irqdomain: make irq_linear_revmap() a fast path again

Over the years, irq_linear_revmap() gained tests and checks to make sure
callers were using it safely, which while important, also make it less
of a fast path. After the irqdomain refactoring done recently, it is now
possible to make irq_linear_revmap() a fast path again. This patch moves
irq_linear_revmap() to the header file and makes it a static inline so
that interrupt controller drivers using a linear mapping can decode the
virq from a hwirq in just a couple of instructions.

Signed-off-by: Grant Likely <grant.likely@linaro.org>

1 files changed, 16 insertions, 3 deletions

diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
index 6efbeccac56c..c983ed18c332 100644
--- a/include/linux/irqdomain.h
+++ b/include/linux/irqdomain.h
@@ -176,6 +176,22 @@ extern void irq_domain_associate_many(struct irq_domain *domain,
 extern unsigned int irq_create_mapping(struct irq_domain *host,
                                        irq_hw_number_t hwirq);
 extern void irq_dispose_mapping(unsigned int virq);
+
+/**
+ * irq_linear_revmap() - Find a linux irq from a hw irq number.
+ * @domain: domain owning this hardware interrupt
+ * @hwirq: hardware irq number in that domain space
+ *
+ * This is a fast path alternative to irq_find_mapping() that can be
+ * called directly by irq controller code to save a handful of
+ * instructions. It is always safe to call, but won't find irqs mapped
+ * using the radix tree.
+ */
+static inline unsigned int irq_linear_revmap(struct irq_domain *domain,
+                                             irq_hw_number_t hwirq)
+{
+        return hwirq < domain->revmap_size ? domain->linear_revmap[hwirq] : 0;
+}
 extern unsigned int irq_find_mapping(struct irq_domain *host,
                                      irq_hw_number_t hwirq);
 extern unsigned int irq_create_direct_mapping(struct irq_domain *host);
@@ -189,9 +205,6 @@ static inline int irq_create_identity_mapping(struct irq_domain *host,
         return irq_create_strict_mappings(host, hwirq, hwirq, 1);
 }
 
-extern unsigned int irq_linear_revmap(struct irq_domain *host,
-                                      irq_hw_number_t hwirq);
-
 extern const struct irq_domain_ops irq_domain_simple_ops;
 
 /* stock xlate functions */