Commit 4a0ac0f5 authored by Mark Jackson's avatar Mark Jackson Committed by Greg Kroah-Hartman
Browse files

OMAP: add RS485 support 



This patch adds RS485 support to the OMAP serial driver, as
defined in:-

Documentation/devicetree/bindings/serial/rs485.txt

When a UART transmitter is connected to (eg) a RS485 driver, it is
necessary to turn the driver on/off as quickly as possible.  This is
best achieved in the serial driver itself (rather than in userspace
where the latency can be quite large).

This patch allows a GPIO pin to be defined (via DT) that controls
the enabling of the driver at the start of a message, and disables
the driver when the message has been completed.

When RS485 is disabled, the RTS pin is set to on.

Signed-off-by: default avatarMark Jackson <mpfj@newflow.co.uk>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 071eb0ff

drivers/tty/serial/omap-serial.c

+179 −0
Original line number Diff line number Diff line
@@ -40,8 +40,11 @@ 
#include <linux/pm_runtime.h>

#include <linux/of.h>

#include <linux/gpio.h>

#include <linux/of_gpio.h>

#include <linux/platform_data/serial-omap.h>



#include <dt-bindings/gpio/gpio.h>



#define OMAP_MAX_HSUART_PORTS	6



#define UART_BUILD_REVISION(x, y)	(((x) << 8) | (y))
@@ -162,6 +165,9 @@ struct uart_omap_port { 
	int			DTR_inverted;

	int			DTR_active;



	struct serial_rs485	rs485;

	int			rts_gpio;



	struct pm_qos_request	pm_qos_request;

	u32			latency;

	u32			calc_latency;
@@ -277,13 +283,42 @@ static void serial_omap_enable_ms(struct uart_port *port) 
static void serial_omap_stop_tx(struct uart_port *port)

{

	struct uart_omap_port *up = to_uart_omap_port(port);

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

	int res;



	pm_runtime_get_sync(up->dev);



	/* handle rs485 */

	if (up->rs485.flags & SER_RS485_ENABLED) {

		/* do nothing if current tx not yet completed */

		res = serial_in(up, UART_LSR) & UART_LSR_TEMT;

		if (!res)

			return;



		/* if there's no more data to send, turn off rts */

		if (uart_circ_empty(xmit)) {

			/* if rts not already disabled */

			res = (up->rs485.flags & SER_RS485_RTS_AFTER_SEND) ? 1 : 0;

			if (gpio_get_value(up->rts_gpio) != res) {

				if (up->rs485.delay_rts_after_send > 0) {

					mdelay(up->rs485.delay_rts_after_send);

				}

				gpio_set_value(up->rts_gpio, res);

			}

		}

	}



	if (up->ier & UART_IER_THRI) {

		up->ier &= ~UART_IER_THRI;

		serial_out(up, UART_IER, up->ier);

	}



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

	    !(up->rs485.flags & SER_RS485_RX_DURING_TX)) {

		up->ier = UART_IER_RLSI | UART_IER_RDI;

		serial_out(up, UART_IER, up->ier);

	}



	pm_runtime_mark_last_busy(up->dev);

	pm_runtime_put_autosuspend(up->dev);

}
@@ -346,8 +381,26 @@ static inline void serial_omap_enable_ier_thri(struct uart_omap_port *up) 
static void serial_omap_start_tx(struct uart_port *port)

{

	struct uart_omap_port *up = to_uart_omap_port(port);

	int res;



	pm_runtime_get_sync(up->dev);



	/* handle rs485 */

	if (up->rs485.flags & SER_RS485_ENABLED) {

		/* if rts not already enabled */

		res = (up->rs485.flags & SER_RS485_RTS_ON_SEND) ? 1 : 0;

		if (gpio_get_value(up->rts_gpio) != res) {

			gpio_set_value(up->rts_gpio, res);

			if (up->rs485.delay_rts_before_send > 0) {

				mdelay(up->rs485.delay_rts_before_send);

			}

		}

	}



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

	    !(up->rs485.flags & SER_RS485_RX_DURING_TX))

		serial_omap_stop_rx(port);



	serial_omap_enable_ier_thri(up);

	pm_runtime_mark_last_busy(up->dev);

	pm_runtime_put_autosuspend(up->dev);
@@ -1262,6 +1315,79 @@ static inline void serial_omap_add_console_port(struct uart_omap_port *up) 


#endif



/* Enable or disable the rs485 support */

static void

serial_omap_config_rs485(struct uart_port *port, struct serial_rs485 *rs485conf)

{

	struct uart_omap_port *up = to_uart_omap_port(port);

	unsigned long flags;

	unsigned int mode;

	int val;



	pm_runtime_get_sync(up->dev);

	spin_lock_irqsave(&up->port.lock, flags);



	up->ier &= ~(UART_IER_RLSI | UART_IER_RDI);

	serial_out(up, UART_IER, up->ier);



	/* Disable interrupts from this port */

	mode = up->ier;

	up->ier = 0;

	serial_out(up, UART_IER, 0);



	/* store new config */

	up->rs485 = *rs485conf;



	/*

	 * Just as a precaution, only allow rs485

	 * to be enabled if the gpio pin is valid

	 */

	if (gpio_is_valid(up->rts_gpio)) {

		/* enable / disable rts */

		val = (up->rs485.flags & SER_RS485_ENABLED) ?

