MIPS: i8259: DT support

Support probing the i8259 programmable interrupt controller, as found on
the Malta board, and using its interrupts via device tree.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: devicetree@vger.kernel.org
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Pawel Moll <pawel.moll@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Ian Campbell <ijc+devicetree@hellion.org.uk>
Cc: Kumar Gala <galak@codeaurora.org>
Cc: Qais Yousef <qais.yousef@imgtec.com>
Cc: Andrew Bresticker <abrestic@chromium.org>
Cc: linux-kernel@vger.kernel.org
Patchwork: http://patchwork.linux-mips.org/patch/10114/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/include/asm/i8259.h

@@ -41,6 +41,7 @@ extern int i8259A_irq_pending(unsigned int irq);
 extern void make_8259A_irq(unsigned int irq);
 
 extern void init_i8259_irqs(void);
+extern int i8259_of_init(struct device_node *node, struct device_node *parent);
 
 /*
  * Do the traditional i8259 interrupt polling thing.  This is for the few

arch/mips/kernel/i8259.c

@@ -14,13 +14,16 @@
 #include <linux/interrupt.h>
 #include <linux/irqdomain.h>
 #include <linux/kernel.h>
+#include <linux/of_irq.h>
 #include <linux/spinlock.h>
 #include <linux/syscore_ops.h>
 #include <linux/irq.h>
 
 #include <asm/i8259.h>
 #include <asm/io.h>
 
+#include "../../drivers/irqchip/irqchip.h"
+
 /*
  * This is the 'legacy' 8259A Programmable Interrupt Controller,
  * present in the majority of PC/AT boxes.
@@ -327,7 +330,7 @@ static struct irq_domain_ops i8259A_ops = {
  * driver compatibility reasons interrupts 0 - 15 to be the i8259
  * interrupts even if the hardware uses a different interrupt numbering.
  */
-void __init init_i8259_irqs(void)
+struct irq_domain * __init __init_i8259_irqs(struct device_node *node)
 {
 	struct irq_domain *domain;
 
@@ -336,10 +339,46 @@ void __init init_i8259_irqs(void)
 
 	init_8259A(0);
 
-	domain = irq_domain_add_legacy(NULL, 16, I8259A_IRQ_BASE, 0,
+	domain = irq_domain_add_legacy(node, 16, I8259A_IRQ_BASE, 0,
 				       &i8259A_ops, NULL);
 	if (!domain)
 		panic("Failed to add i8259 IRQ domain");
 
 	setup_irq(I8259A_IRQ_BASE + PIC_CASCADE_IR, &irq2);
+	return domain;
+}
+
+void __init init_i8259_irqs(void)
+{
+	__init_i8259_irqs(NULL);
+}
+
+static void i8259_irq_dispatch(unsigned int irq, struct irq_desc *desc)
+{
+	struct irq_domain *domain = irq_get_handler_data(irq);
+	int hwirq = i8259_irq();
+
+	if (hwirq < 0)
+		return;
+
+	irq = irq_linear_revmap(domain, hwirq);
+	generic_handle_irq(irq);
+}
+
+int __init i8259_of_init(struct device_node *node, struct device_node *parent)
+{
+	struct irq_domain *domain;
+	unsigned int parent_irq;
+
+	parent_irq = irq_of_parse_and_map(node, 0);
+	if (!parent_irq) {
+		pr_err("Failed to map i8259 parent IRQ\n");
+		return -ENODEV;
+	}
+
+	domain = __init_i8259_irqs(node);
+	irq_set_handler_data(parent_irq, domain);
+	irq_set_chained_handler(parent_irq, i8259_irq_dispatch);
+	return 0;
 }
+IRQCHIP_DECLARE(i8259, "intel,i8259", i8259_of_init);