[PATCH] add the ability to template irq handlers in the generic irq code

[James Bottomley <James.Bottomley@SteelEye.com>]

On parisc, we have the issue that function call pointers are hugely
expensive, so we'd like to minimise their use in the interrupts.
Unfortunately, this involves directly calling the ack/eoi functions
instead of indirecting.  To permit this without losing the advantages of
centrally managed irq code, I introduced template builders for irq
handlers.  This allows us to construct special handlers on parisc that
don't indirect through function call pointers.

Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>

---
James

Index: parisc-2.6/kernel/irq/chip.c
===================================================================
--- parisc-2.6.orig/kernel/irq/chip.c	2006-09-12 09:17:53.000000000 -0700
+++ parisc-2.6/kernel/irq/chip.c	2006-09-12 09:19:46.000000000 -0700
@@ -17,6 +17,90 @@
 
 #include "internals.h"
 
+/* Helpers for constructing IRQ handlers */
+
+#ifdef CONFIG_SMP
+#define HANDLE_PERCPU_IRQ(NAME, ACK, EOI)				\
+void fastcall								\
+handle_percpu_irq##NAME(unsigned int irq, struct irq_desc *desc,	\
+			struct pt_regs *regs)				\
+{									\
+	irqreturn_t action_ret;						\
+									\
+	kstat_this_cpu.irqs[irq]++;					\
+									\
+	ACK(desc, irq);							\
+									\
+	action_ret = handle_IRQ_event(irq, regs, desc->action);		\
+	if (!noirqdebug)						\
+		note_interrupt(irq, desc, action_ret, regs);		\
+									\
+	EOI(desc,irq);							\
+}
+#else
+#define HANDLE_PERCPU_IRQ(NAME, ACK, END)
+#endif /* CONFIG_SMP */
+
+#define HANDLE_LEVEL_IRQ(NAME, MASK, UNMASK)				\
+void fastcall								\
+handle_level_irq##NAME(unsigned int irq, struct irq_desc *desc,		\
+			struct pt_regs *regs)				\
+{									\
+	unsigned int cpu = smp_processor_id();				\
+	struct irqaction *action;					\
+	irqreturn_t action_ret;						\
+									\
+	spin_lock(&desc->lock);						\
+	MASK(desc, irq);						\
+									\
+	if (unlikely(desc->status & IRQ_INPROGRESS))			\
+		goto out;						\
+	desc->status &= ~(IRQ_REPLAY | IRQ_WAITING);			\
+	kstat_cpu(cpu).irqs[irq]++;					\
+									\
+	/*								\
+	 * If its disabled or no action available			\
+	 * keep it masked and get out of here				\
+	 */								\
+	action = desc->action;						\
+	if (unlikely(!action || (desc->status & IRQ_DISABLED))) {	\
+		desc->status |= IRQ_PENDING;				\
+		goto out;						\
+	}								\
+									\
+	desc->status |= IRQ_INPROGRESS;					\
+	desc->status &= ~IRQ_PENDING;					\
+	spin_unlock(&desc->lock);					\
+									\
+	action_ret = handle_IRQ_event(irq, regs, action);		\
+	if (!noirqdebug)						\
+		note_interrupt(irq, desc, action_ret, regs);		\
+									\
+	spin_lock(&desc->lock);						\
+	desc->status &= ~IRQ_INPROGRESS;				\
+out:									\
+	UNMASK(desc,irq);						\
+	spin_unlock(&desc->lock);					\
+}
+
+#define HANDLE_SPECIFIC_IRQ(NAME, ACK, EOI, HANDLER)			\
+void fastcall								\
+handle_specific_irq##NAME(unsigned int irq, struct irq_desc *desc,	\
+			  struct pt_regs *regs)				\
+{									\
+	irqreturn_t action_ret;						\
+									\
+	kstat_this_cpu.irqs[irq]++;					\
+									\
+	ACK(desc, irq);							\
+									\
+	action_ret = HANDLER(irq, desc->action->dev_id, regs);		\
+	if (!noirqdebug)						\
+		note_interrupt(irq, desc, action_ret, regs);		\
+									\
+	EOI(desc,irq);							\
+}
+
 /**
  *	set_irq_chip - set the irq chip for an irq
  *	@irq:	irq number
@@ -186,6 +270,24 @@ static inline void mask_ack_irq(struct i
 	}
 }
 
