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>

3 files changed, 127 insertions, 0 deletions

diff --git a/kernel/irq/Kconfig b/kernel/irq/Kconfig
index d1d051b38e0b..5a38bf4de641 100644
--- a/kernel/irq/Kconfig
+++ b/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
diff --git a/kernel/irq/Makefile b/kernel/irq/Makefile
index 73290056cfb6..fff17381f0af 100644
--- a/kernel/irq/Makefile
+++ b/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
diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
new file mode 100644
index 000000000000..29c7bd42e25d
--- /dev/null
+++ b/kernel/irq/irqdomain.c
@@ -0,0 +1,122 @@
+#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 */