			SER_RS485_RTS_AFTER_SEND : SER_RS485_RTS_ON_SEND;

		val = (up->rs485.flags & val) ? 1 : 0;

		gpio_set_value(up->rts_gpio, val);

	} else

		up->rs485.flags &= ~SER_RS485_ENABLED;



	/* Enable interrupts */

	up->ier = mode;

	serial_out(up, UART_IER, up->ier);



	spin_unlock_irqrestore(&up->port.lock, flags);

	pm_runtime_mark_last_busy(up->dev);

	pm_runtime_put_autosuspend(up->dev);

}



static int

serial_omap_ioctl(struct uart_port *port, unsigned int cmd, unsigned long arg)

{

	struct serial_rs485 rs485conf;



	switch (cmd) {

	case TIOCSRS485:

		if (copy_from_user(&rs485conf, (struct serial_rs485 *) arg,

					sizeof(rs485conf)))

			return -EFAULT;



		serial_omap_config_rs485(port, &rs485conf);

		break;



	case TIOCGRS485:

		if (copy_to_user((struct serial_rs485 *) arg,

					&(to_uart_omap_port(port)->rs485),

					sizeof(rs485conf)))

			return -EFAULT;

		break;



	default:

		return -ENOIOCTLCMD;

	}

	return 0;

}





static struct uart_ops serial_omap_pops = {

	.tx_empty	= serial_omap_tx_empty,

	.set_mctrl	= serial_omap_set_mctrl,
@@ -1283,6 +1409,7 @@ static struct uart_ops serial_omap_pops = { 
	.request_port	= serial_omap_request_port,

	.config_port	= serial_omap_config_port,

	.verify_port	= serial_omap_verify_port,

	.ioctl		= serial_omap_ioctl,

#ifdef CONFIG_CONSOLE_POLL

	.poll_put_char  = serial_omap_poll_put_char,

	.poll_get_char  = serial_omap_poll_get_char,
@@ -1405,6 +1532,53 @@ static struct omap_uart_port_info *of_get_uart_port_info(struct device *dev) 
	return omap_up_info;

}



static int serial_omap_probe_rs485(struct uart_omap_port *up,

				   struct device_node *np)

{

	struct serial_rs485 *rs485conf = &up->rs485;

	u32 rs485_delay[2];

	enum of_gpio_flags flags;

	int ret;



	rs485conf->flags = 0;

	up->rts_gpio = -EINVAL;



	if (!np)

		return 0;



	if (of_property_read_bool(np, "rs485-rts-active-high"))

		rs485conf->flags |= SER_RS485_RTS_ON_SEND;

	else

		rs485conf->flags |= SER_RS485_RTS_AFTER_SEND;



	/* check for tx enable gpio */

	up->rts_gpio = of_get_named_gpio_flags(np, "rts-gpio", 0, &flags);

	if (gpio_is_valid(up->rts_gpio)) {

		ret = gpio_request(up->rts_gpio, "omap-serial");

		if (ret < 0)

			return ret;

		ret = gpio_direction_output(up->rts_gpio,

					    flags & SER_RS485_RTS_AFTER_SEND);

		if (ret < 0)

			return ret;

	} else

		up->rts_gpio = -EINVAL;



	if (of_property_read_u32_array(np, "rs485-rts-delay",

				    rs485_delay, 2) == 0) {

		rs485conf->delay_rts_before_send = rs485_delay[0];

		rs485conf->delay_rts_after_send = rs485_delay[1];

	}



	if (of_property_read_bool(np, "rs485-rx-during-tx"))

		rs485conf->flags |= SER_RS485_RX_DURING_TX;



	if (of_property_read_bool(np, "linux,rs485-enabled-at-boot-time"))

		rs485conf->flags |= SER_RS485_ENABLED;



	return 0;

}



static int serial_omap_probe(struct platform_device *pdev)

{

	struct uart_omap_port	*up;
@@ -1480,6 +1654,10 @@ static int serial_omap_probe(struct platform_device *pdev) 
		goto err_port_line;

	}



	ret = serial_omap_probe_rs485(up, pdev->dev.of_node);

	if (ret < 0)

		goto err_rs485;



	sprintf(up->name, "OMAP UART%d", up->port.line);

	up->port.mapbase = mem->start;

	up->port.membase = devm_ioremap(&pdev->dev, mem->start,
@@ -1535,6 +1713,7 @@ err_add_port: 
	pm_runtime_put(&pdev->dev);

	pm_runtime_disable(&pdev->dev);

err_ioremap:

err_rs485:

err_port_line:

	dev_err(&pdev->dev, "[UART%d]: failure [%s]: %d\n",

				pdev->id, __func__, ret);

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