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>

2 files changed, 163 insertions, 1 deletions

diff --git a/kernel/irq/Makefile b/kernel/irq/Makefile
index 73290056cfb..aa8feed23b0 100644
--- a/kernel/irq/Makefile
+++ b/kernel/irq/Makefile
@@ -1,5 +1,5 @@
 
-obj-y := irqdesc.o handle.o manage.o spurious.o resend.o chip.o dummychip.o devres.o
+obj-y := irqdesc.o handle.o manage.o spurious.o resend.o chip.o dummychip.o devres.o irqdomain.o
 obj-$(CONFIG_GENERIC_IRQ_CHIP) += generic-chip.o
 obj-$(CONFIG_GENERIC_IRQ_PROBE) += autoprobe.o
 obj-$(CONFIG_PROC_FS) += proc.o
diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
new file mode 100644
index 00000000000..a7cc91084f6
--- /dev/null
+++ b/kernel/irq/irqdomain.c
@@ -0,0 +1,162 @@
+
+#include <linux/irq.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)
+{
+	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)
+{
+	mutex_lock(&irq_domain_mutex);
+	list_del(&domain->list);
+	mutex_unlock(&irq_domain_mutex);
+}
+
+/**
+ * irq_domain_map() - Allocate and/or increment a reference to a hwirq
+ *
+ * TODO: Establish a linux irq number mapping for a hardware irq.  If the
+ * mapping already exists, then increment the reference count and return the
+ * linux irq number.
+ *
+ * At the moment this function is an empty stub since irq_domain initially
+ * only supports the common case of mapping hw irq numbers into a contiguous
+ * range of pre-allocated linux irq_descs based at irq_domain->irq_base.  When
+ * irq_domains are extended either to support non-contiguous mappings (ie. to
+ * support MSI interrupts) or to remove preallocation of all irq_descs (as
+ * powerpc does so that irq_descs are only allocated for in-use irq inputs),
+ * then this function will be extended to implement the irq_desc allocation
+ * and reference counting.
+ *
+ * Any caller to this function must arrange to also call irq_domain_unmap()
+ * if the irq ever becomes unused again.
+ */
+unsigned int irq_domain_map(struct irq_domain *domain, irq_hw_number_t hwirq)
+{
+	int irq = irq_domain_to_irq(domain, hwirq);
+	struct irq_data *d = irq_get_irq_data(irq);
+
+	d->domain = domain;
+	d->hwirq = hwirq;
+
+	return irq;
+}
+
+/**
+ * irq_domain_unmap() - Release a reference to a hwirq
+ *
+ * TODO: decrement the reference count on a hardware irq number.  If the ref
+ * count reaches zero, then the irq_desc can be freed.
+ *
+ * At the moment this function is an empty stub.  See the comment on
+ * irq_domain_map() for details.
+ */
+void irq_domain_unmap(struct irq_domain *domain, irq_hw_number_t hwirq)
+{
+	int irq = irq_domain_to_irq(domain, hwirq);
+	struct irq_data *d = irq_get_irq_data(irq);
+
+	d->domain = NULL;
+}
+
+#if defined(CONFIG_OF_IRQ) && !defined(CONFIG_PPC)
+
+/*
+ * A handful of architectures use NO_IRQ, which must be used to avoid breaking
+ * things when using the device tree.  This is intended to be temporary until
+ * the remaining NO_IRQ users can be removed
+ */
+#ifndef NO_IRQ
+#define NO_IRQ 0
+#endif
+
+/**
+ * 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;
+	irq_hw_number_t hwirq;
+	unsigned int irq, type;
+	int rc = -ENODEV;
+
+	/* 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 defined(CONFIG_MIPS) || defined(CONFIG_MICROBLAZE)
+	/*
+	 * Temporary: preserves current behaviour until mips/microblaze
+	 * register an irq_domain
+	 */
+	if (rc != 0) {
+		pr_debug("%s: fallback mapping for irq=%i\n",
+			 controller->full_name, irq);
+		return intspec[0];
+	}
+#else
+	if (rc != 0)
+		return NO_IRQ;
+#endif
+
+	irq = irq_domain_map(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)
+{
+	struct irq_data *d = irq_get_irq_data(irq);
+	irq_domain_unmap(d->domain, d->hwirq);
+}
+EXPORT_SYMBOL_GPL(irq_dispose_mapping);
+
+#endif