Commit 9be1064f authored by Daniel Golle's avatar Daniel Golle Committed by Greg Kroah-Hartman
Browse files

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: default avatarDaniel Golle <daniel@makrotopia.org>
Link: https://lore.kernel.org/r/20200221212331.GA21467@makrotopia.org


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 9fa3c4b1

drivers/tty/serial/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -1269,6 +1269,7 @@ config SERIAL_AR933X 
	tristate "AR933X serial port support"

	depends on HAVE_CLK && ATH79

	select SERIAL_CORE

	select SERIAL_MCTRL_GPIO if GPIOLIB

	help

	  If you have an Atheros AR933X SOC based board and want to use the

	  built-in UART of the SoC, say Y to this option.

drivers/tty/serial/ar933x_uart.c

+107 −6
Original line number Diff line number Diff line
@@ -13,6 +13,7 @@ 
#include <linux/console.h>

#include <linux/sysrq.h>

#include <linux/delay.h>

#include <linux/gpio/consumer.h>

#include <linux/platform_device.h>

#include <linux/of.h>

#include <linux/of_platform.h>
@@ -29,6 +30,8 @@ 


#include <asm/mach-ath79/ar933x_uart.h>



#include "serial_mctrl_gpio.h"



#define DRIVER_NAME "ar933x-uart"



#define AR933X_UART_MAX_SCALE	0xff
@@ -47,6 +50,8 @@ struct ar933x_uart_port { 
	unsigned int		min_baud;

	unsigned int		max_baud;

	struct clk		*clk;

	struct mctrl_gpios	*gpios;

	struct gpio_desc	*rts_gpiod;

};



static inline unsigned int ar933x_uart_read(struct ar933x_uart_port *up,
@@ -100,6 +105,18 @@ static inline void ar933x_uart_stop_tx_interrupt(struct ar933x_uart_port *up) 
	ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);

}



static inline void ar933x_uart_start_rx_interrupt(struct ar933x_uart_port *up)

{

	up->ier |= AR933X_UART_INT_RX_VALID;

	ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);

}



static inline void ar933x_uart_stop_rx_interrupt(struct ar933x_uart_port *up)

{

	up->ier &= ~AR933X_UART_INT_RX_VALID;

	ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);

}



static inline void ar933x_uart_putc(struct ar933x_uart_port *up, int ch)

{

	unsigned int rdata;
@@ -125,11 +142,21 @@ static unsigned int ar933x_uart_tx_empty(struct uart_port *port) 


static unsigned int ar933x_uart_get_mctrl(struct uart_port *port)

{

	return TIOCM_CAR;

	struct ar933x_uart_port *up =

		container_of(port, struct ar933x_uart_port, port);

	int ret = TIOCM_CTS | TIOCM_DSR | TIOCM_CAR;



	mctrl_gpio_get(up->gpios, &ret);



	return ret;

}



static void ar933x_uart_set_mctrl(struct uart_port *port, unsigned int mctrl)

{

	struct ar933x_uart_port *up =

		container_of(port, struct ar933x_uart_port, port);



	mctrl_gpio_set(up->gpios, mctrl);

}



static void ar933x_uart_start_tx(struct uart_port *port)
@@ -140,6 +167,37 @@ static void ar933x_uart_start_tx(struct uart_port *port) 
	ar933x_uart_start_tx_interrupt(up);

}



static void ar933x_uart_wait_tx_complete(struct ar933x_uart_port *up)

{

	unsigned int status;

	unsigned int timeout = 60000;



	/* Wait up to 60ms for the character(s) to be sent. */

	do {

		status = ar933x_uart_read(up, AR933X_UART_CS_REG);

		if (--timeout == 0)

			break;

		udelay(1);

	} while (status & AR933X_UART_CS_TX_BUSY);



	if (timeout == 0)

		dev_err(up->port.dev, "waiting for TX timed out\n");

}



static void ar933x_uart_rx_flush(struct ar933x_uart_port *up)

{

	unsigned int status;



	/* clear RX_VALID interrupt */

	ar933x_uart_write(up, AR933X_UART_INT_REG, AR933X_UART_INT_RX_VALID);



	/* remove characters from the RX FIFO */

	do {

		ar933x_uart_write(up, AR933X_UART_DATA_REG, AR933X_UART_DATA_RX_CSR);

		status = ar933x_uart_read(up, AR933X_UART_DATA_REG);

	} while (status & AR933X_UART_DATA_RX_CSR);

}



static void ar933x_uart_stop_tx(struct uart_port *port)

{

	struct ar933x_uart_port *up =
@@ -153,8 +211,7 @@ static void ar933x_uart_stop_rx(struct uart_port *port) 
	struct ar933x_uart_port *up =

		container_of(port, struct ar933x_uart_port, port);



	up->ier &= ~AR933X_UART_INT_RX_VALID;

	ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);

	ar933x_uart_stop_rx_interrupt(up);

