[PATCH v3 25/25] irq_domain: mostly eliminate slow-path revmap lookups

[Grant Likely <grant.likely@secretlab.ca>]

With the current state of irq_domain, the reverse map is always used when
new IRQs get mapped.  This means that the irq_find_mapping() function
can be simplified to always call out to the revmap-specific lookup function.

This patch adds lookup functions for the revmaps that don't yet have one
and removes the slow path lookup from most of the code paths.  The only
place where the slow path legitimately remains is when the linear map
is used with a hwirq number larger than the revmap size.

Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Milton Miller <miltonm@bga.com>
---
 arch/powerpc/sysdev/xics/xics-common.c |    3 -
 include/linux/irqdomain.h              |    3 +-
 kernel/irq/irqdomain.c                 |   94 +++++++++++++++++---------------
 3 files changed, 51 insertions(+), 49 deletions(-)

diff --git a/arch/powerpc/sysdev/xics/xics-common.c b/arch/powerpc/sysdev/xics/xics-common.c
index ea5e204..1d7067d 100644
--- a/arch/powerpc/sysdev/xics/xics-common.c
+++ b/arch/powerpc/sysdev/xics/xics-common.c
@@ -330,9 +330,6 @@ static int xics_host_map(struct irq_domain *h, unsigned int virq,
 
 	pr_devel("xics: map virq %d, hwirq 0x%lx\n", virq, hw);
 
-	/* Insert the interrupt mapping into the radix tree for fast lookup */
-	irq_radix_revmap_insert(xics_host, virq, hw);
-
 	/* They aren't all level sensitive but we just don't really know */
 	irq_set_status_flags(virq, IRQ_LEVEL);
 
diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
index 0b00f83..38314f2 100644
--- a/include/linux/irqdomain.h
+++ b/include/linux/irqdomain.h
@@ -93,6 +93,7 @@ struct irq_domain {
 	struct list_head link;
 
 	/* type of reverse mapping_technique */
+	unsigned int (*revmap)(struct irq_domain *host, irq_hw_number_t hwirq);
 	unsigned int revmap_type;
 	union {
 		struct {
@@ -155,8 +156,6 @@ extern void irq_dispose_mapping(unsigned int virq);
 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);
-extern void irq_radix_revmap_insert(struct irq_domain *host, unsigned int virq,
-				    irq_hw_number_t hwirq);
 extern unsigned int irq_radix_revmap_lookup(struct irq_domain *host,
 					    irq_hw_number_t hwirq);
 extern unsigned int irq_linear_revmap(struct irq_domain *host,
diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
index 5b4fc4d..91c1cb7 100644
--- a/kernel/irq/irqdomain.c
+++ b/kernel/irq/irqdomain.c
@@ -104,6 +104,7 @@ struct irq_domain *irq_domain_add_legacy(struct device_node *of_node,
 	domain->revmap_data.legacy.first_irq = first_irq;
 	domain->revmap_data.legacy.first_hwirq = first_hwirq;
 	domain->revmap_data.legacy.size = size;
+	domain->revmap = irq_domain_legacy_revmap;
 
 	mutex_lock(&irq_domain_mutex);
 	/* Verify that all the irqs are available */
@@ -174,18 +175,35 @@ struct irq_domain *irq_domain_add_linear(struct device_node *of_node,
 	}
 	domain->revmap_data.linear.size = size;
 	domain->revmap_data.linear.revmap = revmap;
+	domain->revmap = irq_linear_revmap;
 	irq_domain_add(domain);
 	return domain;
 }
 
+static unsigned int irq_domain_nomap_revmap(struct irq_domain *domain,
+					    irq_hw_number_t hwirq)
+{
+	struct irq_data *data = irq_get_irq_data(hwirq);
+
+	if (WARN_ON_ONCE(domain->revmap_type != IRQ_DOMAIN_MAP_NOMAP))
+		return irq_find_mapping(domain, hwirq);
+
+	/* Verify that the map has actually been established */
+	if (data && (data->domain == domain) && (data->hwirq == hwirq))
+		return hwirq;
+	return 0;
+}
+
 struct irq_domain *irq_domain_add_nomap(struct device_node *of_node,
 					 const struct irq_domain_ops *ops,
 					 void *host_data)
 {
 	struct irq_domain *domain = irq_domain_alloc(of_node,
 					IRQ_DOMAIN_MAP_NOMAP, ops, host_data);
-	if (domain)
+	if (domain) {
+		domain->revmap = irq_domain_nomap_revmap;
 		irq_domain_add(domain);
+	}
 	return domain;
 }
 
@@ -205,6 +223,7 @@ struct irq_domain *irq_domain_add_tree(struct device_node *of_node,
 					IRQ_DOMAIN_MAP_TREE, ops, host_data);
 	if (domain) {
 		INIT_RADIX_TREE(&domain->revmap_data.tree, GFP_KERNEL);
+		domain->revmap = irq_radix_revmap_lookup;
 		irq_domain_add(domain);
 	}
 	return domain;
@@ -378,6 +397,19 @@ unsigned int irq_create_mapping(struct irq_domain *domain,
 		return 0;
 	}
 
