serial: mctrl_gpio: implement interrupt handling

This allows to reduce the per-driver boiler plate considerably.

Signed-off-by: Uwe Kleine-König <[e-mail]>
Reviewed-by: Nicolas Ferre <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/serial/driver

···
 
 Some helpers are provided in order to set/get modem control lines via GPIO.
 
-mctrl_gpio_init(dev, idx):
+mctrl_gpio_init(port, idx):
 	This will get the {cts,rts,...}-gpios from device tree if they are
 	present and request them, set direction etc, and return an
 	allocated structure. devm_* functions are used, so there's no need
 	to call mctrl_gpio_free().
+	As this sets up the irq handling make sure to not handle changes to the
+	gpio input lines in your driver, too.
 
 mctrl_gpio_free(dev, gpios):
 	This will free the requested gpios in mctrl_gpio_init().
···
 
 mctrl_gpio_get(gpios, mctrl):
 	This will update mctrl with the gpios values.
+
+mctrl_gpio_enable_ms(gpios):
+	Enables irqs and handling of changes to the ms lines.
+
+mctrl_gpio_disable_ms(gpios):
+	Disables irqs and handling of changes to the ms lines.

drivers/tty/serial/serial_mctrl_gpio.c

···
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
- *
  */
 
 #include <linux/err.h>
 #include <linux/device.h>
+#include <linux/irq.h>
 #include <linux/gpio/consumer.h>
 #include <linux/termios.h>
+#include <linux/serial_core.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;
+	bool mctrl_on;
 };
 
 static const struct {
···
 }
 EXPORT_SYMBOL_GPL(mctrl_gpio_init_noauto);
 
+#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 & mctrl) & TIOCM_RI)
+			port->icount.rng++;
+
+		if ((mctrl_diff & mctrl) & 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;
+}
+
+struct mctrl_gpios *mctrl_gpio_init(struct uart_port *port, unsigned int idx)
+{
+	struct mctrl_gpios *gpios;
+	enum mctrl_gpio_idx i;
+
+	gpios = mctrl_gpio_init_noauto(port->dev, idx);
+	if (IS_ERR(gpios))
+		return gpios;
+
+	gpios->port = port;
+
+	for (i = 0; i < UART_GPIO_MAX; ++i) {
+		int ret;
+
+		if (!gpios->gpio[i] || mctrl_gpios_desc[i].dir_out)
+			continue;
+
+		ret = gpiod_to_irq(gpios->gpio[i]);
+		if (ret <= 0) {
+			dev_err(port->dev,
+				"failed to find corresponding irq for %s (idx=%d, err=%d)\n",
+				mctrl_gpios_desc[i].name, idx, ret);
+			return ERR_PTR(ret);
+		}
+		gpios->irq[i] = ret;
+
+		/* irqs should only be enabled in .enable_ms */
+		irq_set_status_flags(gpios->irq[i], IRQ_NOAUTOEN);
+
+		ret = devm_request_irq(port->dev, gpios->irq[i],
+				       mctrl_gpio_irq_handle,
+				       IRQ_TYPE_EDGE_BOTH, dev_name(port->dev),
+				       gpios);
+		if (ret) {
+			/* alternatively implement polling */
+			dev_err(port->dev,
+				"failed to request irq for %s (idx=%d, err=%d)\n",
+				mctrl_gpios_desc[i].name, idx, ret);
+			return ERR_PTR(ret);
+		}
+	}
+
+	return gpios;
+}
+
 void mctrl_gpio_free(struct device *dev, struct mctrl_gpios *gpios)
 {
 	enum mctrl_gpio_idx i;
 
-	for (i = 0; i < UART_GPIO_MAX; i++)
+	for (i = 0; i < UART_GPIO_MAX; i++) {
+		if (gpios->irq[i])
+			devm_free_irq(gpios->port->dev, gpios->irq[i], gpios);
+
 		if (gpios->gpio[i])
 			devm_gpiod_put(dev, gpios->gpio[i]);
+	}
 	devm_kfree(dev, gpios);
 }
 EXPORT_SYMBOL_GPL(mctrl_gpio_free);
+
+void mctrl_gpio_enable_ms(struct mctrl_gpios *gpios)
+{
+	enum mctrl_gpio_idx i;
+
+	/* .enable_ms may be called multiple times */
+	if (gpios->mctrl_on)
+		return;
+
+	gpios->mctrl_on = true;
+
+	/* 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])
+			continue;
+
+		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;
+
+	if (!gpios->mctrl_on)
+		return;
+
+	gpios->mctrl_on = false;
+
+	for (i = 0; i < UART_GPIO_MAX; ++i) {
+		if (!gpios->irq[i])
+			continue;
+
+		disable_irq(gpios->irq[i]);
+	}
+}

drivers/tty/serial/serial_mctrl_gpio.h

···
 #include <linux/device.h>
 #include <linux/gpio/consumer.h>
 
+struct uart_port;
+
 enum mctrl_gpio_idx {
 	UART_GPIO_CTS,
 	UART_GPIO_DSR,
···
 				      enum mctrl_gpio_idx gidx);
 
 /*
+ * Request and set direction of modem control lines GPIOs and sets up irq
+ * handling.
+ * 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 uart_port *port, unsigned int idx);
+
+/*
  * Request and set direction of modem control lines 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
···
  * be disposed of by the resource management code.
  */
 void mctrl_gpio_free(struct device *dev, struct mctrl_gpios *gpios);
+
+/*
+ * Enable gpio interrupts to report status line changes.
+ */
+void mctrl_gpio_enable_ms(struct mctrl_gpios *gpios);
+
+/*
+ * Disable gpio interrupts to report status line changes.
+ */
+void mctrl_gpio_disable_ms(struct mctrl_gpios *gpios);
 
 #else /* GPIOLIB */
 
···
 }
 
 static inline
+struct mctrl_gpios *mctrl_gpio_init(struct uart_port *port, unsigned int idx)
+{
+	return ERR_PTR(-ENOSYS);
+}
+
+static inline
 struct mctrl_gpios *mctrl_gpio_init_noauto(struct device *dev, unsigned int idx)
 {
 	return ERR_PTR(-ENOSYS);
···
 
 static inline
 void mctrl_gpio_free(struct device *dev, struct mctrl_gpios *gpios)
+{
+}
+
+void mctrl_gpio_enable_ms(struct mctrl_gpios *gpios)
+{
+}
+
+void mctrl_gpio_disable_ms(struct mctrl_gpios *gpios)
 {
 }