gpio: add IRQ chip helpers in gpiolib

This provides a function gpiochip_irqchip_add() to set
up an irqchip for a GPIO controller, and a function
gpiochip_set_chained_irqchip() to chain it to a parent
irqchip.

Most GPIOs are of the type where a number of lines form
a cascaded interrupt controller chained onto
the primary system interrupt controller (or further down the
chain) so let's add this helper and factor the code to
request the lines to be used as IRQs, the .to_irq() function
and the irqdomain into the core as well.

Acked-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/Kconfig

@@ -55,6 +55,9 @@ config GPIO_ACPI
 	def_bool y
 	depends on ACPI
 
+config GPIOLIB_IRQCHIP
+	bool
+
 config DEBUG_GPIO
 	bool "Debug GPIO calls"
 	depends on DEBUG_KERNEL

drivers/gpio/gpiolib.c

@@ -1254,6 +1254,9 @@ fail:
 }
 EXPORT_SYMBOL_GPL(gpiochip_add);
 
+/* Forward-declaration */
+static void gpiochip_irqchip_remove(struct gpio_chip *gpiochip);
+
 /**
  * gpiochip_remove() - unregister a gpio_chip
  * @chip: the chip to unregister
@@ -1270,6 +1273,7 @@ int gpiochip_remove(struct gpio_chip *chip)
 
 	spin_lock_irqsave(&gpio_lock, flags);
 
+	gpiochip_irqchip_remove(chip);
 	gpiochip_remove_pin_ranges(chip);
 	of_gpiochip_remove(chip);
 
@@ -1339,6 +1343,190 @@ static struct gpio_chip *find_chip_by_name(const char *name)
 	return gpiochip_find((void *)name, gpiochip_match_name);
 }
 
+#ifdef CONFIG_GPIOLIB_IRQCHIP
+
+/*
+ * The following is irqchip helper code for gpiochips.
+ */
+
+/**
+ * gpiochip_add_chained_irqchip() - adds a chained irqchip to a gpiochip
+ * @gpiochip: the gpiochip to add the irqchip to
+ * @irqchip: the irqchip to add to the gpiochip
+ * @parent_irq: the irq number corresponding to the parent IRQ for this
+ * chained irqchip
+ * @parent_handler: the parent interrupt handler for the accumulated IRQ
+ * coming out of the gpiochip
+ */
+void gpiochip_set_chained_irqchip(struct gpio_chip *gpiochip,
+				  struct irq_chip *irqchip,
+				  int parent_irq,
+				  irq_flow_handler_t parent_handler)
+{
+	irq_set_chained_handler(parent_irq, parent_handler);
+	/*
+	 * The parent irqchip is already using the chip_data for this
+	 * irqchip, so our callbacks simply use the handler_data.
+	 */
+	irq_set_handler_data(parent_irq, gpiochip);
+}
+EXPORT_SYMBOL_GPL(gpiochip_set_chained_irqchip);
+
+/**
+ * gpiochip_irq_map() - maps an IRQ into a GPIO irqchip
+ * @d: the irqdomain used by this irqchip
+ * @irq: the global irq number used by this GPIO irqchip irq
+ * @hwirq: the local IRQ/GPIO line offset on this gpiochip
+ *
+ * This function will set up the mapping for a certain IRQ line on a
+ * gpiochip by assigning the gpiochip as chip data, and using the irqchip
+ * stored inside the gpiochip.
+ */
+static int gpiochip_irq_map(struct irq_domain *d, unsigned int irq,
+			    irq_hw_number_t hwirq)
+{
+	struct gpio_chip *chip = d->host_data;
+
+	irq_set_chip_and_handler(irq, chip->irqchip, chip->irq_handler);
+	irq_set_chip_data(irq, chip);
+#ifdef CONFIG_ARM
+	set_irq_flags(irq, IRQF_VALID);
+#else
+	irq_set_noprobe(irq);
+#endif
+	irq_set_irq_type(irq, chip->irq_default_type);
+
+	return 0;
+}
+
+static const struct irq_domain_ops gpiochip_domain_ops = {
+	.map	= gpiochip_irq_map,
+	/* Virtually all GPIO irqchips are twocell:ed */
+	.xlate	= irq_domain_xlate_twocell,
+};
+
+static int gpiochip_irq_reqres(struct irq_data *d)
+{
+	struct gpio_chip *chip = irq_data_get_irq_chip_data(d);
+
+	if (gpio_lock_as_irq(chip, d->hwirq)) {
+		chip_err(chip,
+			"unable to lock HW IRQ %lu for IRQ\n",
+			d->hwirq);
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static void gpiochip_irq_relres(struct irq_data *d)
+{
+	struct gpio_chip *chip = irq_data_get_irq_chip_data(d);
+
+	gpio_unlock_as_irq(chip, d->hwirq);
+}
+
+static int gpiochip_to_irq(struct gpio_chip *chip, unsigned offset)
+{
+	return irq_find_mapping(chip->irqdomain, offset);
+}
+
+/**
+ * gpiochip_irqchip_remove() - removes an irqchip added to a gpiochip
+ * @gpiochip: the gpiochip to remove the irqchip from
+ *
+ * This is called only from gpiochip_remove()
+ */
+static void gpiochip_irqchip_remove(struct gpio_chip *gpiochip)
+{
+	if (gpiochip->irqdomain)
+		irq_domain_remove(gpiochip->irqdomain);
+
+	if (gpiochip->irqchip) {
+		gpiochip->irqchip->irq_request_resources = NULL;
+		gpiochip->irqchip->irq_release_resources = NULL;
+		gpiochip->irqchip = NULL;
+	}
+}
+
+/**
+ * gpiochip_irqchip_add() - adds an irqchip to a gpiochip
+ * @gpiochip: the gpiochip to add the irqchip to
+ * @irqchip: the irqchip to add to the gpiochip
+ * @first_irq: if not dynamically assigned, the base (first) IRQ to
+ * allocate gpiochip irqs from
+ * @handler: the irq handler to use (often a predefined irq core function)
+ * @type: the default type for IRQs on this irqchip
+ *
+ * This function closely associates a certain irqchip with a certain
+ * gpiochip, providing an irq domain to translate the local IRQs to
+ * global irqs in the gpiolib core, and making sure that the gpiochip
+ * is passed as chip data to all related functions. Driver callbacks
+ * need to use container_of() to get their local state containers back
+ * from the gpiochip passed as chip data. An irqdomain will be stored
+ * in the gpiochip that shall be used by the driver to handle IRQ number
+ * translation. The gpiochip will need to be initialized and registered
+ * before calling this function.
+ *
+ * This function will handle two cell:ed simple IRQs. Everything else
+ * need to be open coded.
+ */
+int gpiochip_irqchip_add(struct gpio_chip *gpiochip,
+			 struct irq_chip *irqchip,
+			 unsigned int first_irq,
+			 irq_flow_handler_t handler,
+			 unsigned int type)
+{
+	struct device_node *of_node;
+	unsigned int offset;
+
+	if (!gpiochip || !irqchip)
+		return -EINVAL;
+
+	if (!gpiochip->dev) {
+		pr_err("missing gpiochip .dev parent pointer\n");
+		return -EINVAL;
+	}
+	of_node = gpiochip->dev->of_node;
+#ifdef CONFIG_OF_GPIO
+	/*
+	 * If the gpiochip has an assigned OF node this takes precendence
+	 * FIXME: get rid of this and use gpiochip->dev->of_node everywhere
+	 */
+	if (gpiochip->of_node)
+		of_node = gpiochip->of_node;
+#endif
+	gpiochip->irqchip = irqchip;
+	gpiochip->irq_handler = handler;
+	gpiochip->irq_default_type = type;
+	gpiochip->to_irq = gpiochip_to_irq;
+	gpiochip->irqdomain = irq_domain_add_simple(of_node,
+					gpiochip->ngpio, first_irq,
+					&gpiochip_domain_ops, gpiochip);
+	if (!gpiochip->irqdomain) {
+		gpiochip->irqchip = NULL;
+		return -EINVAL;
+	}
+	irqchip->irq_request_resources = gpiochip_irq_reqres;
+	irqchip->irq_release_resources = gpiochip_irq_relres;
+
+	/*
+	 * Prepare the mapping since the irqchip shall be orthogonal to
+	 * any gpiochip calls. If the first_irq was zero, this is
+	 * necessary to allocate descriptors for all IRQs.
+	 */
+	for (offset = 0; offset < gpiochip->ngpio; offset++)
+		irq_create_mapping(gpiochip->irqdomain, offset);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(gpiochip_irqchip_add);
+
+#else /* CONFIG_GPIOLIB_IRQCHIP */
+
+static void gpiochip_irqchip_remove(struct gpio_chip *gpiochip) {}
+
+#endif /* CONFIG_GPIOLIB_IRQCHIP */
+
 #ifdef CONFIG_PINCTRL
 
