(up);
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ar933x_uart_rx_flush(up);
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ar933x_uart_start_rx_interrupt(up);
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gpiod_set_value(up->rts_gpiod, !!(rs485conf->flags & SER_RS485_RTS_AFTER_SEND));
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}
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}
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static irqreturn_t ar933x_uart_interrupt(int irq, void *dev_id)
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@ -427,8 +499,7 @@ static int ar933x_uart_startup(struct uart_port *port)
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AR933X_UART_CS_TX_READY_ORIDE | AR933X_UART_CS_RX_READY_ORIDE);
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/* Enable RX interrupts */
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up->ier = AR933X_UART_INT_RX_VALID;
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ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);
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ar933x_uart_start_rx_interrupt(up);
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spin_unlock_irqrestore(&up->port.lock, flags);
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@ -511,6 +582,21 @@ static const struct uart_ops ar933x_uart_ops = {
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.verify_port = ar933x_uart_verify_port,
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};
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static int ar933x_config_rs485(struct uart_port *port,
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struct serial_rs485 *rs485conf)
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{
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struct ar933x_uart_port *up =
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container_of(port, struct ar933x_uart_port, port);
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if ((rs485conf->flags & SER_RS485_ENABLED) &&
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!up->rts_gpiod) {
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dev_err(port->dev, "RS485 needs rts-gpio\n");
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return 1;
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}
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port->rs485 = *rs485conf;
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return 0;
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}
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#ifdef CONFIG_SERIAL_AR933X_CONSOLE
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static struct ar933x_uart_port *
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ar933x_console_ports[CONFIG_SERIAL_AR933X_NR_UARTS];
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@ -680,6 +766,8 @@ static int ar933x_uart_probe(struct platform_device *pdev)
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goto err_disable_clk;
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}
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uart_get_rs485_mode(&pdev->dev, &port->rs485);
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port->mapbase = mem_res->start;
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port->line = id;
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port->irq = irq_res->start;
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@ -690,6 +778,7 @@ static int ar933x_uart_probe(struct platform_device *pdev)
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port->regshift = 2;
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port->fifosize = AR933X_UART_FIFO_SIZE;
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port->ops = &ar933x_uart_ops;
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port->rs485_config = ar933x_config_rs485;
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baud = ar933x_uart_get_baud(port->uartclk, AR933X_UART_MAX_SCALE, 1);
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up->min_baud = max_t(unsigned int, baud, AR933X_UART_MIN_BAUD);
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@ -697,6 +786,18 @@ static int ar933x_uart_probe(struct platform_device *pdev)
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baud = ar933x_uart_get_baud(port->uartclk, 0, AR933X_UART_MAX_STEP);
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up->max_baud = min_t(unsigned int, baud, AR933X_UART_MAX_BAUD);
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up->gpios = mctrl_gpio_init(port, 0);
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if (IS_ERR(up->gpios) && PTR_ERR(up->gpios) != -ENOSYS)
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return PTR_ERR(up->gpios);
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up->rts_gpiod = mctrl_gpio_to_gpiod(up->gpios, UART_GPIO_RTS);
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if ((port->rs485.flags & SER_RS485_ENABLED) &&
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!up->rts_gpiod) {
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dev_err(&pdev->dev, "lacking rts-gpio, disabling RS485\n");
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port->rs485.flags &= ~SER_RS485_ENABLED;
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}
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#ifdef CONFIG_SERIAL_AR933X_CONSOLE
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ar933x_console_ports[up->port.line] = up;
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#endif
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