ARM: vic: MULTI_IRQ_HANDLER handler

Add a handler for the VIC that is suitable for MULTI_IRQ_HANDLER
platforms.  This can replace the ASM entry macros for platforms that use
the VIC.

v4:	- rebase ontop of move __exception and friends to
	  asm/exception.h
	- rework polling loop to handle as many irqs as possible in one go
v3:	- simplify irq handling loop as suggested by Grant
	- service interrupts from msb->lsb order
v2:	- allow the handler be used for !CONFIG_OF
	- use irq_domain_to_irq()

Cc: Rob Herring <robherring2@gmail.com>
Acked-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Thomas Abraham <thomas.abraham@linaro.org>
Signed-off-by: Jamie Iles <jamie@jamieiles.com>

arch/arm/common/vic.c

@@ -31,6 +31,7 @@
 #include <linux/device.h>
 #include <linux/amba/bus.h>
 
+#include <asm/exception.h>
 #include <asm/mach/irq.h>
 #include <asm/hardware/vic.h>
 
@@ -428,3 +429,40 @@ int __init vic_of_init(struct device_node *node, struct device_node *parent)
 	return -EIO;
 }
 #endif /* CONFIG OF */
+
+#ifdef CONFIG_MULTI_IRQ_HANDLER
+/*
+ * Handle each interrupt in a single VIC.  Returns non-zero if we've
+ * handled at least one interrupt.  This does a single read of the
+ * status register and handles all interrupts in order from LSB first.
+ */
+static int handle_one_vic(struct vic_device *vic, struct pt_regs *regs)
+{
+	u32 stat, irq;
+	int handled = 0;
+
+	stat = readl_relaxed(vic->base + VIC_IRQ_STATUS);
+	while (stat) {
+		irq = ffs(stat) - 1;
+		handle_IRQ(irq_domain_to_irq(&vic->domain, irq), regs);
+		stat &= ~(1 << irq);
+		handled = 1;
+	}
+
+	return handled;
+}
+
+/*
+ * Keep iterating over all registered VIC's until there are no pending
+ * interrupts.
+ */
+asmlinkage void __exception_irq_entry vic_handle_irq(struct pt_regs *regs)
+{
+	int i, handled;
+
+	do {
+		for (i = 0, handled = 0; i < vic_id; ++i)
+			handled |= handle_one_vic(&vic_devices[i], regs);
+	} while (handled);
+}
+#endif /* CONFIG_MULTI_IRQ_HANDLER */

arch/arm/include/asm/hardware/vic.h

@@ -45,8 +45,11 @@
 #include <linux/types.h>
 
 struct device_node;
+struct pt_regs;
+
 void vic_init(void __iomem *base, unsigned int irq_start, u32 vic_sources, u32 resume_sources);
 int vic_of_init(struct device_node *node, struct device_node *parent);
+void vic_handle_irq(struct pt_regs *regs);
 
 #endif /* __ASSEMBLY__ */
 #endif