[RFC PATCH] irqdomain: Fix disposal of mappings for interrupt hierarchies

[Jon Hunter <jonathanh@nvidia.com>]

The function irq_create_of_mapping() is used to create an interrupt
mapping. However, depending on whether the irqdomain, to which the
interrupt belongs, is part of a hierarchy, determines whether the
mapping is created via calling irq_domain_alloc_irqs() or
irq_create_mapping().

To dispose of the interrupt mapping, drivers call irq_dispose_mapping().
However, this function does not check to see if the irqdomain is part
of a hierarchy or not and simply assumes that it was mapped via calling
irq_create_mapping() so calls irq_domain_disassociate() to unmap the
interrupt.

Fix this by checking to see if the irqdomain is part of a hierarchy and
if so call irq_domain_free_irqs() to free/unmap the interrupt.

Signed-off-by: Jon Hunter <jonathanh@nvidia.com>
---

Please note that I have not observed issues with this, but something
that did not make sense to me from looking at the code.

 kernel/irq/irqdomain.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
index caa6a63d26f0..5d89d724a02a 100644
--- a/kernel/irq/irqdomain.c
+++ b/kernel/irq/irqdomain.c
@@ -680,8 +680,12 @@ void irq_dispose_mapping(unsigned int virq)
 	if (WARN_ON(domain == NULL))
 		return;
 
-	irq_domain_disassociate(domain, virq);
-	irq_free_desc(virq);
+	if (irq_domain_is_hierarchy(domain)) {
+		irq_domain_free_irqs(virq, 1);
+	} else {
+		irq_domain_disassociate(domain, virq);
+		irq_free_desc(virq);
+	}
 }
 EXPORT_SYMBOL_GPL(irq_dispose_mapping);
 
-- 
2.1.4