[RFC PATCH v2 1/4] tty: serial_mctrl_gpio: Add irqs helpers for input lines

[Janusz Uzycki <j.uzycki@xxxxxxxxxxxxxx>]

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 <j.uzycki@xxxxxxxxxxxxxx>
---

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
-- 
1.7.11.3

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