A driver using mctrl_gpio called gpiod_get_direction() to check if
gpio is input line. However .get_direction callback is not available
for all platforms. The patch allows to avoid the function.
The patch introduces the following helpers:
- mctrl_gpio_request_irqs
- mctrl_gpio_free_irqs
- mctrl_gpio_enable_ms
- mctrl_gpio_disable_ms
They allow to:
- simplify drivers which use mctrl_gpio
- hide irq table in mctrl_gpio
- use default irq handler for gpios
- better separate code for gpio modem lines from uart's code
In addition mctrl_gpio_init() has been renamed to mctrl_gpio_init_dt()
to focus DT usage. Also mctrl_gpio_init_dt() initializes irq table for
gpios now and passes struct uart_port into struct mctrl_gpios.
This resulted in changed mctrl_gpio_init_dt() parameter.
It also requires port->dev is set before the function is called.

There were also fixed:
- irq = 0 means invalid/unused (-EINVAL no more used)
- mctrl_gpio_request_irqs() doesn't use negative enum value
   if request_irq() failed. It just calls mctrl_gpio_free_irqs().

The mctrl_gpio_is_gpio() inline function is under discussion
and likely it can replace exported mctrl_gpio_to_gpiod() function.

IRQ_NOAUTOEN setting and request_irq() order was not commented
but it looks right according to other drivers.

Signed-off-by: Janusz Uzycki <redacted>
---

The patch requires to update the drivers which use mctrl_gpio:
- atmel_serial
- mxs-auart
- clps711x

Changes since RFC v1:
  - patch renamed from:
    ("serial: mctrl-gpio: Add irqs helpers for input lines")
    to:
    ("tty: serial_mctrl_gpio: Add irqs helpers for input lines")
  - mctrl_gpio_request_irqs: changed mctrl_gpio_free_irqs() and
    dev_err() order to make debug easier
  - added patches for atmel_serial and clps711x serial drivers

The patch applies to next (3.19.0-rc2) and was tested with mxs-auart
using kernel 3.14 and 3.18. It wasn't tested on the next (only compiled).

The patchset delivers patches for mxs-auart, atmel_serial and clps711x.
atmel_serial and clps711x were not tested - only compile tests were done.

---
  drivers/tty/serial/serial_mctrl_gpio.c | 109 ++++++++++++++++++++++++++++++++-
  drivers/tty/serial/serial_mctrl_gpio.h |  59 +++++++++++++++++-
  2 files changed, 163 insertions(+), 5 deletions(-)

diff --git a/drivers/tty/serial/serial_mctrl_gpio.c b/drivers/tty/serial/serial_mctrl_gpio.c
index a38596c..215b15c 100644
--- a/drivers/tty/serial/serial_mctrl_gpio.c
+++ b/drivers/tty/serial/serial_mctrl_gpio.c

@@ -19,11 +19,15 @@
  #include <linux/device.h>
  #include <linux/gpio/consumer.h>
  #include <linux/termios.h>
+#include <linux/irq.h>
  
  #include "serial_mctrl_gpio.h"
  
  struct mctrl_gpios {
+	struct uart_port *port;
  	struct gpio_desc *gpio[UART_GPIO_MAX];
+	int irq[UART_GPIO_MAX];
+	unsigned int mctrl_prev;
  };
  
  static const struct {

@@ -72,6 +76,12 @@ struct gpio_desc *mctrl_gpio_to_gpiod(struct mctrl_gpios *gpios,
  }
  EXPORT_SYMBOL_GPL(mctrl_gpio_to_gpiod);
  
+inline
+bool mctrl_gpio_is_gpio(struct mctrl_gpios *gpios, enum mctrl_gpio_idx gidx)
+{
+	return !IS_ERR_OR_NULL(gpios->gpio[gidx]);
+}
+
  unsigned int mctrl_gpio_get(struct mctrl_gpios *gpios, unsigned int *mctrl)
  {
  	enum mctrl_gpio_idx i;

@@ -96,8 +106,9 @@ unsigned int mctrl_gpio_get(struct mctrl_gpios *gpios, unsigned int *mctrl)
  }
  EXPORT_SYMBOL_GPL(mctrl_gpio_get);
  
-struct mctrl_gpios *mctrl_gpio_init(struct device *dev, unsigned int idx)
+struct mctrl_gpios *mctrl_gpio_init_dt(struct uart_port *port, unsigned int idx)
  {
+	struct device *dev = port->dev;
  	struct mctrl_gpios *gpios;
  	enum mctrl_gpio_idx i;
  	int err;

