gpio: pcf857x: handle only enabled irqs

Now pcf857x_irq() IRQ's dispatcher will try to run nested
IRQ handlers for each GPIO pin which state has changed.
Such IRQs are, actually, spurious and nested IRQ handlers
have to be called only for IRQs wich were enabled by users.
This is not critical issue - just /proc/interrupts
will display counters for unused IRQS:
399: 4 0 pcf857x 0 Edge
428: 1 0 pcf857x 13 Edge
430: 1 0 pcf857x 15 Edge

Hence, fix it by adding irq_enabled field in struct pcf857x to track
enabled GPIO IRQs and corresponding callbacks in pcf857x_irq_chip.

Similar functionality was presented in pcf857x driver, commit
21fd3cd1874a ('gpio: pcf857x: call the gpio user handler iff...')

and then it was removed by commit
a39294bdf4b0 ('gpio: pcf857x: Switch to use gpiolib irqchip...')

Cc: Geert Uytterhoeven <[e-mail]>
Fixes: a39294bdf4b0 ('gpio: pcf857x: Switch to use gpiolib irqchip helpers')
Signed-off-by: Grygorii Strashko <[e-mail]>
Signed-off-by: Linus Walleij <[e-mail]>

drivers/gpio/gpio-pcf857x.c

···
 	unsigned		out;		/* software latch */
 	unsigned		status;		/* current status */
 	unsigned int		irq_parent;
+	unsigned		irq_enabled;	/* enabled irqs */
 
 	int (*write)(struct i2c_client *client, unsigned data);
 	int (*read)(struct i2c_client *client);
···
 	 * interrupt source, just to avoid bad irqs
 	 */
 
-	change = (gpio->status ^ status);
+	change = (gpio->status ^ status) & gpio->irq_enabled;
 	for_each_set_bit(i, &change, gpio->chip.ngpio)
 		handle_nested_irq(irq_find_mapping(gpio->chip.irqdomain, i));
 	gpio->status = status;
···
  */
 static void noop(struct irq_data *data) { }
 
-static unsigned int noop_ret(struct irq_data *data)
-{
-	return 0;
-}
-
 static int pcf857x_irq_set_wake(struct irq_data *data, unsigned int on)
 {
 	struct pcf857x *gpio = irq_data_get_irq_chip_data(data);
+
 	int error = 0;
 
 	if (gpio->irq_parent) {
···
 			gpio->irq_parent = 0;
 		}
 	}
-
 	return error;
+}
+
+static void pcf857x_irq_enable(struct irq_data *data)
+{
+	struct pcf857x *gpio = irq_data_get_irq_chip_data(data);
+
+	gpio->irq_enabled |= (1 << data->hwirq);
+}
+
+static void pcf857x_irq_disable(struct irq_data *data)
+{
+	struct pcf857x *gpio = irq_data_get_irq_chip_data(data);
+
+	gpio->irq_enabled &= ~(1 << data->hwirq);
+}
+
+static void pcf857x_irq_bus_lock(struct irq_data *data)
+{
+	struct pcf857x *gpio = irq_data_get_irq_chip_data(data);
+
+	mutex_lock(&gpio->lock);
+}
+
+static void pcf857x_irq_bus_sync_unlock(struct irq_data *data)
+{
+	struct pcf857x *gpio = irq_data_get_irq_chip_data(data);
+
+	mutex_unlock(&gpio->lock);
 }
 
 static struct irq_chip pcf857x_irq_chip = {
 	.name		= "pcf857x",
-	.irq_startup	= noop_ret,
-	.irq_shutdown	= noop,
-	.irq_enable	= noop,
-	.irq_disable	= noop,
+	.irq_enable	= pcf857x_irq_enable,
+	.irq_disable	= pcf857x_irq_disable,
 	.irq_ack	= noop,
 	.irq_mask	= noop,
 	.irq_unmask	= noop,
 	.irq_set_wake	= pcf857x_irq_set_wake,
+	.irq_bus_lock		= pcf857x_irq_bus_lock,
+	.irq_bus_sync_unlock	= pcf857x_irq_bus_sync_unlock,
 };
 
 /*-------------------------------------------------------------------------*/