+	switch(domain->revmap_type) {
+	case IRQ_DOMAIN_MAP_LINEAR:
+		if (hwirq < domain->revmap_data.linear.size)
+			domain->revmap_data.linear.revmap[hwirq] = irq;
+		break;
+	case IRQ_DOMAIN_MAP_TREE:
+		mutex_lock(&revmap_trees_mutex);
+		radix_tree_insert(&domain->revmap_data.tree, hwirq,
+				  irq_get_irq_data(irq));
+		mutex_unlock(&revmap_trees_mutex);
+
+		break;
+	}
 	pr_debug("irq: irq %lu on domain %s mapped to virtual irq %u\n",
 		hwirq, domain->of_node ? domain->of_node->full_name : "null", virq);
 
@@ -478,25 +510,27 @@ EXPORT_SYMBOL_GPL(irq_dispose_mapping);
  * irq_find_mapping() - Find a linux irq from an hw irq number.
  * @domain: domain owning this hardware interrupt
  * @hwirq: hardware irq number in that domain space
- *
- * This is a slow path, for use by generic code. It's expected that an
- * irq controller implementation directly calls the appropriate low level
- * mapping function.
  */
 unsigned int irq_find_mapping(struct irq_domain *domain,
 			      irq_hw_number_t hwirq)
 {
-	unsigned int i;
-
-	/* Look for default domain if nececssary */
-	if (domain == NULL)
+	if (!domain)
 		domain = irq_default_domain;
-	if (domain == NULL)
-		return 0;
+	return domain ? domain->revmap(domain, hwirq) : 0;
+}
+EXPORT_SYMBOL_GPL(irq_find_mapping);
 
-	/* legacy -> bail early */
-	if (domain->revmap_type == IRQ_DOMAIN_MAP_LEGACY)
-		return irq_domain_legacy_revmap(domain, hwirq);
+/**
+ * irq_find_mapping_slow() - slow path for finding the irq mapped to a hwirq
+ *
+ * This is the failsafe slow path for finding an irq mapping.  The only time
+ * this will reasonably get called is when the linear map is used with a
+ * hwirq number larger than the size of the reverse map.
+ */
+static unsigned int irq_find_mapping_slow(struct irq_domain *domain,
+					  irq_hw_number_t hwirq)
+{
+	int i;
 
 	/* Slow path does a linear search of the map */
 	for (i = 0; i < irq_virq_count; i++)  {
@@ -506,7 +540,6 @@ unsigned int irq_find_mapping(struct irq_domain *domain,
 	}
 	return 0;
 }
-EXPORT_SYMBOL_GPL(irq_find_mapping);
 
 /**
  * irq_radix_revmap_lookup() - Find a linux irq from a hw irq number.
@@ -537,31 +570,7 @@ unsigned int irq_radix_revmap_lookup(struct irq_domain *domain,
 	 * Else fallback to linear lookup - this should not happen in practice
 	 * as it means that we failed to insert the node in the radix tree.
 	 */
-	return irq_data ? irq_data->irq : irq_find_mapping(domain, hwirq);
-}
-
-/**
- * irq_radix_revmap_insert() - Insert a hw irq to linux irq number mapping.
- * @domain: domain owning this hardware interrupt
- * @virq: linux irq number
- * @hwirq: hardware irq number in that domain space
- *
- * This is for use by irq controllers that use a radix tree reverse
- * mapping for fast lookup.
- */
-void irq_radix_revmap_insert(struct irq_domain *domain, unsigned int virq,
-			     irq_hw_number_t hwirq)
-{
-	struct irq_data *irq_data = irq_get_irq_data(virq);
-
-	if (WARN_ON(domain->revmap_type != IRQ_DOMAIN_MAP_TREE))
-		return;
-
-	if (virq) {
-		mutex_lock(&revmap_trees_mutex);
-		radix_tree_insert(&domain->revmap_data.tree, hwirq, irq_data);
-		mutex_unlock(&revmap_trees_mutex);
-	}
+	return irq_data ? irq_data->irq : irq_find_mapping_slow(domain, hwirq);
 }
 
 /**
@@ -585,14 +594,11 @@ unsigned int irq_linear_revmap(struct irq_domain *domain,
 	if (unlikely(hwirq >= domain->revmap_data.linear.size))
 		return irq_find_mapping(domain, hwirq);
 
-	/* Check if revmap was allocated */
 	revmap = domain->revmap_data.linear.revmap;
-	if (unlikely(revmap == NULL))
-		return irq_find_mapping(domain, hwirq);
 
 	/* Fill up revmap with slow path if no mapping found */
 	if (unlikely(!revmap[hwirq]))
-		revmap[hwirq] = irq_find_mapping(domain, hwirq);
+		revmap[hwirq] = irq_find_mapping_slow(domain, hwirq);
 
 	return revmap[hwirq];
 }
-- 
1.7.5.4