irq: add irq_domain translation infrastructure

This patch adds irq_domain infrastructure for translating from
hardware irq numbers to linux irqs.  This is particularly important
for architectures adding device tree support because the current
implementation (excluding PowerPC and SPARC) cannot handle
translation for more than a single interrupt controller.  irq_domain
supports device tree translation for any number of interrupt
controllers.

This patch converts x86, Microblaze, ARM and MIPS to use irq_domain
for device tree irq translation.  x86 is untested beyond compiling it,
irq_domain is enabled for MIPS and Microblaze, but the old behaviour is
preserved until the core code is modified to actually register an
irq_domain yet.  On ARM it works and is required for much of the new
ARM device tree board support.

PowerPC has /not/ been converted to use this new infrastructure.  It
is still missing some features before it can replace the virq
infrastructure already in powerpc (see documentation on
irq_domain_map/unmap for details).  Followup patches will add the
missing pieces and migrate PowerPC to use irq_domain.

SPARC has its own method of managing interrupts from the device tree
and is unaffected by this change.
Acked-by: Ralf Baechle <ralf@linux-mips.org>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>

arch/arm/Kconfig

@@ -1682,6 +1682,7 @@ config USE_OF
 	bool "Flattened Device Tree support"
 	select OF
 	select OF_EARLY_FLATTREE
+	select IRQ_DOMAIN
 	help
 	  Include support for flattened device tree machine descriptions.
 

arch/arm/include/asm/prom.h

@@ -16,11 +16,6 @@
 #include <asm/setup.h>
 #include <asm/irq.h>
 
-static inline void irq_dispose_mapping(unsigned int virq)
-{
-	return;
-}
-
 extern struct machine_desc *setup_machine_fdt(unsigned int dt_phys);
 extern void arm_dt_memblock_reserve(void);
 

arch/arm/kernel/devtree.c

@@ -132,17 +132,3 @@ struct machine_desc * __init setup_machine_fdt(unsigned int dt_phys)
 
 	return mdesc_best;
 }
-
-/**
- * irq_create_of_mapping - Hook to resolve OF irq specifier into a Linux irq#
- *
- * Currently the mapping mechanism is trivial; simple flat hwirq numbers are
- * mapped 1:1 onto Linux irq numbers.  Cascaded irq controllers are not
- * supported.
- */
-unsigned int irq_create_of_mapping(struct device_node *controller,
-				   const u32 *intspec, unsigned int intsize)
-{
-	return intspec[0];
-}
-EXPORT_SYMBOL_GPL(irq_create_of_mapping);

include/linux/irq.h

@@ -108,14 +108,18 @@ enum {
 };
 
 struct msi_desc;
+struct irq_domain;
 
 /**
  * struct irq_data - per irq and irq chip data passed down to chip functions
  * @irq:		interrupt number
+ * @hwirq:		hardware interrupt number, local to the interrupt domain
  * @node:		node index useful for balancing
  * @state_use_accessors: status information for irq chip functions.
  *			Use accessor functions to deal with it
  * @chip:		low level interrupt hardware access
+ * @domain:		Interrupt translation domain; responsible for mapping
+ *			between hwirq number and linux irq number.
  * @handler_data:	per-IRQ data for the irq_chip methods
  * @chip_data:		platform-specific per-chip private data for the chip
  *			methods, to allow shared chip implementations
@@ -128,9 +132,11 @@ struct msi_desc;
  */
 struct irq_data {
 	unsigned int		irq;
+	unsigned long		hwirq;
 	unsigned int		node;
 	unsigned int		state_use_accessors;
 	struct irq_chip		*chip;
+	struct irq_domain	*domain;
 	void			*handler_data;
 	void			*chip_data;
 	struct msi_desc		*msi_desc;