@@ -106,6 +117,7 @@ struct mctrl_gpios *mctrl_gpio_init(struct device *dev, unsigned int idx)
  	if (!gpios)
  		return ERR_PTR(-ENOMEM);
  
+	gpios->port = port;
  	for (i = 0; i < UART_GPIO_MAX; i++) {
  		gpios->gpio[i] = devm_gpiod_get_index(dev,
  						      mctrl_gpios_desc[i].name,

@@ -128,11 +140,13 @@ struct mctrl_gpios *mctrl_gpio_init(struct device *dev, unsigned int idx)
  			devm_gpiod_put(dev, gpios->gpio[i]);
  			gpios->gpio[i] = NULL;
  		}
+		if (gpios->gpio[i] && !mctrl_gpios_desc[i].dir_out)
+			gpios->irq[i] = gpiod_to_irq(gpios->gpio[i]);
  	}
  
  	return gpios;
  }
-EXPORT_SYMBOL_GPL(mctrl_gpio_init);
+EXPORT_SYMBOL_GPL(mctrl_gpio_init_dt);
  
  void mctrl_gpio_free(struct device *dev, struct mctrl_gpios *gpios)
  {

@@ -147,3 +161,94 @@ void mctrl_gpio_free(struct device *dev, struct mctrl_gpios *gpios)
  	devm_kfree(dev, gpios);
  }
  EXPORT_SYMBOL_GPL(mctrl_gpio_free);
+
+/*
+ * Dealing with GPIO interrupt
+ */
+#define MCTRL_ANY_DELTA        (TIOCM_RI | TIOCM_DSR | TIOCM_CD | TIOCM_CTS)
+static irqreturn_t mctrl_gpio_irq_handle(int irq, void *context)
+{
+	struct mctrl_gpios *gpios = context;
+	struct uart_port *port = gpios->port;
+	u32 mctrl = gpios->mctrl_prev;
+	u32 mctrl_diff;
+
+	mctrl_gpio_get(gpios, &mctrl);
+
+	mctrl_diff = mctrl ^ gpios->mctrl_prev;
+	gpios->mctrl_prev = mctrl;
+	if (mctrl_diff & MCTRL_ANY_DELTA && port->state != NULL) {
+		if (mctrl_diff & TIOCM_RI)
+			port->icount.rng++;
+		if (mctrl_diff & TIOCM_DSR)
+			port->icount.dsr++;
+		if (mctrl_diff & TIOCM_CD)
+			uart_handle_dcd_change(port, mctrl & TIOCM_CD);
+		if (mctrl_diff & TIOCM_CTS)
+			uart_handle_cts_change(port, mctrl & TIOCM_CTS);
+
+		wake_up_interruptible(&port->state->port.delta_msr_wait);
+	}
+
+	return IRQ_HANDLED;
+}
+
+int mctrl_gpio_request_irqs(struct mctrl_gpios *gpios)
+{
+	struct uart_port *port = gpios->port;
+	int *irq = gpios->irq;
+	enum mctrl_gpio_idx i;
+	int err = 0;
+
+	for (i = 0; i < UART_GPIO_MAX; i++) {
+		if (irq[i] <= 0)
+			continue;
+
+		irq_set_status_flags(irq[i], IRQ_NOAUTOEN);
+		err = request_irq(irq[i], mctrl_gpio_irq_handle,
+				  IRQ_TYPE_EDGE_BOTH,
+				  dev_name(port->dev), gpios);
+		if (err) {
+			dev_err(port->dev, "%s: Can't get %d irq\n",
+				__func__, irq[i]);
+			mctrl_gpio_free_irqs(gpios);
+			break;
+		}
+	}
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(mctrl_gpio_request_irqs);
+
+void mctrl_gpio_free_irqs(struct mctrl_gpios *gpios)
+{
+	enum mctrl_gpio_idx i;
+
+	for (i = 0; i < UART_GPIO_MAX; i++)
+		if (gpios->irq[i] > 0)
+			free_irq(gpios->irq[i], gpios);
+}
+EXPORT_SYMBOL_GPL(mctrl_gpio_free_irqs);
+
+void mctrl_gpio_enable_ms(struct mctrl_gpios *gpios)
+{
+	enum mctrl_gpio_idx i;
+
+	/* get initial status of modem lines GPIOs */
+	mctrl_gpio_get(gpios, &gpios->mctrl_prev);
+
+	for (i = 0; i < UART_GPIO_MAX; i++)
+		if (gpios->irq[i] > 0)
+			enable_irq(gpios->irq[i]);
+}
+EXPORT_SYMBOL_GPL(mctrl_gpio_enable_ms);
+
+void mctrl_gpio_disable_ms(struct mctrl_gpios *gpios)
+{
+	enum mctrl_gpio_idx i;
+
+	for (i = 0; i < UART_GPIO_MAX; i++)
+		if (gpios->irq[i] > 0)
+			disable_irq(gpios->irq[i]);
+}
+EXPORT_SYMBOL_GPL(mctrl_gpio_disable_ms);

