pinctrl: ocelot: add support for interrupt controller

This GPIO controller can serve as an interrupt controller as well on the
GPIOs it handles.

An interrupt is generated whenever a GPIO line changes and the
interrupt for this GPIO line is enabled. This means that both the
changes from low to high and high to low generate an interrupt.

For some use cases, it makes sense to ignore the high to low change and
not generate an interrupt. Such a use case is a line that is hold in a
level high/low manner until the event holding the line gets acked.
This can be achieved by making sure the interrupt on the GPIO controller
side gets acked and masked only after the line gets hold in its default
state, this is what's done with the fasteoi functions.

Only IRQ_TYPE_EDGE_BOTH and IRQ_TYPE_LEVEL_HIGH are supported for now.

Signed-off-by: Quentin Schulz <quentin.schulz@bootlin.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/pinctrl/Kconfig

@@ -332,6 +332,7 @@ config PINCTRL_OCELOT
 	depends on OF
 	depends on MSCC_OCELOT || COMPILE_TEST
 	select GPIOLIB
+	select GPIOLIB_IRQCHIP
 	select GENERIC_PINCONF
 	select GENERIC_PINCTRL_GROUPS
 	select GENERIC_PINMUX_FUNCTIONS

drivers/pinctrl/pinctrl-ocelot.c

@@ -11,6 +11,7 @@
 #include <linux/interrupt.h>
 #include <linux/io.h>
 #include <linux/of_device.h>
+#include <linux/of_irq.h>
 #include <linux/of_platform.h>
 #include <linux/pinctrl/pinctrl.h>
 #include <linux/pinctrl/pinmux.h>
@@ -427,11 +428,98 @@ static const struct gpio_chip ocelot_gpiolib_chip = {
 	.owner = THIS_MODULE,
 };
 
+static void ocelot_irq_mask(struct irq_data *data)
+{
+	struct gpio_chip *chip = irq_data_get_irq_chip_data(data);
+	struct ocelot_pinctrl *info = gpiochip_get_data(chip);
+	unsigned int gpio = irqd_to_hwirq(data);
+
+	regmap_update_bits(info->map, OCELOT_GPIO_INTR_ENA, BIT(gpio), 0);
+}
+
+static void ocelot_irq_unmask(struct irq_data *data)
+{
+	struct gpio_chip *chip = irq_data_get_irq_chip_data(data);
+	struct ocelot_pinctrl *info = gpiochip_get_data(chip);
+	unsigned int gpio = irqd_to_hwirq(data);
+
+	regmap_update_bits(info->map, OCELOT_GPIO_INTR_ENA, BIT(gpio),
+			   BIT(gpio));
+}
+
+static void ocelot_irq_ack(struct irq_data *data)
+{
+	struct gpio_chip *chip = irq_data_get_irq_chip_data(data);
+	struct ocelot_pinctrl *info = gpiochip_get_data(chip);
+	unsigned int gpio = irqd_to_hwirq(data);
+
+	regmap_write_bits(info->map, OCELOT_GPIO_INTR, BIT(gpio), BIT(gpio));
+}
+
+static int ocelot_irq_set_type(struct irq_data *data, unsigned int type);
+
+static struct irq_chip ocelot_eoi_irqchip = {
+	.name		= "gpio",
+	.irq_mask	= ocelot_irq_mask,
+	.irq_eoi	= ocelot_irq_ack,
+	.irq_unmask	= ocelot_irq_unmask,
+	.flags          = IRQCHIP_EOI_THREADED | IRQCHIP_EOI_IF_HANDLED,
+	.irq_set_type	= ocelot_irq_set_type,
+};
+
+static struct irq_chip ocelot_irqchip = {
+	.name		= "gpio",
+	.irq_mask	= ocelot_irq_mask,
+	.irq_ack	= ocelot_irq_ack,
+	.irq_unmask	= ocelot_irq_unmask,
+	.irq_set_type	= ocelot_irq_set_type,
+};
+
+static int ocelot_irq_set_type(struct irq_data *data, unsigned int type)
+{
+	type &= IRQ_TYPE_SENSE_MASK;
+
+	if (!(type & (IRQ_TYPE_EDGE_BOTH | IRQ_TYPE_LEVEL_HIGH)))
+		return -EINVAL;
+
+	if (type & IRQ_TYPE_LEVEL_HIGH)
+		irq_set_chip_handler_name_locked(data, &ocelot_eoi_irqchip,
+						 handle_fasteoi_irq, NULL);
+	if (type & IRQ_TYPE_EDGE_BOTH)
+		irq_set_chip_handler_name_locked(data, &ocelot_irqchip,
+						 handle_edge_irq, NULL);
+
+	return 0;
+}
+
+static void ocelot_irq_handler(struct irq_desc *desc)
+{
+	struct irq_chip *parent_chip = irq_desc_get_chip(desc);
+	struct gpio_chip *chip = irq_desc_get_handler_data(desc);
+	struct ocelot_pinctrl *info = gpiochip_get_data(chip);
+	unsigned int reg = 0, irq;
+	unsigned long irqs;
+
+	regmap_read(info->map, OCELOT_GPIO_INTR_IDENT, &reg);
+	if (!reg)
+		return;
+
+	chained_irq_enter(parent_chip, desc);
+
+	irqs = reg;
+
+	for_each_set_bit(irq, &irqs, OCELOT_PINS) {
+		generic_handle_irq(irq_linear_revmap(chip->irq.domain, irq));
+	}
+
+	chained_irq_exit(parent_chip, desc);
+}
+
 static int ocelot_gpiochip_register(struct platform_device *pdev,
 				    struct ocelot_pinctrl *info)
 {
 	struct gpio_chip *gc;
-	int ret;
+	int ret, irq;
 
 	info->gpio_chip = ocelot_gpiolib_chip;
 
@@ -446,7 +534,17 @@ static int ocelot_gpiochip_register(struct platform_device *pdev,
 	if (ret)
 		return ret;
 
-	/* TODO: this can be used as an irqchip but no board is using that */
+	irq = irq_of_parse_and_map(pdev->dev.of_node, 0);
+	if (irq <= 0)
+		return irq;
+
+	ret = gpiochip_irqchip_add(gc, &ocelot_irqchip, 0, handle_edge_irq,
+				   IRQ_TYPE_NONE);
+	if (ret)
+		return ret;
+
+	gpiochip_set_chained_irqchip(gc, &ocelot_irqchip, irq,
+				     ocelot_irq_handler);
 
 	return 0;
 }