[Patch v5 04/12] irqchip: xilinx: Add support for parent intc

[Zubair Lutfullah Kakakhel]

The MIPS based xilfpga platform has the following IRQ structure

Peripherals --> xilinx_intcontroller -> mips_cpu_int controller

Add support for the driver to chain the irq handler

Signed-off-by: Zubair Lutfullah Kakakhel <zubair.kakak...@imgtec.com>

---
V4 -> V5
Rebased to v4.9-rc1
Missing curly braces

V3 -> V4
Clean up if/else when a parent is found
Pass irqchip structure to handler as data

V2 -> V3
Reused existing parent node instead of finding again.
Cleanup up handler based on review

V1 -> V2

No change
---
 drivers/irqchip/irq-xilinx-intc.c | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/drivers/irqchip/irq-xilinx-intc.c 
b/drivers/irqchip/irq-xilinx-intc.c
index 45e5154..dbf8b0c 100644
--- a/drivers/irqchip/irq-xilinx-intc.c
+++ b/drivers/irqchip/irq-xilinx-intc.c
@@ -15,6 +15,7 @@
 #include <linux/of_address.h>
 #include <linux/io.h>
 #include <linux/bug.h>
+#include <linux/of_irq.h>
 
 /* No one else should require these constants, so define them locally here. */
 #define ISR 0x00                       /* Interrupt Status Register */
@@ -154,11 +155,23 @@ static int xintc_map(struct irq_domain *d, unsigned int 
irq, irq_hw_number_t hw)
        .map = xintc_map,
 };
 
+static void xil_intc_irq_handler(struct irq_desc *desc)
+{
+       u32 pending;
+
+       do {
+               pending = xintc_get_irq();
+               if (pending == -1U)
+                       break;
+               generic_handle_irq(pending);
+       } while (true);
+}
+
 static int __init xilinx_intc_of_init(struct device_node *intc,
                                             struct device_node *parent)
 {
        u32 nr_irq;
-       int ret;
+       int ret, irq;
        struct xintc_irq_chip *irqc;
 
        if (xintc_irqc) {
@@ -221,7 +234,16 @@ static int __init xilinx_intc_of_init(struct device_node 
*intc,
                goto err_alloc;
        }
 
-       irq_set_default_host(root_domain);
+       if (parent) {
+               irq = irq_of_parse_and_map(intc, 0);
+               if (irq)
+                       irq_set_chained_handler_and_data(irq,
+                                                        xil_intc_irq_handler,
+                                                        irqc);
+
+       } else {
+               irq_set_default_host(root_domain);
+       }
 
        return 0;
 
-- 
1.9.1