 /**

include/linux/gpio/driver.h

@@ -3,6 +3,9 @@
 
 #include <linux/types.h>
 #include <linux/module.h>
+#include <linux/irq.h>
+#include <linux/irqchip/chained_irq.h>
+#include <linux/irqdomain.h>
 
 struct device;
 struct gpio_desc;
@@ -97,6 +100,17 @@ struct gpio_chip {
 	bool			can_sleep;
 	bool			exported;
 
+#ifdef CONFIG_GPIOLIB_IRQCHIP
+	/*
+	 * With CONFIG_GPIO_IRQCHIP we get an irqchip inside the gpiolib
+	 * to handle IRQs for most practical cases.
+	 */
+	struct irq_chip		*irqchip;
+	struct irq_domain	*irqdomain;
+	irq_flow_handler_t	irq_handler;
+	unsigned int		irq_default_type;
+#endif
+
 #if defined(CONFIG_OF_GPIO)
 	/*
 	 * If CONFIG_OF is enabled, then all GPIO controllers described in the
@@ -190,6 +204,21 @@ struct gpiod_lookup_table {
 
 void gpiod_add_lookup_table(struct gpiod_lookup_table *table);
 
+#ifdef CONFIG_GPIOLIB_IRQCHIP
+
+void gpiochip_set_chained_irqchip(struct gpio_chip *gpiochip,
+		struct irq_chip *irqchip,
+		int parent_irq,
+		irq_flow_handler_t parent_handler);
+
+int gpiochip_irqchip_add(struct gpio_chip *gpiochip,
+		struct irq_chip *irqchip,
+		unsigned int first_irq,
+		irq_flow_handler_t handler,
+		unsigned int type);
+
+#endif /* CONFIG_GPIO_IRQCHIP */
+
 #else /* CONFIG_GPIOLIB */
 
 static inline struct gpio_chip *gpiod_to_chip(const struct gpio_desc *desc)