sh: intc: Handle legacy IRQ reservation in vector map.

Different CPUs will have different starting vectors, with varying
amounts of reserved or unusable vector space prior to the first slot.
This introduces a legacy vector reservation system that inserts itself in
between the CPU vector map registration and the platform specific IRQ
setup. This works fine in practice as the only new vectors that boards
need to establish on their own should be dynamically allocated rather
than arbitrarily assigned. As a plus, this also makes all of the
converted platforms sparseirq ready.
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

arch/sh/kernel/irq.c

@@ -263,6 +263,12 @@ void __init init_IRQ(void)
 {
 	plat_irq_setup();
 
+	/*
+	 * Pin any of the legacy IRQ vectors that haven't already been
+	 * grabbed by the platform
+	 */
+	reserve_irq_legacy();
+
 	/* Perform the machine specific initialisation */
 	if (sh_mv.mv_init_irq)
 		sh_mv.mv_init_irq();

drivers/sh/intc.c

@@ -928,3 +928,28 @@ void destroy_irq(unsigned int irq)
 	__clear_bit(irq, intc_irq_map);
 	spin_unlock_irqrestore(&vector_lock, flags);
 }
+
+int reserve_irq_vector(unsigned int irq)
+{
+	unsigned long flags;
+	int ret = 0;
+
+	spin_lock_irqsave(&vector_lock, flags);
+	if (test_and_set_bit(irq, intc_irq_map))
+		ret = -EBUSY;
+	spin_unlock_irqrestore(&vector_lock, flags);
+
+	return ret;
+}
+
+void reserve_irq_legacy(void)
+{
+	unsigned long flags;
+	int i, j;
+
+	spin_lock_irqsave(&vector_lock, flags);
+	j = find_first_bit(intc_irq_map, nr_irqs);
+	for (i = 0; i < j; i++)
+		__set_bit(i, intc_irq_map);
+	spin_unlock_irqrestore(&vector_lock, flags);
+}

include/linux/sh_intc.h

@@ -84,4 +84,7 @@ struct intc_desc symbol __initdata = {					\
 void __init register_intc_controller(struct intc_desc *desc);
 int intc_set_priority(unsigned int irq, unsigned int prio);
 
+int reserve_irq_vector(unsigned int irq);
+void reserve_irq_legacy(void);
+
 #endif /* __SH_INTC_H */