diff --git a/drivers/tty/serial/serial_mctrl_gpio.h b/drivers/tty/serial/serial_mctrl_gpio.h
index 400ba04..13ba3f4 100644
--- a/drivers/tty/serial/serial_mctrl_gpio.h
+++ b/drivers/tty/serial/serial_mctrl_gpio.h

@@ -21,6 +21,7 @@
  #include <linux/err.h>
  #include <linux/device.h>
  #include <linux/gpio/consumer.h>
+#include <linux/serial_core.h>
  
  enum mctrl_gpio_idx {
  	UART_GPIO_CTS,

@@ -40,6 +41,13 @@ enum mctrl_gpio_idx {
   */
  struct mctrl_gpios;
  
+/*
+ * Return true if gidx is GPIO line, otherwise false.
+ * It assumes that gpios is allocated and not NULL.
+ */
+inline
+bool mctrl_gpio_is_gpio(struct mctrl_gpios *gpios, enum mctrl_gpio_idx gidx);
+
  #ifdef CONFIG_GPIOLIB
  
  /*

@@ -60,12 +68,13 @@ struct gpio_desc *mctrl_gpio_to_gpiod(struct mctrl_gpios *gpios,
  				      enum mctrl_gpio_idx gidx);
  
  /*
- * Request and set direction of modem control lines GPIOs.
+ * Request and set direction of modem control lines GPIOs. DT is used.
+ * Initialize irq table for GPIOs.
   * devm_* functions are used, so there's no need to call mctrl_gpio_free().
   * Returns a pointer to the allocated mctrl structure if ok, -ENOMEM on
   * allocation error.
   */
-struct mctrl_gpios *mctrl_gpio_init(struct device *dev, unsigned int idx);
+struct mctrl_gpios *mctrl_gpio_init_dt(struct uart_port *port, unsigned int idx);
  
  /*
   * Free the mctrl_gpios structure.

@@ -74,6 +83,28 @@ struct mctrl_gpios *mctrl_gpio_init(struct device *dev, unsigned int idx);
   */
  void mctrl_gpio_free(struct device *dev, struct mctrl_gpios *gpios);
  
+/*
+ * Request irqs for input lines GPIOs. The irqs are set disabled
+ * and triggered on both edges.
+ * Returns zero if OK, otherwise an error code.
+ */
+int mctrl_gpio_request_irqs(struct mctrl_gpios *gpios);
+
+/*
+ * Free irqs for input lines GPIOs.
+ */
+void mctrl_gpio_free_irqs(struct mctrl_gpios *gpios);
+
+/*
+ * Disable modem status interrupts assigned to GPIOs
+ */
+void mctrl_gpio_enable_ms(struct mctrl_gpios *gpios);
+
+/*
+ * Enable modem status interrupts assigned to GPIOs
+ */
+void mctrl_gpio_disable_ms(struct mctrl_gpios *gpios);
+
  #else /* GPIOLIB */
  
  static inline

@@ -95,7 +126,7 @@ struct gpio_desc *mctrl_gpio_to_gpiod(struct mctrl_gpios *gpios,
  }
  
  static inline
-struct mctrl_gpios *mctrl_gpio_init(struct device *dev, unsigned int idx)
+struct mctrl_gpios *mctrl_gpio_init_dt(struct uart_port *port, unsigned int idx)
  {
  	return ERR_PTR(-ENOSYS);
  }

@@ -105,6 +136,28 @@ void mctrl_gpio_free(struct device *dev, struct mctrl_gpios *gpios)
  {
  }
  
+static inline
+int mctrl_gpio_request_irqs(struct mctrl_gpios *gpios)
+{
+	/*return -ENOTSUP;*/
+	return 0;
+}
+
+static inline
+void mctrl_gpio_free_irqs(struct mctrl_gpios *gpios)
+{
+}
+
+static inline
+void mctrl_gpio_enable_ms(struct mctrl_gpios *gpios)
+{
+}
+
+static inline
+void mctrl_gpio_disable_ms(struct mctrl_gpios *gpios)
+{
+}
+
  #endif /* GPIOLIB */
  
  #endif