powerpc/mpic: Fix problem that affinity is not updated

Since commit 57b150cc, desc->affinity
of an irq is changed after calling desc->chip->set_affinity.
Therefore we need to fix the irq_choose_cpu() not to depend on the
desc->affinity for new mask.
Signed-off-by: NJiajun Wu <b06378@freescale.com>
Signed-off-by: NLi Yang <leoli@freescale.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/sysdev/mpic.c

@@ -567,13 +567,11 @@ static void __init mpic_scan_ht_pics(struct mpic *mpic)
 #endif /* CONFIG_MPIC_U3_HT_IRQS */
 
 #ifdef CONFIG_SMP
-static int irq_choose_cpu(unsigned int virt_irq)
+static int irq_choose_cpu(const cpumask_t *mask)
 {
-	cpumask_t mask;
 	int cpuid;
 
-	cpumask_copy(&mask, irq_to_desc(virt_irq)->affinity);
-	if (cpus_equal(mask, CPU_MASK_ALL)) {
+	if (cpumask_equal(mask, cpu_all_mask)) {
 		static int irq_rover;
 		static DEFINE_SPINLOCK(irq_rover_lock);
 		unsigned long flags;
@@ -594,20 +592,15 @@ static int irq_choose_cpu(unsigned int virt_irq)
 
 		spin_unlock_irqrestore(&irq_rover_lock, flags);
 	} else {
-		cpumask_t tmp;
-
-		cpus_and(tmp, cpu_online_map, mask);
-
-		if (cpus_empty(tmp))
+		cpuid = cpumask_first_and(mask, cpu_online_mask);
+		if (cpuid >= nr_cpu_ids)
 			goto do_round_robin;
-
-		cpuid = first_cpu(tmp);
 	}
 
 	return get_hard_smp_processor_id(cpuid);
 }
 #else
-static int irq_choose_cpu(unsigned int virt_irq)
+static int irq_choose_cpu(const cpumask_t *mask)
 {
 	return hard_smp_processor_id();
 }
@@ -816,7 +809,7 @@ int mpic_set_affinity(unsigned int irq, const struct cpumask *cpumask)
 	unsigned int src = mpic_irq_to_hw(irq);
 
 	if (mpic->flags & MPIC_SINGLE_DEST_CPU) {
-		int cpuid = irq_choose_cpu(irq);
+		int cpuid = irq_choose_cpu(cpumask);
 
 		mpic_irq_write(src, MPIC_INFO(IRQ_DESTINATION), 1 << cpuid);
 	} else {