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: Mark Jackson <mpfj@xxxxxxxxxxxxx>
---
Changes in v2:
- Fix incorrect logic in serial_omap_config_rs485()
drivers/tty/serial/omap-serial.c | 178 ++++++++++++++++++++++++++++++++++++++
1 file changed, 178 insertions(+)
diff --git a/drivers/tty/serial/omap-serial.c b/drivers/tty/serial/omap-serial.c
index b6d1728..d538329 100644
--- a/drivers/tty/serial/omap-serial.c
+++ b/drivers/tty/serial/omap-serial.c
@@ -40,9 +40,12 @@
#include <linux/pm_runtime.h>
#include <linux/of.h>
#include <linux/gpio.h>
+#include <linux/of_gpio.h>
#include <linux/pinctrl/consumer.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))
@@ -156,6 +159,9 @@ 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;
@@ -272,13 +278,42 @@ 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);
}
@@ -340,8 +375,26 @@ 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);
@@ -1254,6 +1307,78 @@ 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,
@@ -1275,6 +1400,7 @@ 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,
@@ -1395,6 +1521,53 @@ 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;
@@ -1468,6 +1641,10 @@ 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;
+
up->pins = devm_pinctrl_get_select_default(&pdev->dev);
if (IS_ERR(up->pins)) {
dev_warn(&pdev->dev, "did not get pins for uart%i error: %li\n",
@@ -1529,6 +1706,7 @@ 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);
--
1.7.9.5
--
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