}



static void ar933x_uart_break_ctl(struct uart_port *port, int break_state)
@@ -336,11 +393,20 @@ static void ar933x_uart_rx_chars(struct ar933x_uart_port *up) 
static void ar933x_uart_tx_chars(struct ar933x_uart_port *up)

{

	struct circ_buf *xmit = &up->port.state->xmit;

	struct serial_rs485 *rs485conf = &up->port.rs485;

	int count;

	bool half_duplex_send = false;



	if (uart_tx_stopped(&up->port))

		return;



	if ((rs485conf->flags & SER_RS485_ENABLED) &&

	    (up->port.x_char || !uart_circ_empty(xmit))) {

		ar933x_uart_stop_rx_interrupt(up);

		gpiod_set_value(up->rts_gpiod, !!(rs485conf->flags & SER_RS485_RTS_ON_SEND));

		half_duplex_send = true;

	}



	count = up->port.fifosize;

	do {

		unsigned int rdata;
@@ -368,8 +434,14 @@ static void ar933x_uart_tx_chars(struct ar933x_uart_port *up) 
	if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)

		uart_write_wakeup(&up->port);



	if (!uart_circ_empty(xmit))

	if (!uart_circ_empty(xmit)) {

		ar933x_uart_start_tx_interrupt(up);

	} else if (half_duplex_send) {

		ar933x_uart_wait_tx_complete(up);

		ar933x_uart_rx_flush(up);

		ar933x_uart_start_rx_interrupt(up);

		gpiod_set_value(up->rts_gpiod, !!(rs485conf->flags & SER_RS485_RTS_AFTER_SEND));

	}

}



static irqreturn_t ar933x_uart_interrupt(int irq, void *dev_id)
@@ -427,8 +499,7 @@ static int ar933x_uart_startup(struct uart_port *port) 
		AR933X_UART_CS_TX_READY_ORIDE | AR933X_UART_CS_RX_READY_ORIDE);



	/* Enable RX interrupts */

	up->ier = AR933X_UART_INT_RX_VALID;

	ar933x_uart_write(up, AR933X_UART_INT_EN_REG, up->ier);

	ar933x_uart_start_rx_interrupt(up);



	spin_unlock_irqrestore(&up->port.lock, flags);
@@ -511,6 +582,21 @@ static const struct uart_ops ar933x_uart_ops = { 
	.verify_port	= ar933x_uart_verify_port,

};



static int ar933x_config_rs485(struct uart_port *port,

				struct serial_rs485 *rs485conf)

{

	struct ar933x_uart_port *up =

		container_of(port, struct ar933x_uart_port, port);



	if ((rs485conf->flags & SER_RS485_ENABLED) &&

	    !up->rts_gpiod) {

		dev_err(port->dev, "RS485 needs rts-gpio\n");

		return 1;

	}

	port->rs485 = *rs485conf;

	return 0;

}



#ifdef CONFIG_SERIAL_AR933X_CONSOLE

static struct ar933x_uart_port *

ar933x_console_ports[CONFIG_SERIAL_AR933X_NR_UARTS];
@@ -680,6 +766,8 @@ static int ar933x_uart_probe(struct platform_device *pdev) 
		goto err_disable_clk;

	}



	uart_get_rs485_mode(&pdev->dev, &port->rs485);



	port->mapbase = mem_res->start;

	port->line = id;

	port->irq = irq_res->start;
@@ -690,6 +778,7 @@ static int ar933x_uart_probe(struct platform_device *pdev) 
	port->regshift = 2;

	port->fifosize = AR933X_UART_FIFO_SIZE;

	port->ops = &ar933x_uart_ops;

	port->rs485_config = ar933x_config_rs485;



	baud = ar933x_uart_get_baud(port->uartclk, AR933X_UART_MAX_SCALE, 1);

	up->min_baud = max_t(unsigned int, baud, AR933X_UART_MIN_BAUD);
@@ -697,6 +786,18 @@ static int ar933x_uart_probe(struct platform_device *pdev) 
	baud = ar933x_uart_get_baud(port->uartclk, 0, AR933X_UART_MAX_STEP);

	up->max_baud = min_t(unsigned int, baud, AR933X_UART_MAX_BAUD);



	up->gpios = mctrl_gpio_init(port, 0);

	if (IS_ERR(up->gpios) && PTR_ERR(up->gpios) != -ENOSYS)

		return PTR_ERR(up->gpios);



	up->rts_gpiod = mctrl_gpio_to_gpiod(up->gpios, UART_GPIO_RTS);



	if ((port->rs485.flags & SER_RS485_ENABLED) &&

	    !up->rts_gpiod) {

		dev_err(&pdev->dev, "lacking rts-gpio, disabling RS485\n");

		port->rs485.flags &= ~SER_RS485_ENABLED;

	}



#ifdef CONFIG_SERIAL_AR933X_CONSOLE

	ar933x_console_ports[up->port.line] = up;

#endif

CRA Git | Maintained and supported by SUSTech CRA and CCSE