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-rw-r--r--Documentation/ABI/testing/sysfs-tty9
-rw-r--r--drivers/tty/serial/serial_core.c70
-rw-r--r--include/linux/serial_core.h3
3 files changed, 80 insertions, 2 deletions
diff --git a/Documentation/ABI/testing/sysfs-tty b/Documentation/ABI/testing/sysfs-tty
index 9eb3c2b6b040..441105a75d1f 100644
--- a/Documentation/ABI/testing/sysfs-tty
+++ b/Documentation/ABI/testing/sysfs-tty
@@ -154,3 +154,12 @@ Description:
device specification. For example, when user sets 7bytes on
16550A, which has 1/4/8/14 bytes trigger, the RX trigger is
automatically changed to 4 bytes.
+
+What: /sys/class/tty/ttyS0/pps_4wire
+Date: September 2018
+Contact: Steve Sakoman <steve@sakoman.com>
+Description:
+ Shows/sets "4 wire" mode for the PPS input to the serial driver.
+ For fully implemented serial ports PPS is normally provided
+ on the DCD line. For partial "4 wire" implementations CTS is
+ used instead of DCD.
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 80bb56facfb6..ed0133395cc7 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -2664,6 +2664,57 @@ static ssize_t uart_get_attr_iomem_reg_shift(struct device *dev,
return snprintf(buf, PAGE_SIZE, "%d\n", tmp.iomem_reg_shift);
}
+static ssize_t pps_4wire_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct tty_port *port = dev_get_drvdata(dev);
+ struct uart_state *state = container_of(port, struct uart_state, port);
+ struct uart_port *uport;
+ int mode = 0;
+
+ mutex_lock(&port->mutex);
+ uport = uart_port_check(state);
+ if (!uport)
+ goto out;
+
+ mode = uport->pps_4wire;
+
+out:
+ mutex_unlock(&port->mutex);
+ return sprintf(buf, mode ? "yes\n" : "no\n");
+}
+
+static ssize_t pps_4wire_store(struct device *dev,
+ struct device_attribute *attr, const char *buf, size_t count)
+{
+ struct tty_port *port = dev_get_drvdata(dev);
+ struct uart_state *state = container_of(port, struct uart_state, port);
+ struct uart_port *uport;
+ bool mode;
+ int ret;
+
+ if (!count)
+ return -EINVAL;
+
+ ret = kstrtobool(buf, &mode);
+ if (ret < 0)
+ return ret;
+
+ mutex_lock(&port->mutex);
+ uport = uart_port_check(state);
+ if (!uport)
+ goto out;
+
+ spin_lock_irq(&uport->lock);
+ uport->pps_4wire = mode;
+ spin_unlock_irq(&uport->lock);
+
+out:
+ mutex_unlock(&port->mutex);
+ return count;
+}
+static DEVICE_ATTR_RW(pps_4wire);
+
static DEVICE_ATTR(type, S_IRUSR | S_IRGRP, uart_get_attr_type, NULL);
static DEVICE_ATTR(line, S_IRUSR | S_IRGRP, uart_get_attr_line, NULL);
static DEVICE_ATTR(port, S_IRUSR | S_IRGRP, uart_get_attr_port, NULL);
@@ -2692,6 +2743,7 @@ static struct attribute *tty_dev_attrs[] = {
&dev_attr_io_type.attr,
&dev_attr_iomem_base.attr,
&dev_attr_iomem_reg_shift.attr,
+ &dev_attr_pps_4wire.attr,
NULL,
};
@@ -2748,6 +2800,9 @@ int uart_add_one_port(struct uart_driver *drv, struct uart_port *uport)
goto out;
}
+ /* assert that pps handling is done via DCD as default */
+ uport->pps_4wire = 0;
+
/*
* If this port is a console, then the spinlock is already
* initialised.
@@ -2923,7 +2978,7 @@ void uart_handle_dcd_change(struct uart_port *uport, unsigned int status)
lockdep_assert_held_once(&uport->lock);
- if (tty) {
+ if (tty && !uport->pps_4wire) {
ld = tty_ldisc_ref(tty);
if (ld) {
if (ld->ops->dcd_change)
@@ -2952,8 +3007,21 @@ EXPORT_SYMBOL_GPL(uart_handle_dcd_change);
*/
void uart_handle_cts_change(struct uart_port *uport, unsigned int status)
{
+ struct tty_port *port = &uport->state->port;
+ struct tty_struct *tty = port->tty;
+ struct tty_ldisc *ld;
+
lockdep_assert_held_once(&uport->lock);
+ if (tty && uport->pps_4wire) {
+ ld = tty_ldisc_ref(tty);
+ if (ld) {
+ if (ld->ops->dcd_change)
+ ld->ops->dcd_change(tty, status);
+ tty_ldisc_deref(ld);
+ }
+ }
+
uport->icount.cts++;
if (uart_softcts_mode(uport)) {
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 406edae44ca3..079793e5d3fa 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -255,7 +255,8 @@ struct uart_port {
struct device *dev; /* parent device */
unsigned char hub6; /* this should be in the 8250 driver */
unsigned char suspended;
- unsigned char unused[2];
+ unsigned char pps_4wire; /* CTS instead of DCD */
+ unsigned char unused;
const char *name; /* port name */
struct attribute_group *attr_group; /* port specific attributes */
const struct attribute_group **tty_groups; /* all attributes (serial core use only) */