gpio: pcf857x: enable gpio_to_irq() support

pcf857x chip has some pins, but interrupt pin is only 1 pin.
And gpiolib requests 1 interrupt per 1 gpio pin.

Thus, this patch added demuxed irq to pcf857x driver,
and enabled gpio_to_irq().

Signed-off-by: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-pcf857x.c

@@ -23,7 +23,12 @@
 #include <linux/gpio.h>
 #include <linux/i2c.h>
 #include <linux/i2c/pcf857x.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/irqdomain.h>
 #include <linux/module.h>
+#include <linux/spinlock.h>
+#include <linux/workqueue.h>
 
 
 static const struct i2c_device_id pcf857x_id[] = {
@@ -60,7 +65,12 @@ struct pcf857x {
 	struct gpio_chip	chip;
 	struct i2c_client	*client;
 	struct mutex		lock;		/* protect 'out' */
+	struct work_struct	work;		/* irq demux work */
+	struct irq_domain	*irq_domain;	/* for irq demux  */
+	spinlock_t		slock;		/* protect irq demux */
 	unsigned		out;		/* software latch */
+	unsigned		status;		/* current status */
+	int			irq;		/* real irq number */
 
 	int (*write)(struct i2c_client *client, unsigned data);
 	int (*read)(struct i2c_client *client);
@@ -150,6 +160,100 @@ static void pcf857x_set(struct gpio_chip *chip, unsigned offset, int value)
 
 /*-------------------------------------------------------------------------*/
 
+static int pcf857x_to_irq(struct gpio_chip *chip, unsigned offset)
+{
+	struct pcf857x *gpio = container_of(chip, struct pcf857x, chip);
+
+	return irq_create_mapping(gpio->irq_domain, offset);
+}
+
+static void pcf857x_irq_demux_work(struct work_struct *work)
+{
+	struct pcf857x *gpio = container_of(work,
+					       struct pcf857x,
+					       work);
+	unsigned long change, i, status, flags;
+
+	status = gpio->read(gpio->client);
+
+	spin_lock_irqsave(&gpio->slock, flags);
+
+	change = gpio->status ^ status;
+	for_each_set_bit(i, &change, gpio->chip.ngpio)
+		generic_handle_irq(irq_find_mapping(gpio->irq_domain, i));
+	gpio->status = status;
+
+	spin_unlock_irqrestore(&gpio->slock, flags);
+}
+
+static irqreturn_t pcf857x_irq_demux(int irq, void *data)
+{
+	struct pcf857x	*gpio = data;
+
+	/*
+	 * pcf857x can't read/write data here,
+	 * since i2c data access might go to sleep.
+	 */
+	schedule_work(&gpio->work);
+
+	return IRQ_HANDLED;
+}
+
+static int pcf857x_irq_domain_map(struct irq_domain *domain, unsigned int virq,
+				 irq_hw_number_t hw)
+{
+	irq_set_chip_and_handler(virq,
+				 &dummy_irq_chip,
+				 handle_level_irq);
+	return 0;
+}
+
+static struct irq_domain_ops pcf857x_irq_domain_ops = {
+	.map	= pcf857x_irq_domain_map,
+};
+
+static void pcf857x_irq_domain_cleanup(struct pcf857x *gpio)
+{
+	if (gpio->irq_domain)
+		irq_domain_remove(gpio->irq_domain);
+
+	if (gpio->irq)
+		free_irq(gpio->irq, gpio);
+}
+
+static int pcf857x_irq_domain_init(struct pcf857x *gpio,
+				   struct pcf857x_platform_data *pdata,
+				   struct device *dev)
+{
+	int status;
+
+	gpio->irq_domain = irq_domain_add_linear(dev->of_node,
+						 gpio->chip.ngpio,
+						 &pcf857x_irq_domain_ops,
+						 NULL);
+	if (!gpio->irq_domain)
+		goto fail;
+
+	/* enable real irq */
+	status = request_irq(pdata->irq, pcf857x_irq_demux, 0,
+			     dev_name(dev), gpio);
+	if (status)
+		goto fail;
+
+	/* enable gpio_to_irq() */
+	INIT_WORK(&gpio->work, pcf857x_irq_demux_work);
+	gpio->chip.to_irq	= pcf857x_to_irq;
+	gpio->irq		= pdata->irq;
+
+	return 0;
+
+fail:
+	pcf857x_irq_domain_cleanup(gpio);
+	return -EINVAL;
+}
+
+/*-------------------------------------------------------------------------*/
+
 static int pcf857x_probe(struct i2c_client *client,
 			 const struct i2c_device_id *id)
 {
@@ -168,6 +272,7 @@ static int pcf857x_probe(struct i2c_client *client,
 		return -ENOMEM;
 
 	mutex_init(&gpio->lock);
+	spin_lock_init(&gpio->slock);
 
 	gpio->chip.base			= pdata ? pdata->gpio_base : -1;
 	gpio->chip.can_sleep		= 1;
@@ -179,6 +284,15 @@ static int pcf857x_probe(struct i2c_client *client,
 	gpio->chip.direction_output	= pcf857x_output;
 	gpio->chip.ngpio		= id->driver_data;
 
+	/* enable gpio_to_irq() if platform has settings */
+	if (pdata->irq) {
+		status = pcf857x_irq_domain_init(gpio, pdata, &client->dev);
+		if (status < 0) {
+			dev_err(&client->dev, "irq_domain init failed\n");
+			goto fail;
+		}
+	}
+
 	/* NOTE:  the OnSemi jlc1562b is also largely compatible with
 	 * these parts, notably for output.  It has a low-resolution
 	 * DAC instead of pin change IRQs; and its inputs can be the
@@ -248,6 +362,7 @@ static int pcf857x_probe(struct i2c_client *client,
 	 * all-ones reset state.  Otherwise it flags pins to be driven low.
 	 */
 	gpio->out = pdata ? ~pdata->n_latch : ~0;
+	gpio->status = gpio->out;
 
 	status = gpiochip_add(&gpio->chip);
 	if (status < 0)
@@ -278,6 +393,10 @@ static int pcf857x_probe(struct i2c_client *client,
 fail:
 	dev_dbg(&client->dev, "probe error %d for '%s'\n",
 			status, client->name);
+
+	if (pdata->irq)
+		pcf857x_irq_domain_cleanup(gpio);
+
 	kfree(gpio);
 	return status;
 }
@@ -299,6 +418,9 @@ static int pcf857x_remove(struct i2c_client *client)
 		}
 	}
 
+	if (pdata->irq)
+		pcf857x_irq_domain_cleanup(gpio);
+
 	status = gpiochip_remove(&gpio->chip);
 	if (status == 0)
 		kfree(gpio);

include/linux/i2c/pcf857x.h

@@ -10,6 +10,7 @@
  * @setup: optional callback issued once the GPIOs are valid
  * @teardown: optional callback issued before the GPIOs are invalidated
  * @context: optional parameter passed to setup() and teardown()
+ * @irq: optional interrupt number
  *
  * In addition to the I2C_BOARD_INFO() state appropriate to each chip,
  * the i2c_board_info used with the pcf875x driver must provide its
@@ -39,6 +40,8 @@ struct pcf857x_platform_data {
 					int gpio, unsigned ngpio,
 					void *context);
 	void		*context;
+
+	int		irq;
 };
 
 #endif /* __LINUX_PCF857X_H */