irqchip/bcm2835: Add support for being used as a second level controller

The BCM2836 (Raspberry Pi 2) uses two levels of interrupt handling
with the CPU-local interrupts being the root, so we need to register
ours as chained off of the CPU's local interrupt.

Signed-off-by: Eric Anholt <eric@anholt.net>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Cc: linux-rpi-kernel@lists.infradead.org
Cc: Lee Jones <lee@kernel.org>
Cc: Jason Cooper <jason@lakedaemon.net>
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lkml.kernel.org/r/1438902033-31477-3-git-send-email-eric@anholt.net
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

Documentation/devicetree/bindings/interrupt-controller/brcm,bcm2835-armctrl-ic.txt

@@ -5,9 +5,14 @@ The BCM2835 contains a custom top-level interrupt controller, which supports
 controller, or the HW block containing it, is referred to occasionally
 as "armctrl" in the SoC documentation, hence naming of this binding.
 
+The BCM2836 contains the same interrupt controller with the same
+interrupts, but the per-CPU interrupt controller is the root, and an
+interrupt there indicates that the ARMCTRL has an interrupt to handle.
+
 Required properties:
 
-- compatible : should be "brcm,bcm2835-armctrl-ic"
+- compatible : should be "brcm,bcm2835-armctrl-ic" or
+                 "brcm,bcm2836-armctrl-ic"
 - reg : Specifies base physical address and size of the registers.
 - interrupt-controller : Identifies the node as an interrupt controller
 - #interrupt-cells : Specifies the number of cells needed to encode an
@@ -20,6 +25,12 @@ Required properties:
   The 2nd cell contains the interrupt number within the bank. Valid values
   are 0..7 for bank 0, and 0..31 for bank 1.
 
+Additional required properties for brcm,bcm2836-armctrl-ic:
+- interrupt-parent : Specifies the parent interrupt controller when this
+  controller is the second level.
+- interrupts : Specifies the interrupt on the parent for this interrupt
+  controller to handle.
+
 The interrupt sources are as follows:
 
 Bank 0:
@@ -102,9 +113,21 @@ Bank 2:
 
 Example:
 
+/* BCM2835, first level */
 intc: interrupt-controller {
 	compatible = "brcm,bcm2835-armctrl-ic";
 	reg = <0x7e00b200 0x200>;
 	interrupt-controller;
 	#interrupt-cells = <2>;
 };
+
+/* BCM2836, second level */
+intc: interrupt-controller {
+	compatible = "brcm,bcm2836-armctrl-ic";
+	reg = <0x7e00b200 0x200>;
+	interrupt-controller;
+	#interrupt-cells = <2>;
+
+	interrupt-parent = <&local_intc>;
+	interrupts = <8>;
+};

drivers/irqchip/irq-bcm2835.c

@@ -96,6 +96,7 @@ struct armctrl_ic {
 static struct armctrl_ic intc __read_mostly;
 static void __exception_irq_entry bcm2835_handle_irq(
 	struct pt_regs *regs);
+static void bcm2836_chained_handle_irq(unsigned int irq, struct irq_desc *desc);
 
 static void armctrl_mask_irq(struct irq_data *d)
 {
@@ -139,7 +140,8 @@ static const struct irq_domain_ops armctrl_ops = {
 };
 
 static int __init armctrl_of_init(struct device_node *node,
-	struct device_node *parent)
+				  struct device_node *parent,
+				  bool is_2836)
 {
 	void __iomem *base;
 	int irq, b, i;
@@ -168,10 +170,34 @@ static int __init armctrl_of_init(struct device_node *node,
 		}
 	}
 
-	set_handle_irq(bcm2835_handle_irq);
+	if (is_2836) {
+		int parent_irq = irq_of_parse_and_map(node, 0);
+
+		if (!parent_irq) {
+			panic("%s: unable to get parent interrupt.\n",
+			      node->full_name);
+		}
+		irq_set_chained_handler(parent_irq, bcm2836_chained_handle_irq);
+	} else {
+		set_handle_irq(bcm2835_handle_irq);
+	}
+
 	return 0;
 }
 
+static int __init bcm2835_armctrl_of_init(struct device_node *node,
+					  struct device_node *parent)
+{
+	return armctrl_of_init(node, parent, false);
+}
+
+static int __init bcm2836_armctrl_of_init(struct device_node *node,
+					  struct device_node *parent)
+{
+	return armctrl_of_init(node, parent, true);
+}
+
+
 /*
  * Handle each interrupt across the entire interrupt controller.  This reads the
  * status register before handling each interrupt, which is necessary given that
@@ -219,4 +245,15 @@ static void __exception_irq_entry bcm2835_handle_irq(
 		handle_IRQ(irq_linear_revmap(intc.domain, hwirq), regs);
 }
 
-IRQCHIP_DECLARE(bcm2835_armctrl_ic, "brcm,bcm2835-armctrl-ic", armctrl_of_init);
+static void bcm2836_chained_handle_irq(unsigned int irq, struct irq_desc *desc)
+{
+	u32 hwirq;
+
+	while ((hwirq = get_next_armctrl_hwirq()) != ~0)
+		generic_handle_irq(irq_linear_revmap(intc.domain, hwirq));
+}
+
+IRQCHIP_DECLARE(bcm2835_armctrl_ic, "brcm,bcm2835-armctrl-ic",
+		bcm2835_armctrl_of_init);
+IRQCHIP_DECLARE(bcm2836_armctrl_ic, "brcm,bcm2836-armctrl-ic",
+		bcm2836_armctrl_of_init);