include/linux/irqdomain.h

+/*
+ * irq_domain - IRQ translation domains
+ *
+ * Translation infrastructure between hw and linux irq numbers.  This is
+ * helpful for interrupt controllers to implement mapping between hardware
+ * irq numbers and the Linux irq number space.
+ *
+ * irq_domains also have a hook for translating device tree interrupt
+ * representation into a hardware irq number that can be mapped back to a
+ * Linux irq number without any extra platform support code.
+ *
+ * irq_domain is expected to be embedded in an interrupt controller's private
+ * data structure.
+ */
+#ifndef _LINUX_IRQDOMAIN_H
+#define _LINUX_IRQDOMAIN_H
+
+#include <linux/irq.h>
+
+#ifdef CONFIG_IRQ_DOMAIN
+struct device_node;
+struct irq_domain;
+
+/**
+ * struct irq_domain_ops - Methods for irq_domain objects
+ * @to_irq: (optional) given a local hardware irq number, return the linux
+ *          irq number.  If to_irq is not implemented, then the irq_domain
+ *          will use this translation: irq = (domain->irq_base + hwirq)
+ * @dt_translate: Given a device tree node and interrupt specifier, decode
+ *                the hardware irq number and linux irq type value.
+ */
+struct irq_domain_ops {
+	unsigned int (*to_irq)(struct irq_domain *d, unsigned long hwirq);
+
+#ifdef CONFIG_OF
+	int (*dt_translate)(struct irq_domain *d, struct device_node *node,
+			    const u32 *intspec, unsigned int intsize,
+			    unsigned long *out_hwirq, unsigned int *out_type);
+#endif /* CONFIG_OF */
+};
+
+/**
+ * struct irq_domain - Hardware interrupt number translation object
+ * @list: Element in global irq_domain list.
+ * @irq_base: Start of irq_desc range assigned to the irq_domain.  The creator
+ *            of the irq_domain is responsible for allocating the array of
+ *            irq_desc structures.
+ * @nr_irq: Number of irqs managed by the irq domain
+ * @ops: pointer to irq_domain methods
+ * @priv: private data pointer for use by owner.  Not touched by irq_domain
+ *        core code.
+ * @of_node: (optional) Pointer to device tree nodes associated with the
+ *           irq_domain.  Used when decoding device tree interrupt specifiers.
+ */
+struct irq_domain {
+	struct list_head list;
+	unsigned int irq_base;
+	unsigned int nr_irq;
+	const struct irq_domain_ops *ops;
+	void *priv;
+	struct device_node *of_node;
+};
+
+/**
+ * irq_domain_to_irq() - Translate from a hardware irq to a linux irq number
+ *
+ * Returns the linux irq number associated with a hardware irq.  By default,
+ * the mapping is irq == domain->irq_base + hwirq, but this mapping can
+ * be overridden if the irq_domain implements a .to_irq() hook.
+ */
+static inline unsigned int irq_domain_to_irq(struct irq_domain *d,
+					     unsigned long hwirq)
+{
+	return d->ops->to_irq ? d->ops->to_irq(d, hwirq) : d->irq_base + hwirq;
+}
+
+extern void irq_domain_add(struct irq_domain *domain);
+extern void irq_domain_del(struct irq_domain *domain);
+#endif /* CONFIG_IRQ_DOMAIN */
+
+#endif /* _LINUX_IRQDOMAIN_H */

include/linux/of_irq.h

@@ -63,6 +63,9 @@ extern int of_irq_map_one(struct device_node *device, int index,
 extern unsigned int irq_create_of_mapping(struct device_node *controller,
 					  const u32 *intspec,
 					  unsigned int intsize);
+#ifdef CONFIG_IRQ_DOMAIN
+extern void irq_dispose_mapping(unsigned int irq);
+#endif
 extern int of_irq_to_resource(struct device_node *dev, int index,
 			      struct resource *r);
 extern int of_irq_count(struct device_node *dev);
@@ -70,6 +73,7 @@ extern int of_irq_to_resource_table(struct device_node *dev,
 		struct resource *res, int nr_irqs);
 extern struct device_node *of_irq_find_parent(struct device_node *child);
 
+
 #endif /* CONFIG_OF_IRQ */
 #endif /* CONFIG_OF */
 #endif /* __OF_IRQ_H */

kernel/irq/Kconfig

@@ -52,6 +52,10 @@ config IRQ_EDGE_EOI_HANDLER
 config GENERIC_IRQ_CHIP
        bool
 
+# Generic irq_domain hw <--> linux irq number translation
+config IRQ_DOMAIN
+	bool
+
 # Support forced irq threading
 config IRQ_FORCED_THREADING
        bool

kernel/irq/Makefile

@@ -2,6 +2,7 @@
 obj-y := irqdesc.o handle.o manage.o spurious.o resend.o chip.o dummychip.o devres.o
 obj-$(CONFIG_GENERIC_IRQ_CHIP) += generic-chip.o
 obj-$(CONFIG_GENERIC_IRQ_PROBE) += autoprobe.o
+obj-$(CONFIG_IRQ_DOMAIN) += irqdomain.o
 obj-$(CONFIG_PROC_FS) += proc.o
 obj-$(CONFIG_GENERIC_PENDING_IRQ) += migration.o
 obj-$(CONFIG_PM_SLEEP) += pm.o

