2 files changed, 18 insertions, 2 deletions

diff --git a/Documentation/devicetree/bindings/arm/versatile-fpga-irq.txt b/Documentation/devicetree/bindings/arm/versatile-fpga-irq.txt
index 9989eda755d9..c9cf605bb995 100644
--- a/Documentation/devicetree/bindings/arm/versatile-fpga-irq.txt
+++ b/Documentation/devicetree/bindings/arm/versatile-fpga-irq.txt
@@ -29,3 +29,8 @@ pic: pic@14000000 {
         clear-mask = <0xffffffff>;
         valid-mask = <0x003fffff>;
 };
+
+Optional properties:
+- interrupts: if the FPGA IRQ controller is cascaded, i.e. if its IRQ
+  output is simply connected to the input of another IRQ controller,
+  then the parent IRQ shall be specified in this property.
diff --git a/drivers/irqchip/irq-versatile-fpga.c b/drivers/irqchip/irq-versatile-fpga.c
index 47a52ab580d8..3ae2bb8d9cf2 100644
--- a/drivers/irqchip/irq-versatile-fpga.c
+++ b/drivers/irqchip/irq-versatile-fpga.c
@@ -9,6 +9,7 @@
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/of_address.h>
+#include <linux/of_irq.h>
 
 #include <asm/exception.h>
 #include <asm/mach/irq.h>
@@ -167,8 +168,12 @@ void __init fpga_irq_init(void __iomem *base, const char *name, int irq_start,
                         f->used_irqs++;
                 }
 
-        pr_info("FPGA IRQ chip %d \"%s\" @ %p, %u irqs\n",
+        pr_info("FPGA IRQ chip %d \"%s\" @ %p, %u irqs",
                 fpga_irq_id, name, base, f->used_irqs);
+        if (parent_irq != -1)
+                pr_cont(", parent IRQ: %d\n", parent_irq);
+        else
+                pr_cont("\n");
 
         fpga_irq_id++;
 }
@@ -180,6 +185,7 @@ int __init fpga_irq_of_init(struct device_node *node,
         void __iomem *base;
         u32 clear_mask;
         u32 valid_mask;
+        int parent_irq;
 
         if (WARN_ON(!node))
                 return -ENODEV;
@@ -193,7 +199,12 @@ int __init fpga_irq_of_init(struct device_node *node,
         if (of_property_read_u32(node, "valid-mask", &valid_mask))
                 valid_mask = 0;
 
-        fpga_irq_init(base, node->name, 0, -1, valid_mask, node);
+        /* Some chips are cascaded from a parent IRQ */
+        parent_irq = irq_of_parse_and_map(node, 0);
+        if (!parent_irq)
+                parent_irq = -1;
+
+        fpga_irq_init(base, node->name, 0, parent_irq, valid_mask, node);
 
         writel(clear_mask, base + IRQ_ENABLE_CLEAR);
         writel(clear_mask, base + FIQ_ENABLE_CLEAR);