[PATCH] irqchip: versatile FPGA: support cascaded interrupts from DT

[Linus Walleij]

The Versatile FPGA interrupt controller supports cascading interrupts,
i.e. that its output is connected to the input of another interrupt
controller. This makes it possible to pass a parent interrupt from
the device tree and print it in the boot log if applicable.

Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Linus Walleij <linus.walleij@xxxxxxxxxx>
---
TGLX: I can take this through ARM SoC if you're happy with it
and prefer it that way, but it merges just as fine as it is on
the IRQ tree.
---
 .../devicetree/bindings/arm/versatile-fpga-irq.txt        |  5 +++++
 drivers/irqchip/irq-versatile-fpga.c                      | 15 +++++++++++++--
 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 9989eda..c9cf605 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 47a52ab..3ae2bb8 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);
-- 
1.8.3.1

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