+static inline void unmask_enabled_irq(struct irq_desc *desc, int irq)
+{
+	if (!(desc->status & IRQ_DISABLED) && desc->chip->unmask)
+		desc->chip->unmask(irq);
+}
+
+static inline void ack_irq(struct irq_desc *desc, int irq)
+{
+	if (desc->chip->ack)
+		desc->chip->ack(irq);
+}
+
+static inline void eoi_irq(struct irq_desc *desc, int irq)
+{
+	if (desc->chip->eoi)
+		desc->chip->eoi(irq);
+}
+
 /**
  *	handle_simple_irq - Simple and software-decoded IRQs.
  *	@irq:	the interrupt number
@@ -241,46 +343,7 @@ out_unlock:
  *	it after the associated handler has acknowledged the device, so the
  *	interrupt line is back to inactive.
  */
-void fastcall
-handle_level_irq(unsigned int irq, struct irq_desc *desc, struct pt_regs *regs)
-{
-	unsigned int cpu = smp_processor_id();
-	struct irqaction *action;
-	irqreturn_t action_ret;
-
-	spin_lock(&desc->lock);
-	mask_ack_irq(desc, irq);
-
-	if (unlikely(desc->status & IRQ_INPROGRESS))
-		goto out;
-	desc->status &= ~(IRQ_REPLAY | IRQ_WAITING);
-	kstat_cpu(cpu).irqs[irq]++;
-
-	/*
-	 * If its disabled or no action available
-	 * keep it masked and get out of here
-	 */
-	action = desc->action;
-	if (unlikely(!action || (desc->status & IRQ_DISABLED))) {
-		desc->status |= IRQ_PENDING;
-		goto out;
-	}
-
-	desc->status |= IRQ_INPROGRESS;
-	desc->status &= ~IRQ_PENDING;
-	spin_unlock(&desc->lock);
-
-	action_ret = handle_IRQ_event(irq, regs, action);
-	if (!noirqdebug)
-		note_interrupt(irq, desc, action_ret, regs);
-
-	spin_lock(&desc->lock);
-	desc->status &= ~IRQ_INPROGRESS;
-out:
-	if (!(desc->status & IRQ_DISABLED) && desc->chip->unmask)
-		desc->chip->unmask(irq);
-	spin_unlock(&desc->lock);
-}
+HANDLE_LEVEL_IRQ(, mask_ack_irq, unmask_enabled_irq)
 
 /**
  *	handle_fasteoi_irq - irq handler for transparent controllers
@@ -416,7 +479,6 @@ out_unlock:
 	spin_unlock(&desc->lock);
 }
 
-#ifdef CONFIG_SMP
 /**
  *	handle_percpu_IRQ - Per CPU local irq handler
  *	@irq:	the interrupt number
@@ -425,25 +487,19 @@ out_unlock:
  *
  *	Per CPU interrupts on SMP machines without locking requirements
  */
-void fastcall
-handle_percpu_irq(unsigned int irq, struct irq_desc *desc, struct pt_regs *regs)
-{
-	irqreturn_t action_ret;
+HANDLE_PERCPU_IRQ(, ack_irq, eoi_irq)
 
-	kstat_this_cpu.irqs[irq]++;
-
-	if (desc->chip->ack)
-		desc->chip->ack(irq);
-
-	action_ret = handle_IRQ_event(irq, regs, desc->action);
-	if (!noirqdebug)
-		note_interrupt(irq, desc, action_ret, regs);
-
-	if (desc->chip->eoi)
-		desc->chip->eoi(irq);
+#ifdef ARCH_HAS_IRQ_HANDLERS
+#include <asm/irq-handlers.h>
+#else
+static inline char *arch_handle_irq_name(void fastcall (*handle)(unsigned int,
+							struct irq_desc *,
+							struct pt_regs *))
+{
+	return NULL;
 }
+#endif
 
-#endif /* CONFIG_SMP */
 
 void
 __set_irq_handler(unsigned int irq,
@@ -533,5 +589,5 @@ handle_irq_name(void fastcall (*handle)(
 	if (handle == handle_bad_irq)
 		return "bad    ";
 
-	return NULL;
+	return arch_handle_irq_name(handle);
 }