kernel/irq/irqdomain.c

+#include <linux/irq.h>
+#include <linux/irqdomain.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+
+static LIST_HEAD(irq_domain_list);
+static DEFINE_MUTEX(irq_domain_mutex);
+
+/**
+ * irq_domain_add() - Register an irq_domain
+ * @domain: ptr to initialized irq_domain structure
+ *
+ * Registers an irq_domain structure.  The irq_domain must at a minimum be
+ * initialized with an ops structure pointer, and either a ->to_irq hook or
+ * a valid irq_base value.  Everything else is optional.
+ */
+void irq_domain_add(struct irq_domain *domain)
+{
+	struct irq_data *d;
+	int hwirq;
+
+	/*
+	 * This assumes that the irq_domain owner has already allocated
+	 * the irq_descs.  This block will be removed when support for dynamic
+	 * allocation of irq_descs is added to irq_domain.
+	 */
+	for (hwirq = 0; hwirq < domain->nr_irq; hwirq++) {
+		d = irq_get_irq_data(irq_domain_to_irq(domain, hwirq));
+		if (d || d->domain) {
+			/* things are broken; just report, don't clean up */
+			WARN(1, "error: irq_desc already assigned to a domain");
+			return;
+		}
+		d->domain = domain;
+		d->hwirq = hwirq;
+	}
+
+	mutex_lock(&irq_domain_mutex);
+	list_add(&domain->list, &irq_domain_list);
+	mutex_unlock(&irq_domain_mutex);
+}
+
+/**
+ * irq_domain_del() - Unregister an irq_domain
+ * @domain: ptr to registered irq_domain.
+ */
+void irq_domain_del(struct irq_domain *domain)
+{
+	struct irq_data *d;
+	int hwirq;
+
+	mutex_lock(&irq_domain_mutex);
+	list_del(&domain->list);
+	mutex_unlock(&irq_domain_mutex);
+
+	/* Clear the irq_domain assignments */
+	for (hwirq = 0; hwirq < domain->nr_irq; hwirq++) {
+		d = irq_get_irq_data(irq_domain_to_irq(domain, hwirq));
+		d->domain = NULL;
+	}
+}
+
+#if defined(CONFIG_OF_IRQ)
+/**
+ * irq_create_of_mapping() - Map a linux irq number from a DT interrupt spec
+ *
+ * Used by the device tree interrupt mapping code to translate a device tree
+ * interrupt specifier to a valid linux irq number.  Returns either a valid
+ * linux IRQ number or 0.
+ *
+ * When the caller no longer need the irq number returned by this function it
+ * should arrange to call irq_dispose_mapping().
+ */
+unsigned int irq_create_of_mapping(struct device_node *controller,
+				   const u32 *intspec, unsigned int intsize)
+{
+	struct irq_domain *domain;
+	unsigned long hwirq;
+	unsigned int irq, type;
+	int rc = -EINVAL;
+
+	/* Find a domain which can translate the irq spec */
+	mutex_lock(&irq_domain_mutex);
+	list_for_each_entry(domain, &irq_domain_list, list) {
+		if (!domain->ops->dt_translate)
+			continue;
+		rc = domain->ops->dt_translate(domain, controller,
+					intspec, intsize, &hwirq, &type);
+		if (rc == 0)
+			break;
+	}
+	mutex_unlock(&irq_domain_mutex);
+
+	if (rc != 0)
+		return 0;
+
+	irq = irq_domain_to_irq(domain, hwirq);
+	if (type != IRQ_TYPE_NONE)
+		irq_set_irq_type(irq, type);
+	pr_debug("%s: mapped hwirq=%i to irq=%i, flags=%x\n",
+		 controller->full_name, (int)hwirq, irq, type);
+	return irq;
+}
+EXPORT_SYMBOL_GPL(irq_create_of_mapping);
+
+/**
+ * irq_dispose_mapping() - Discard a mapping created by irq_create_of_mapping()
+ * @irq: linux irq number to be discarded
+ *
+ * Calling this function indicates the caller no longer needs a reference to
+ * the linux irq number returned by a prior call to irq_create_of_mapping().
+ */
+void irq_dispose_mapping(unsigned int irq)
+{
+	/*
+	 * nothing yet; will be filled when support for dynamic allocation of
+	 * irq_descs is added to irq_domain
+	 */
+}
+EXPORT_SYMBOL_GPL(irq_dispose_mapping);
+#endif /* CONFIG_OF_IRQ */