genirq: Query arch for number of early descriptors

sparse irq sets up NR_IRQS_LEGACY irq descriptors and archs then go
ahead and allocate more.

Use the unused return value of arch_probe_nr_irqs() to let the
architecture return the number of early allocations. Fix up all users.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Ingo Molnar <mingo@elte.hu>

arch/arm/kernel/irq.c

@@ -157,10 +157,8 @@ void __init init_IRQ(void)
 	struct irq_desc *desc;
 	int irq;
 
-	for (irq = 0; irq < nr_irqs; irq++) {
-		desc = irq_to_desc_alloc_node(irq, 0);
+	for (irq = 0; irq < nr_irqs; irq++)
 		desc->status |= IRQ_NOREQUEST | IRQ_NOPROBE;
-	}
 
 	init_arch_irq();
 }
@@ -169,7 +167,7 @@ void __init init_IRQ(void)
 int __init arch_probe_nr_irqs(void)
 {
 	nr_irqs = arch_nr_irqs ? arch_nr_irqs : NR_IRQS;
-	return 0;
+	return nr_irqs;
 }
 #endif
 

arch/sh/kernel/irq.c

@@ -290,7 +290,7 @@ void __init init_IRQ(void)
 int __init arch_probe_nr_irqs(void)
 {
 	nr_irqs = sh_mv.mv_nr_irqs;
-	return 0;
+	return NR_IRQS_LEGACY;
 }
 #endif
 

arch/x86/kernel/apic/io_apic.c

@@ -3880,7 +3880,7 @@ int __init arch_probe_nr_irqs(void)
 	if (nr < nr_irqs)
 		nr_irqs = nr;
 
-	return 0;
+	return NR_IRQS_LEGACY;
 }
 #endif
 

include/linux/irq.h

@@ -214,6 +214,10 @@ struct irq_chip {
  */
 #include <asm/hw_irq.h>
 
+#ifndef NR_IRQS_LEGACY
+# define NR_IRQS_LEGACY 0
+#endif
+
 #ifndef ARCH_IRQ_INIT_FLAGS
 # define ARCH_IRQ_INIT_FLAGS	0
 #endif

kernel/irq/irqdesc.c

@@ -226,16 +226,16 @@ struct irq_desc * __ref irq_to_desc_alloc_node(unsigned int irq, int node)
 
 int __init early_irq_init(void)
 {
-	int i, node = first_online_node;
+	int i, initcnt, node = first_online_node;
 	struct irq_desc *desc;
 
 	init_irq_default_affinity();
 
-	 /* initialize nr_irqs based on nr_cpu_ids */
-	arch_probe_nr_irqs();
-	printk(KERN_INFO "NR_IRQS:%d nr_irqs:%d\n", NR_IRQS, nr_irqs);
+	/* Let arch update nr_irqs and return the nr of preallocated irqs */
+	initcnt = arch_probe_nr_irqs();
+	printk(KERN_INFO "NR_IRQS:%d nr_irqs:%d %d\n", NR_IRQS, nr_irqs, initcnt);
 
-	for (i = 0; i < NR_IRQS_LEGACY; i++) {
+	for (i = 0; i < initcnt; i++) {
 		desc = alloc_desc(i, node);
 		set_bit(i, allocated_irqs);
 		irq_insert_desc(i, desc);

kernel/softirq.c

@@ -886,9 +886,10 @@ int __init __weak early_irq_init(void)
 	return 0;
 }
 
+#ifdef CONFIG_GENERIC_HARDIRQS
 int __init __weak arch_probe_nr_irqs(void)
 {
-	return 0;
+	return NR_IRQS_LEGACY;
 }
 
 int __init __weak arch_early_irq_init(void)
@@ -900,3 +901,4 @@ int __weak arch_init_chip_data(struct irq_desc *desc, int node)
 {
 	return 0;
 }
+#endif